NON-NATURAL MICROBIAL ORGANISMS WITH IMPROVED ENERGETIC EFFICIENCY

SUMMARY OF INVENTION

The invention provides non-natural microbial organisms containing enzymatic pathways for enhancing carbon flux to acetyl-CoA, or oxaloacetate and acetyl-CoA, and methods for their use to produce bio-products, and bio-products made using such microbial organisms.

Generally, microbial organisms are provided that make acetyl-CoA, or oxaloacetate and acetyl-CoA, have a phosphoketolase pathway (PK pathway) and has (i) a genetic modification that enhances the activity of the non-phosphotransferase system (non-PTS) for sugar uptake, and/or (ii) a genetic modification(s) to the organism's electron transport chain (ETC) that enhances efficiency of ATP production, that enhances availability of reducing equivalents or both. The modifications enhance energetic efficiency of the modified microbial organism. Optionally, the organism can include (iii) a genetic modification that maintains, attenuates, or eliminates the activity of a phosphotransferase system (PTS) for sugar uptake.

Through experimental studies associated with the current disclosure, it has been discovered that the PK pathway in combination with (i) and/or (ii), and optionally (iii) enhanced carbon flux through acetyl-CoA, or both oxaloacetate and acetyl-CoA. In turn, this increased the pool of acetyl-CoA and oxaloacetate useful for enhancing the production of a desired product or its intermediate (a bioderived compound) while advantageously minimizing undesired compounds. Therefore, the non-natural microbial organisms containing enzymatic pathways for enhancing carbon flux through acetyl-CoA, or both oxaloacetate and acetyl-CoA, with the modifications as described herein can increase the production of intermediates or products such as alcohols (e.g., propanediol or a butanediol), glycols, organic acids, alkenes, dienes (e.g., butadiene), isoprenoids (e.g. isoprene), organic amines, organic aldehydes, vitamins, nutraceuticals, and pharmaceuticals.

Therefore, in one aspect (e.g., a first aspect) the invention provides a non-natural microbial organism that includes (a) a pathway to acetyl-CoA, or both oxaloacetate and acetyl-CoA, comprising a phosphoketolase pathway, and (b) a genetic modification that increases non-PTS activity for sugar uptake. Optionally, the organism can include (c) a genetic modification that maintains, attenuates, or eliminates a PTS activity for sugar uptake. The genetic modification includes those that change an enzyme or protein of the PTS or non-PTS, its activity, a gene-encoding that enzyme or protein, or the gene's expression. The organism can also have a pathway to a bioderived compound, and a modification to the non-PTS to increase non-PTS activity that improves production of the bioderived compound via improvements in synthesis of acetyl-CoA, or both oxaloacetate and acetyl-CoA, which serve as intermediates. Modification to the non-PTS can balance the fluxes from phosphoenolpyruvate (PEP) into oxaloacetate and pyruvate, which offers an improvement over organisms that rely on an endogenous PTS system for sugar uptake, and which can advantageously lead into the bioderived compound pathway.

The PTS and non-PTS can allow for uptake of primarily C5, C6 or C12 sugars and their oligomers. Non-natural microbial organism having a PTS for sugar (e.g., C6, C12, sugar alcohols, and amino sugars) uptake are able to phosphorylate sugars by conversion of PEP into pyruvate. The non-PTS allows for uptake of sugars via a facilitator or a permease and subsequent phosphorylation via a kinase. The non-PTS further allows uptake of C5 sugars such as xylose, disaccharides such as lactose, melibiose, and maltose. Other substrates such as ascorbate may be recognized by a specific PTS or non-PTS enzyme or protein. Phosphorylated sugar then goes through the majority of reactions in glycolysis to generate reducing equivalents and ATP that are associated with the organism's electron transport chain (ETC).

Illustrative PK pathways, can include the following enzymes:

both fructose-6-phosphate phosphoketolase (1T) and a phosphotransacetylase (1V);

all three of fructose-6-phosphate phosphoketolase (1T), an acetate kinase (1W), and an acetyl-CoA transferase, an acetyl-CoA synthetase, or an acetyl-CoA ligase (1X);

both xylulose-5-phosphate phosphoketolase (1U) and a phosphotransacetylase (1V); or

all three of xylulose-5-phosphate phosphoketolase (1U), an acetate kinase (1W), and an acetyl-CoA transferase, an acetyl-CoA synthetase, or an acetyl-CoA ligase (1X).

A non-natural microbial organism of the first aspect with the (a) a pathway to oxaloacetate, acetyl-CoA or both, comprising a phosphoketolase, and (b) a genetic modification to enhance non-PTS activity, can optionally further include one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance availability of reducing equivalents, or both.

In another aspect (e.g., a second aspect) the invention provides a non-natural microbial organism that includes (a) a pathway to oxaloacetate, acetyl-CoA or both, comprising a phosphoketolase pathway, and (b) one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance availability of reducing equivalents, or both. For example, modifications as described herein that increase the number of protons translocated per electron pair that reaches cytochrome oxidases or complex IV of the electron transport chain provide increased protons that are used by ATP synthase to produce ATP. Consequently, by increasing the amount of ATP generated per pair of electrons channeled through the electron transport chain, the energetic efficiency (also referred to as P/O ratio) of the cell is increased. Similarly, modifications that attenuate or eliminate NADH dehydrogenases that do not transport or inefficiently transport protons increases the NADH pool available for the more efficient NADH dehydrogenases, e.g. nuo. Again, the energetic efficiency of the cell is increased.

Organisms of the second aspect may include a pathway for assimilation of an alternate carbon source (e.g., methanol, syngas, glycerol, formate, methane), for example, if the PTS and non-PTS are modified, not present in the organism, or otherwise do not provide the desired influx of a hydrocarbon energy source. Accordingly, organisms making oxaloacetate and/or acetyl-CoA and that contain a phosphoketolase pathway can also comprise a pathway for using non-sugar carbon substrates such as glycerol, syngas, formate, methane and methanol.

Modifications that enhance the organism's ETC function include attenuation or elimination of expression or activity of an enzyme or protein that competes with efficient electron transport chain function. Examples are attenuation or elimination of NADH-dehydrogenases that do not translocate protons or attenuation or elimination of cytochrome oxidases that have lower efficiency of proton translocation per pair of electrons. ETC modifications also include enhancing function of an enzyme or protein of the organism's ETC, particularly when such a function is rate-limiting. Examples in bacteria of modifications that enhance an enzymes or protein are increasing activity of an enzyme or protein of Complex I of the ETC and attenuating or eliminating the global negative regulatory factor arcA.

Microbial organisms having a PK pathway can also synthesize succinyl-CoA subsequent to the synthesis of acetyl-CoA and oxaloacetate, and succinyl-CoA can further be used in a product pathway to a bioderived compound. Oxaloacetate is produced anaplerotically from phosphoenolpyruvate or from pyruvate. Succinyl-CoA is produced either by oxidative TCA cycle whereby both acetyl-CoA and oxaloacetate are used as precursors, via the reductive TCA cycle where oxaloacetate is used as the precursor or by a combination of both oxidative and reductive TCA branches. Microbial organisms having a PK pathway can optionally further include increased activity of one or more enzymes that can enable higher flux into oxaloacetate which, when combined with acetyl-CoA, leads to higher flux through oxidative TCA and the products derived therefrom, or increased flux for producing succinyl-CoA via the reductive TCA branch. Examples of enzymes that can have increased activity in the cells include PEP synthetase, pyruvate carboxylase, and phosphoenolpyruvate carboxylase, which can be present in the microbial organisms of the first or second aspect.

Optionally, organisms having a PK pathway can further include attenuation or elimination of one or more endogenous enzymes in order to further enhance carbon flux through acetyl-CoA, or both acetyl-CoA and oxaloacetate, or a gene disruption of one or more endogenous nucleic acids encoding such enzymes. For example, the attenuated or eliminated endogenous enzyme could be one of the isozymes of pyruvate kinase, and its deletion can be used in microbial organisms of the first or second aspect or both.

The enhanced carbon flux through acetyl-CoA, or both oxaloacetate and acetyl-CoA, in the microbial organisms described herein can be used for production of a bioderived compound. Accordingly, in further aspects, the microbial organism can further include a pathway capable of producing a desired bioderived compound. That is, the microbial organism of the first or second aspect can further include one or more pathway enzyme(s) that promote production of the bioderived compound.

Bioderived compounds include alcohols, glycols, organic acids, alkenes, dienes, isoprenoids, olefins, organic amines, organic aldehydes, vitamins, nutraceuticals and pharmaceuticals. In some embodiments, the bioderived compound is 1,3-butanediol, crotyl alcohol, butadiene, 3-buten-2-ol, 1,4-butanediol, adipate, 6-aminocaproate, caprolactam, hexamethylenediamine, propylene, isoprene, methacrylic acid, 2-hydroxyisobutyric acid, or an intermediate thereto. One or more pathway enzyme(s) can utilize enhanced carbon flux through acetyl-CoA, or both oxaloacetate and acetyl-CoA, as precursor promoting the production of the bioderived compound.

BRIEF DESCRIPTION OF THE FIGURES

Compounds as described FIGS. 1-14 are abbreviated as follows. MeOH or MEOH=methanol; Fald=formaldehyde; GLC=glucose; G6P=glucose-6-phosphate; H6P=hexulose-6-phosphate; F6P=fructose-6-phosphate; FDP=fructose diphosphate or fructose-1,6-diphosphate; 13DPG: 1,3-diphosphoglycerate, 3PG=3-phosphoglycerate, 2PG=2-phosphoglycerate, DHA=dihydroxyacetone; DHAP=dihydroxyacetone phosphate; G3P=glyceraldehyde-3-phosphate; PEP: phosphoenolpyruvate, PYR=pyruvate; ACTP=acetyl-phosphate; ACCOA=acetyl-CoA; AACOA=acetoacetyl-CoA; MALCOA=malonyl-CoA; E4P=erythrose-4-phosphate: Xu5P=xyulose-5-phosphate; Ru5P=ribulose-5-phosphate; S7P=sedoheptulose-7-phosphate: R5P=ribose-5-phosphate; XYL=xylose; TCA=tricarboxylic acid; PEP=Phosphoenolpyruvate; OAA=Oxaloacetate; MAL=malate; CIT=citrate; ICIT=isocitrate; AKG=alpha-ketoglutarate; FUM=Fumarate; SUCC=Succinate; SUCCOA=Succinyl-CoA; 3HBCOA=3-hydroxybutyryl-CoA; 3-HB=3-hydroxybutyrate; 3HBALD=3-hydroxybutyraldehyde; 13BDO=1,3-butanediol; CROTCOA=crotonyl-CoA; CROT=crotonate; CROTALD=crotonaldehyde; CROTALC=crotyl alcohol; CROT-Pi=crotyl phosphate; CROT-PPi=crotyl diphosphate or 2-butenyl-4-diphosphate.

FIG. 1 shows exemplary metabolic pathways enabling the conversion of exemplary PTS and non-PTS sugars such as glucose (GLC) and xylose (XYL) to acetyl-CoA (ACCOA) as well as the pathways for assimilation of other carbon sources such as methanol and glycerol to form acetyl-CoA. Arrows with alphabetical designations represent enzymatic transformations of a precursor compound to an intermediate compound. Enzymatic transformations shown are carried out by the following enzymes: A) methanol dehydrogenase, B) 3-hexulose-6-phosphate synthase, C) 6-phospho-3-hexuloisomerase, D) dihydroxyacetone synthase, E) formate dehydrogenase (NAD or NADP-dependent), F) sugar permease or facilitator protein (non-PTS), G) sugar kinase (non-pts), H) PTS system of sugar transport, I) ribulose-5-phosphate-3-epimerase, J) transketolase, K) ribulose-5-phosphate isomerase, L) transaldolase, M) transketolase, Q) pyruvate formate lyase, R) pyruvate dehydrogenase, pyruvate ferredoxin oxidoreductase, or pyruvate:NADP+ oxidoreductase, S) formate dehydrogenase, T) fructose-6-phosphate phosphoketolase, U) xylulose-5-phosphate phosphoketolase, V) phosphotransacetylase, W) acetate kinase, X) acetyl-CoA transferase, synthetase, or ligase, Y) lower glycolysis including glyceraldehyde-3-phosphate dehydrogenase, Z) fructose-6-phosphate aldolase. FIG. 1 also shows exemplary endogenous enzyme targets for optional attenuation or disruption. The endogenous enzyme targets include DHA kinase, methanol oxidase (AOX), PQQ-dependent methanol dehydrogenase (PQQ) and/or DHA synthase. FIG. 1 also shows acetyl-CoA can be led into an into another “intermediate pathway” as depicted in FIG. 4, or into “compound pathways” (bioderived compound pathways), such as those depicted in FIGS. 5-11.

FIG. 2 shows pathways that enable formation of oxaloacetate. The enzymatic transformations are: A) PEP Carboxylase, B) Pyruvate carboxylase, C) Pyruvate kinase and D) PEP synthetase, E) Malic enzyme

FIG. 3 shows various enzymes and proteins (components) of the electron transport chain (ETC). As an example, the ETC of E. coli is shown. NADH dehydrogenases form the Complex I of the electron transport chain and transfer electrons to the quinone pool. Components of the ETC that do not translocate protons are targets for attenuation or elimination of expression or activity in the non-natural microbial organisms in order to increase efficiency of ATP production. Cytochrome oxidases receive electrons from the quinone pool and reduce oxygen. Cytochrome oxidases that do no translocate protons or reduce lower number of protons per pair of electrons are targets for attenuation or elimination of expression or activity in the non-natural microbial organisms for increasing efficiency of ATP production in the cells.

FIG. 4 shows exemplary metabolic pathways enabling the conversion of the glycolysis intermediate glyceraldehye-3-phosphate (G3P) to acetyl-CoA (ACCOA) and/or succinyl-CoA (SUCCOA). The enzymatic transformations shown can be carried out by the following enzymes: A) PEP carboxylase or PEP carboxykinase, B) malate dehydrogenase, C) fumarase, D) fumarate reductase, E) succinyl-CoA synthetase or transferase, F) pyruvate kinase or PTS-dependent substrate import, G) pyruvate dehydrogenase, pyruvate formate lyase, or pyruvate:ferredoxin oxidoreductase, H) citrate synthase, I) aconitase, J) isocitrate dehydrogenase, K) alpha-ketoglutarate dehydrogenase, L) pyruvate carboxylase, M) malic enzyme, N) isocitrate lyase and malate synthase.

FIG. 5 shows exemplary pathways enabling production of 1,3-butanediol, crotyl alcohol, and butadiene from acetyl-CoA. The 1,3-butanediol, crotyl alcohol, and butadiene production can be carried out by the following enzymes: A) acetyl-CoA carboxylase, B) an acetoacetyl-CoA synthase, C) an acetyl-CoA:acetyl-CoA acyltransferase, D) an acetoacetyl-CoA reductase (ketone reducing), E) a 3-hydroxybutyryl-CoA reductase (aldehyde forming), F) a 3-hydroxybutyryl-CoA hydrolase, transferase or synthetase, G) a 3-hydroxybutyrate reductase, H) a 3-hydroxybutyraldehyde reductase, I) chemical dehydration or FIG. 6, J) a 3-hydroxybutyryl-CoA dehydratase, K) a crotonyl-CoA reductase (aldehyde forming), L) a crotonyl-CoA hydrolase, transferase or synthetase, M) a crotonate reductase, N) a crotonaldehyde reductase, O) a crotyl alcohol kinase, P) a 2-butenyl-4-phosphate kinase, Q) a butadiene synthase, R) a crotyl alcohol diphosphokinase, S) chemical dehydration or a crotyl alcohol dehydratase, T) a butadiene synthase (monophosphate), T) a butadiene synthase (monophosphate), U) a crotonyl-CoA reductase (alcohol forming), and V) a 3-hydroxybutyryl-CoA reductase (alcohol forming).

FIG. 6 shows exemplary pathways for converting 1,3-butanediol to 3-buten-2-ol and/or butadiene. The 3-buten-2-ol and butadiene production can be carried out by the following enzymes: A. 1,3-butanediol kinase, B. 3-hydroxybutyrylphosphate kinase, C. 3-hydroxybutyryldiphosphate lyase, D. 1,3-butanediol diphosphokinase, E. 1,3-butanediol dehydratase, F. 3-hydroxybutyrylphosphate lyase, G. 3-buten-2-ol dehydratase or chemical dehydration.

FIG. 7 shows exemplary pathways enabling production of 1,4-butanediol from succinyl-CoA. The 1,4-butanediol production can be carried out by the following enzymes: A) a succinyl-CoA transferase or a succinyl-CoA synthetase, B) a succinyl-CoA reductase (aldehyde forming), C) a 4-HB dehydrogenase, D) a 4-HB kinase, E) a phosphotrans-4-hydroxybutyrylase, F) a 4-hydroxybutyryl-CoA reductase (aldehyde forming), G) a 1,4-butanediol dehydrogenase, H) a succinate reductase, I) a succinyl-CoA reductase (alcohol forming), J) a 4-hydroxybutyryl-CoA transferase or 4-hydroxybutyryl-CoA synthetase, K) a 4-HB reductase, L) a 4-hydroxybutyryl-phosphate reductase, and M) a 4-hydroxybutyryl-CoA reductase (alcohol forming).

FIG. 8 shows exemplary pathways enabling production of adipate, 6-aminocaproic acid, caprolactam, and hexamethylenediamine from succinyl-CoA and acetyl-CoA. Adipate, 6-aminocaproic acid, caprolactam, and hexamethylenediamine production can be carried out by the following enzymes: A) 3-oxoadipyl-CoA thiolase, B) 3-oxoadipyl-CoA reductase, C) 3-hydroxyadipyl-CoA dehydratase, D) 5-carboxy-2-pentenoyl-CoA reductase, E) adipyl-CoA reductase (aldehyde forming), F) 6-aminocaproate transaminase or 6-aminocaproate dehydrogenase, G) 6-aminocaproyl-CoA/acyl-CoA transferase or 6-aminocaproyl-CoA synthase, H) amidohydrolase, I) spontaneous cyclization, J) 6-aminocaproyl-CoA reductase (aldehyde forming), K) HMDA transaminase or HMDA dehydrogenase, L) Adipyl-CoA hydrolase, adipyl-CoA ligase, adipyl-CoA transferase, or phosphotransadipylase/adipate kinase.

FIG. 9 shows exemplary pathways enabling production of 3-hydroxyisobutyrate and methacrylic acid from succinyl-CoA. 3-Hydroxyisobutyrate and methacrylic acid production are carried out by the following enzymes: A) Methylmalonyl-CoA mutase, B) Methylmalonyl-CoA epimerase, C) Methylmalonyl-CoA reductase (aldehyde forming), D) Methylmalonate semialdehyde reductase, E) 3-hydroxyisobutyrate dehydratase, F) Methylmalonyl-CoA reductase (alcohol forming).

FIG. 10 shows exemplary pathways enabling production of 2-hydroxyisobutyrate and methacrylic acid from acetyl-CoA. 2-Hydroxyisobutyrate and methacrylic acid production can be carried out by the following enzymes: A) acetyl-CoA:acetyl-CoA acyltransferase, B) acetoacetyl-CoA reductase (ketone reducing), C) 3-hydroxybutyrl-CoA mutase, D) 2-hydroxyisobutyryl-CoA dehydratase, E) methacrylyl-CoA synthetase, hydrolase, or transferase, F) 2-hydroxyisobutyryl-CoA synthetase, hydrolase, or transferase.

FIG. 11 shows exemplary pathways enabling production of 2,4-pentadieonate (2,4PD)/butadiene from acetyl-coA. The following enzymes can be used for 2,4-PD/butadiene production. Enzyme names: A. Acetaldehyde dehydrogenase, B. 4-hydroxy 2-oxovalerate aldolase, C. 4-hydroxy 2-oxovalerate dehydratase, D. 2-oxopentenoate reductase, E. 2-hydroxypentenoate dehydratase, F. 2,4-pentadienoate decarboxylase, G. 2-oxopentenoate ligase, H. 2-oxopentenoate: acetyl CoA transferase, I. 2-oxopentenoyl-CoA reductase, J. 2-hydroxypentenoate ligase, K. 2-hydroxypentenoate:acetyl-CoA CoA transferase, L. 2-hydroxypentenoyl-CoA dehydratase, M. 2,4-Pentadienoyl-CoA hydrolase, N. 2,4-Pentadienoyl-CoA:acetyl CoA transferase

FIGS. 12A-C show the increase in BDO titers and reduction in C3 byproducts such as alanine and pyruvate when PK is expressed in a strain that employs both the PTS and the Non-PTS system of glucose transport. The diamond and the square symbols represent the fermentation runs where PK was not expressed. The crosses and the triangles represent the fermentation runs where PK was expressed with a p115 promoter.

FIG. 13 illustrates steps in the construction expression mutants of native glk and Zymomonas mobilis glf that were inserted into the PTS− cells and selection of those mutants that had an improved growth rate on glucose as described in Example 1.

FIG. 14A shows growth rate curves of expression variants of glk-glf as described in Example 1 and FIG. 14B shows maximum growth rates of select variants and parent strains.

DETAILED DESCRIPTION

The present disclosure provides metabolic and biosynthetic processes and non-natural microbial organisms capable of enhancing carbon flux through acetyl-CoA, or both oxaloacetate and acetyl-CoA, synthesized using a pathway comprising phosphoketolase for producing acetyl-CoA (a PK pathway). The non-natural microbial organisms can utilize the enhanced pool of acetyl-CoA, or both oxaloacetate and acetyl-CoA, in a further compound pathway to produce a bio-derived product.

To generate enhanced carbon flux through acetyl-CoA, or both oxaloacetate and acetyl-CoA, a pathway comprising phosphoketolase is used in conjunction with (i) a non-phosphotransferase system (non-PTS) for sugar uptake comprising a genetic modification to a non-PTS component to increase non-PTS activity, and/or (ii) one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance availability or synthesis of reducing equivalents, or both. Optionally, the non-natural microbial organisms can include (iii) a genetic modification of a phosphotransferase system (PTS) component that attenuates or eliminates a PTS activity.

A first aspect of the disclosure is directed to a non-natural microbial organism having (a) a pathway to acetyl-CoA, or both oxaloacetate and acetyl-CoA, comprising a phosphoketolase, (b) a non-PTS for sugar uptake comprising a genetic modification to a non-PTS component to increase non-PTS activity. Optionally, the organism can also include a genetic modification of a PTS component that attenuates or eliminates a PTS activity.

The pathway comprising phosphoketolase for producing acetyl-CoA (PK pathway), and a sugar uptake system (e.g., non-PTS) are exemplified in FIG. 1. This non-natural organism can use acetyl-CoA, or both oxaloacetate and acetyl-CoA (see FIG. 4), in a “compound pathway” to produce a bio-derived product (such as an alcohol, a glycol, an organic acid, an alkene, a diene, an organic amine, an organic aldehyde, a vitamin, a nutraceutical or a pharmaceutical). Therefore the non-natural microbial organisms can further include product pathway enzymes to carry out conversion of acetyl-CoA, or both oxaloacetate and acetyl-CoA, to the desired product (e.g., combining the relevant pathways of FIG. 1 or 4, with a pathway of FIGS. 5-11).

Even further, this non-natural microbial organism can optionally include one or more of the following: (e) one or more modification(s) to the organism's electron transport chain, (f) a carbon substrate (e.g., methanol, syngas, etc.) utilization pathway to increase carbon flux towards acetyl-CoA, or both oxaloacetate and acetyl-CoA, (g) a pathway synthesizing succinyl-CoA as precursors further to the synthesis of acetyl-CoA and oxaloacetate, (h) attenuation or elimination of one or more endogenous enzymes, which enhances carbon flux through acetyl-CoA, or both oxaloacetate and acetyl-CoA, (e.g., pyruvate kinase attenuation), and (i) increased activity of one or more endogenous or heterologous enzymes that can enable higher flux to oxaloacetate or succinyl-CoA (e.g., increases in PEP synthetase, pyruvate carboxylase, or phosphoenolpyruvate carboxylase).

A second aspect of the disclosure is directed to a non-natural microbial organism having (a) a pathway to oxaloacetate, acetyl-CoA or both, comprising phosphoketolase, and (b) one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance synthesis or availability of reducing equivalents, or both. In this non-natural microbial organism, modifications to the PTS and non-PTS for sugar uptake are not necessary, but optionally can be included. As an alternative to, or in addition to the PTS and non-PTS, a (c) carbon substrate (e.g., methanol, syngas, etc.) utilization pathway to provide carbon flux towards oxaloacetate, acetyl-CoA or both, can be present in the non-natural organism. This non-natural microbial organism can use the oxaloacetate, acetyl-CoA or both, in a (d) product pathway to produce a bio-derived product (such as an alcohol, a glycol, etc.) that includes product pathway enzymes. Even further, this non-natural microbial organism can optionally include, (e) a pathway synthesizing oxaloacetate or succinyl-CoA as precursors, (f) attenuation or elimination of one or more endogenous enzymes, which enhances carbon flux through acetyl-CoA (e.g., pyruvate kinase attenuation), or (g) increased activity of one or more enzymes that can enable higher flux to oxaloacetate or succinyl-CoA (e.g., increases in PEP synthetase, pyruvate carboxylase, or phosphoenolpyruvate carboxylase).

The pathway comprising phosphoketolase can include one, two, three, four, or five, or more than five enzymes to promote flux to acetyl-CoA, or both oxaloacetate and acetyl-CoA.

Some exemplary embodiments of the acetyl-CoA pathway comprising phosphoketolase can be understood with reference to FIG. 1. For example, in some embodiments, the acetyl-CoA pathway comprises a pathway selected from: (1) 1T and 1V; (2) 1T, 1W, and 1X; (3) 1U and 1V; (4) 1U, 1W, and 1X; wherein 1T is a fructose-6-phosphate phosphoketolase, wherein 1U is a xylulose-5-phosphate phosphoketolase, wherein 1V is a phosphotransacetylase, wherein 1W is an acetate kinase, wherein 1X is an acetyl-CoA transferase, an acetyl-CoA synthetase, or an acetyl-CoA ligase. In some embodiments, the acetyl-CoA pathway comprises (1) 1T and 1V. In some embodiments, the acetyl-CoA pathway comprises (2) 1T, 1W, and 1X. The enzymes sets (1) and (2) can define a pathway from fructose-6-phosphate (F6P) to acetyl-CoA (AcCoA).

In some embodiments, the acetyl-CoA comprises (3) 1U and 1V. In some embodiments, the acetyl-CoA pathway comprises (4) 1U, 1W, and 1X. The enzymes sets (3) and (4) can define a pathway from fructose-6-phosphate (F6P) to acetyl-CoA (AcCoA). In some embodiments, an enzyme of the methanol metabolic pathway or the acetyl-CoA pathway is encoded by at least one exogenous nucleic acid and is expressed in a sufficient amount to enhance carbon flux through acetyl-CoA.

Any of the acetyl-CoA pathways comprising phosphoketolase (1) 1T and 1V; (2) 1T, 1W, and 1X; (3) 1U and 1V; (4) 1U, 1W, and 1X can be present in organisms of the first or second aspect of the disclosure.

The PTS and non-PTS can allow for uptake of primarily C5, C6 or C12 sugars and their oligomers. Organisms having a PTS for sugar (e.g., C6, C12, sugar alcohols, and amino sugars) uptake are able to phosphorylate sugars by conversion of PEP into pyruvate.

The non-PTS, on the other hand, uses different sugar uptake enzymes and proteins (components) than the PTS, and this affects the balance of intracellular sugar-derived intermediates that are brought into the cell. In addition to glucose, the non-PTS allows for more robust import of C5 sugars such as xylose, disaccharides such as lactose, melibiose, maltose, and glycerol via a facilitator or a permease and subsequent phopshorylation via a kinase. Other substrates such as ascorbate may be recognized by a specific PTS or non-PTS.

With reference to FIG. 1, in some embodiments, the non-natural microorganism comprises an acetyl-CoA, or both oxaloacetate and acetyl-CoA pathway (also see FIG. 4) comprising phosphoketolase, a non-PTS for sugar uptake, and a PTS for sugar uptake that comprises a permease or a facilitator protein (1F), and a kinase (1G).

The non-PTS can include a non-PTS permease (e.g., facilitator protein), a non-PTS sugar kinase or a facilitator protein, and these can modified for increased expression or activity in a non-natural microbial organism having (a) a pathway to acetyl-CoA, or both oxaloacetate and acetyl-CoA, comprising a phosphoketolase. The non-PTS permease can be a glucose permease, and the non-PTS sugar kinase can be a glucokinase. An exemplary glucose facilitator proteins is encoded by Zymomonas mobilis glf. An exemplary glucokinase is encoded by E. coli glk and an exemplary permease is encoded by E. coli galP.

The genetic modification to a non-PTS component to increase non-PTS activity can be any one or more of a variety of forms. For example, in some embodiments, the non-PTS component is under the expression of a promoter comprising one or more genetic modifications that enhance its expression. The enhanced expression can result in an increase in activity of the rate of sugar uptake to the cells. For example, the rate of uptake can be at least 10%, at least 25%, at least 50%, at least 75%, at least 100%, at least 125% or at least 150% greater than the rate of sugar uptake of an organism that does not include the non-PTS genetic modification. Exemplary rate of uptake increases can be in the range of 10% to 150%, or from 25% to 125%.

An organism with a genetic modification to a non-PTS enzyme or protein to increase non-PTS activity prevents PEP conversion into pyruvate associated with sugar phosphorylation and therefore allows for a better balance of fluxes into oxaloacetate and pyruvate from PEP. Phosphorylated sugar then goes through the majority of reactions in glycolysis to generate reducing equivalents and ATP that are associated with the organism's electron transport chain (ETC).

In some embodiments, the non-natural microbial organism comprises a genetic modification of a PTS component that attenuates or eliminates a PTS activity. In a non-natural microbial organism system that includes non-PTS for sugar uptake, an attenuating or eliminating genetic modification of a PTS component can shift the sugar uptake towards the non-PTS, thereby providing an improved pool of sugar derived intermediates than can be utilized by the pathway comprising phosphoketolase for the production of acetyl-CoA, or both oxaloacetate and acetyl-CoA.

In embodiments wherein the non-natural organism has one or more genetic modifications that attenuates or eliminates expression or activity of a PTS component.

The PTS system comprises Enzyme I (EI), histidine phosphocarrier protein (HPr), Enzyme II (EII), and transmembrane Enzyme II C (EIIC). The system allows specific uptake of sugars into the cell, with the sugars transported up at a concentration gradient along phosphorylation. Phosphoenolpyruvate (PEP) is the phosphate donor, with the phosphate transferred via the (non-sugar specific) enzymes EI and HPr to the enzyme complex EII. The enzyme complex EII includes components A, B and C. These components can be domains of composite proteins, according to sugar specificity and the type of bacteria. Component/domain C is a permease and anchored to the cytoplasmic membrane. In E. coli, the glucose PTS EIIA is a soluble protein, and the EIIB/C is membrane bound. In E. coli the two non-specific components are encoded by ptsI (Enzyme I) and ptsH (HPr). The sugar-dependent components are encoded by crr and ptsG. Any one or more of these PTS enzymes or proteins (components) can be targeted for attenuated or eliminated expression or activity. Alternatively, the non-natural organism having attenuated or eliminated expression of PTS enzymes or proteins is caused by alteration, such as deletion of, the ptsI gene.

The PTS can include proteins specific for the uptake of certain sugar species. These are generally known as “permeases” or “facilitator proteins.” For example, the PTS can comprises one or more proteins selected from the group consisting of glucose permease (EIICBA), glucosamine permease (EIICBA), N-acetyl muramic acid-specific permease (EIIBC component), mannitol permease, galactomannan permease, trehalose permease, maltose permease, fructose permease, mannose permease, N-acetylglucosamine permease, (EIICB component), fructose permease, sucrose permease (high affinity), sucrose permease (low affinity), lichenan permease, and β-glucoside permease. The non-natural microbial organisms of the disclosure can include attenuated or eliminated expression of one or more proteins specific for the uptake of certain sugar species.

Proteins of the PTS can be encoded by genes of the microorganism. For example, glucose permease can be encoded by PtsG, the glucosamine permease can be encoded by GamP, the N-acetyl muramic acid-specific permease can be encoded by MurP, the mannitol permease can be encoded by MtlA or MtlF, the galactomannan permease can be encoded by GmuA, GmuB, or GmuC, the trehalose permease can be encoded by TreP, the maltose permease can be encoded by MalP, the fructose permease can be encoded by FruA, the mannose permease is encoded can be ManP, the N-acetylglucosamine permease can be encoded by NagP, the fructose permease can be encoded by LevD, LevE, LevF, LevG, the sucrose permease (high affinity) can be encoded by SacP, the sucrose permease (low affinity) can be encoded by SacY, the lichenan permease can be encoded by LicA, LicB, or LicC, and the β-glucoside permease can be encoded by BglP. The non-natural microbial organisms of the disclosure can include genetic modification of one or more of these genes for attenuated or eliminated expression of their corresponding proteins.

Non-natural microbial organisms of the disclosure can also include one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance availability or synthesis of reducing equivalents, or both. For example, the second aspect of the disclosure provides a non-natural microbial organism that includes (a) a pathway to oxaloacetate, acetyl-CoA or both, comprising a phosphoketolase, and (b) one or more modification(s) to the organism's electron transport chain.

Optionally one or more modification(s) to the organism's electron transport chain can also be used along with the non-PTS for sugar uptake comprising a genetic modification to a non-PTS component to increase non-PTS activity, in a non-natural microbial organism having a PK pathway. For example, in an organism having flux through phosphoketolase, the non-oxidative pentose phosphate pathway does not generate any ATP or reducing equivalents and it is therefore desirable to have the electron transport chain operate efficiently. Such modifications to the ETC are useful when the organism uses the PK pathway irrespective of the carbon source used. For example, such modifications will be useful when methanol, methane, formate, syngas or glycerol are used as the carbon sources.

Modifications that enhance the organism's electron transport chain function include attenuation of enzymes, proteins or co-factors that compete with efficient electron transport chain function. Examples are attenuation of NADH-dehydrogenases that do not translocate protons or an attenuation of cytochrome oxidases that have lower efficiency of proton translocation per pair of electrons. Modifications that enhance the organism's electron transport chain function include enhancing function of enzymes, proteins or co-factors of the organism's electron transport chain particularly when such a function is rate-limiting. Examples in bacteria of modifications that enhance enzymes, proteins or co-factors are increasing activity of NADH dehydrogenases of the electron transport chain or the desired cytochrome oxidase cyo and attenuating the global negative regulatory factor arcA.

In some embodiments, the invention provides a non-naturally occurring microbial organism having attenuation or elimination of endogenous enzyme expression or activity that compete with efficient electron transport chain function, thereby enhancing carbon flux through acetyl-CoA or oxaloacetate into the desired products. Elimination of endogenous enzyme expression can be carried out by gene disruption of one or more endogenous nucleic acids encoding such enzymes. For example, in some aspects the endogenous enzymes targeted for modification include genes such as ndh, wrbA, mdaB, yhdH, yieF, ytfG, qor, ygiN, appBC and cydAB in E. coli. Similar non-efficient components of the electron transport chain can be eliminated or modified from other organisms.

The electron transport chain of Escherichia coli has multiple NADH dehydrogenases and cytochrome oxidases, with varying ability to translocate protons. For example, NADH dehydrogenase II in E. coli is an NADH consuming system that is not linked with proton translocation (H+/2e−=0) whereas NADH dehydrogenase I encoded by nuo is reported to translocate 4 protons per pair of electrons. The major role of Ndh-II is to oxidize NADH and to feed electrons into the respiratory chain (Yun et al., 2005). The affinity of NdhII for NADH is relatively low (Hayashi et al., 1989), it has been suggested that NdhII may operate to regulate the NADH pool independently of energy generation and is likely to be important when the capacity of bacteria to generate energy exceeds demand. The ndh gene has been shown to be repressed by the fnr gene product in such a way that the expression is optimal under conditions of high oxygen concentrations. The deletion of ndh would thus help in improving the redox availability and therefore the ATP availability of the cell upon oxidation of this NADH. Similarly, there are several other NADH dehydrogenases that are not known to translocate any protons and thus do not help in ATP production, example, those encoded by wrbA, mdaB, yhdH, yieF, ytfG, qor in E. coli. Homologues of these can be found in other organisms and eliminated to improve the ATP production for every unit of oxygen consumed.

On the electron output side of the electron transport chain, multiple cytochrome oxidases are present that have different energy-conserving efficiencies. The cytochrome bo complex, encoded by the cyo operon, actively pumps electrons over the membrane and results in an H+/2e− stoichiometry of 4. The cytochrome bd-I complex does not actively pump protons, but due to the oxidation of the quinol on the periplasmic side of the membrane and subsequent uptake of protons from the cytoplasmic side of the membrane which are used in the formation of water, the net electron transfer results in a H+/2e− stoichiometry of 2. This is encoded by the cyd operon. Till recently, the proton translocation stoichiometry of cytochrome bd-II oxidase, encoded by appBC, was not known but it has now been established that this oxidase is non-electrogenic [Bekker M, de V S, Ter B A, Hellingwerf K J, de Mattos M J. 2009. Respiration of Escherichia coli can be fully uncoupled via the nonelectrogenic terminal cytochrome bd-II oxidase. J Bacteriol 191:5510-5517.]. These genes are normally induced upon entry into stationary phase or under conditions of carbon and phosphate starvation Atlung et al., 1997 (Atlung T, Knudsen K, Heerfordt L, Brondsted L. 1997. Effects of sigmaS and the transcriptional activator AppY on induction of the Escherichia coli hya and cbdAB-appA operons in response to carbon and phosphate starvation. J Bacteriol 179:2141-2146.). Deletion of the cytochrome oxidases appBC and cydAB will therefore improve the ATP formation per NADH via oxidative phosphorylation, thus increasing efficiency of ATP production. The quinol monooxygenase, ygiN, also falls in this category.

In addition to or as an alternative to attenuating such host functions, an enhanced electron transport function can be provided in a non-naturally organism that contains an acetyl-CoA, or acetyl-CoA and oxaloacetate pathway by providing a modification that increases an enzyme, protein or co-factor function of the organism's electron transport chain to enhance efficiency of ATP production, production of reducing equivalents or both, particularly when such functions are rate-limiting. Examples in bacteria of such target genes include those that comprise Complex I (which can be increased by such methods as increased copy number, overexpression or enhanced activity variants) of the electron transport chain and the global negative regulatory factor arcA (which can be attenuated).

Additionally, given the non-NADH generating nature of the PK pathway, it is important that mechanisms for generating NADH are introduced into recombinant organisms for making reduced products. For example, a 14BDO producing organism (described in Example XI) requires conversion of pyruvate into acetyl-CoA. When a PK is introduced into this organism, it is important that the pyruvate to acetyl-CoA conversion takes place either through pyruvate dehydrogenase or by a combination of pyruvate formate lyase and an NADH-generating formate dehydrogenase. Native formate dehydrogenase(s) that do not generate NADH can be optionally deleted. In E. coli these formate dehydrogenases are formate dehydrogenase H, N and O.

In some other embodiments, the invention provides a process with the described acetyl-CoA pathway to have a lower aeration process compared to an organism that does not have such a pathway.

Since flux through phosphoketolase does not produce NADH, any organism that has flux through PK should require less oxygen to regenerate NAD. For example, the stoichiometry of making 14BDO via only the oxidative TCA cycle is shown below:

C₆H₁₂O₆+0.5O₂→C₄H₁₀O₂+2CO₂+H₂O

In contrast, an organism that can increase its BDO yield by using PK will have the following stoichiometry, still using only the oxidative TCA for routing carbon into the BDO pathway:

C₆H₁₂O₆+0.313O₂→1.034C₄H₁₀O₂+1.864CO₂+0.830H₂O

This organism has 60% of the oxygen demand per glucose metabolized as compared to an organism that does not use PK. This lowers the aeration/oxygen requirements in a fermentation process while increasing the product yields.

A reducing equivalent can also be readily obtained from a glycolysis intermediate by any of several central metabolic reactions including glyceraldehyde-3-phosphate dehydrogenase, pyruvate dehydrogenase, pyruvate formate lyase and NAD(P)-dependent formate dehydrogenase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase. Additionally, reducing equivalents can be generated from glucose 6-phosphate-1-dehydrogenase and 6-phosphogluconate dehydrogenase of the pentose phosphate pathway. Overall, at most twelve reducing equivalents can be obtained from a C6 glycolysis intermediate (e.g., glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate) and at most six reducing equivalents can be generated from a C3 glycolysis intermediate (e.g., dihydroxyacetone phosphate, glyceraldehyde-3-phosphate).

Optionally, non-natural microbial organisms of the disclosure having a PK pathway can also use both acetyl-CoA and oxaloacetate or succinyl-CoA as precursors to product pathways. Oxaloacetate is produced anaplerotically from phosphoenolpyruvate or from pyruvate. Succinyl-CoA is produced either by oxidative TCA cycle whereby both acetyl-CoA and oxaloacetate are used as precursors, via the reductive TCA cycle where oxaloacetate is used as the precursor or by a combination of both oxidative and reductive TCA branches. Non-natural microbial organisms of the first, or second aspect can further use both acetyl-CoA and oxaloacetate or succinyl-CoA as precursors. Genetic modifications can include increasing the activity of one or more endogenous or heterologous enzymes, or attenuating or eliminating one or more endogenous enzymes to increase flux into oxaloacetate or succinyl-CoA.

In some embodiments, the invention provides a non-natural organism having increased activity of one or more endogenous enzymes, that combined with the acetyl-CoA (PK) pathway, enables higher flux to the product. These enzymes are targeted towards increased flux into oxaloacetate which, when combined with acetyl-CoA leads to higher flux through oxidative TCA and the products derived therefrom. Alternatively, the increased flux into oxaloacetate can be used for producing succinyl-CoA via the reductive TCA branch. This includes PEP synthetase, pyruvate carboxylase, and phosphoenolpyruvate carboxylase. This increased activity can be achieved by increasing the expression of an endogenous or exogenous gene either by overexpressing it under a stronger promoter or by expressing an extra copy of the gene or by adding copies of a gene not expressed endogenously.

Embodiments of the disclosure provide non-naturally organism comprising a phosphoketolase (PK)-containing pathway that makes acetyl-CoA, or acetyl-CoA and oxaloacetate, and one or more of the following: (i) a genetic modification that enhances the activity of the non-PTS system for sugar uptake, and/or (ii) one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance availability of reducing equivalents, or both, and further, one or more modifications that enhance flux to oxaloacetate or succinyl-CoA. In turn, these modifications can enhance production of bioproducts in combination with the product pathways.

The one or more modifications that enhance flux to oxaloacetate or succinyl-CoA can be any one or more of the following.

In some embodiments, the non-natural microbial organism further includes attenuation of pyrvuate kinase. Pyruvate kinase leads to the formation of pyruvate from PEP, concomitantly converting ADP into ATP.

PEP+ADP pyruvate+ATP+H⁺

Attenuation or deletion of this enzyme will allow more PEP to be converted into oxaloacetate (and not into pyruvate that subsequently gets converted into acetyl-CoA). This leads to a better balance of carbon flux into oxaloacetate and into acetyl-CoA. In E. coli, this reaction is carried out by two isozymes, pykA and pykF. The deletion of even one of them can have the desired effect of reducing PEP flux into pyruvate and increasing it into oxaloacetate.

In some embodiments, the non-natural microbial organism increases phosphoenol-pyruvate availability by enhancing PEP synthetase activity in a strain that requires oxaloacetate as a bioproduct precursor. This enzyme converts pyruvate back into PEP with the cost of two ATP equivalents as shown below. This is a mechanism that the cell can use to balance the flux that goes into acetyl-CoA versus the carbon flux that goes into PEP and then onto oxaloacetate.

pyruvate+ATP⁺H₂O<=>phosphoenolpyruvate+AMP+phosphate+2H⁺

In some embodiments, the non-natural microbial organism increases oxaloacetate availability via enhancing pyruvate carboxylase activity in a strain that requires oxaloacetate as a bioproduct precursor. Pyruvate carboxylase catalyzes the carboxylation of pyruvate into oxaloacetate using biotin and ATP as cofactors as shown below.

pyruvate+hydrogen carbonate+ATP→oxaloacetate+ADP+phosphate+H+

Pyruvate carboxylase is present in several bacteria such as Corynebacterium glumaticum and Mycobacteria, but not present in E. coli. Pyruvate carboxylase can be expressed heterologously in E. coli via methods well known in the art. Optimal expression of this enzyme would allow for sufficient generation of oxaloacetate and is also expected to reduce the formation of byproducts such as alanine, pyruvate, acetate and ethanol.

In some embodiments, the non-natural microbial organism increases oxaloacetate availability via enhancing phosphoenolpyruvate (PEP) carboxylase activity in a strain that requires oxaloacetate as a bioproduct precursor. The gene ppc encodes for phosphoenolpyruvate (PEP) carboxylase activity. The net reaction involves the conversion of PEP and bicarbonate into oxaloacetate and phosphate. The overexpression of PEP carboxylase leads to conversion of more phosphoenolpyruvate (PEP) into OAA, thus reducing the flux from PEP into pyruvate, and subsequently into acetyl-CoA. This leads to increased flux into the TCA cycle and thus into the pathway. Further, this overexpression also decreases the intracellular acetyl-CoA pools available for the ethanol-forming enzymes to work with, thus reducing the formation of ethanol and acetate. The increased flux towards oxaloacetate will also reduce pyruvate and alanine byproducts.

In some embodiments, the non-natural microbial organism increases phosphoenol-pyruvate availability via enhancing PEP carboxykinase (pck) activity in a strain that requires oxaloacetate as a bioproduct precursor. PEP carboxykinase is an alternative enzyme for converting phosphoenolpyruvate to oxaloacetate, which simultaneously forms an ATP while carboxylating PEP. In most organisms PEP carboxykinase serves a gluconeogenic function and converts oxaloacetate to PEP at the expense of one ATP. S. cerevisiae is one such organism whose native PEP carboxykinase, PCK1, serves a gluconeogenic role (Valdes-Hevia et al., FEBS Lett. 258:313-316 (1989). E. coli is another such organism, as the role of PEP carboxykinase in producing oxaloacetate is believed to be minor when compared to PEP carboxylase, which does not form ATP, possibly due to the higher K_mfor bicarbonate of PEP carboxykinase (Kim et al., Appl. Environ. Microbiol. 70:1238-1241 (2004)). Nevertheless, activity of the native E. coli PEP carboxykinase from PEP towards oxaloacetate has been recently demonstrated in ppc mutants of E. coli K-12 (Kwon et al., J. Microbiol. Biotechnol. 16:1448-1452 (2006)). These strains exhibited no growth defects and had increased succinate production at high NaHCO₃concentrations. In some embodiments, the non-natural microbial organism can increase its oxaloacetate availability by increasing expression or activity of malic enzyme. Malic enzyme can be applied to convert CO₂and pyruvate to malate at the expense of one reducing equivalent. Malate can then be converted into oxaloacetate via native malate dehydrogenases. Malic enzymes for this purpose can include, without limitation, malic enzyme (NAD-dependent) and malic enzyme (NADP-dependent). For example, one of the E. coli malic enzymes (Takeo, J. Biochem. 66:379-387 (1969)) or a similar enzyme with higher activity can be expressed to enable the conversion of pyruvate and CO₂to malate. By fixing carbon to pyruvate as opposed to PEP, malic enzyme allows the high-energy phosphate bond from PEP to be conserved by pyruvate kinase whereby ATP is generated in the formation of pyruvate or by the phosphotransferase system for glucose transport. Although malic enzyme is typically assumed to operate in the direction of pyruvate formation from malate, overexpression of the NAD-dependent enzyme, encoded by maeA, has been demonstrated to increase succinate production in E. coli while restoring the lethal delta pfl-delta ldhA phenotype (inactive or deleted pfl and ldhA) under anaerobic conditions by operating in the carbon-fixing direction (Stols and Donnelly, Appl. Environ. Microbiol. 63(7) 2695-2701 (1997)). A similar observation was made upon overexpressing the malic enzyme from Ascaris suum in E. coli (Stols et al., Appl. Biochem. Biotechnol. 63-65(1), 153-158 (1997)). The second E. coli malic enzyme, encoded by maeB, is NADP-dependent and also decarboxylates oxaloacetate and other alpha-keto acids (Iwakura et al., J. Biochem. 85(5):1355-65 (1979)).

In some embodiments, the non-natural microbial organism increases the non oxidative pentose phosphate pathway activity, ribose-5-phosphate isomerase (encoded by rpiAB in E. coli), ribulose-5-phosphate epimerase (rpe), transaldolase (talAB) and transketolase (tktAB), to convert C5 sugars to glycolytic intermediates glyceraldehyde-3-phosphate and fructose-6-phosphate that are substrates for the phosphoketolase pathway.

The non oxidative pentose phosphate pathway comprises numerous enzymes that have the net effect of converting C5 sugar intermediates into C3 and C6 glycolytic intermediates, namely, glyceraldehyde-3-phosphate and fructose-6-phosphate. The enzymes included in the non-oxidative PP branch are ribose-5-phosphate isomerase (encoded by rpiAB in E. coli), ribulose-5-phosphate epimerase (rpe), transaldolase (talAB), and transketolase (tktAB).

Ribose-5-phopshate epimerase catalyzes the interconversion of ribose-5-phosphate and ribulose-5-phosphate. There are two distinct ribose-5-phosphate isomerases present in E. coli. RpiA encodes for the constitutive ribose-5-phosphate isomerase A and typically accounts for more than 99% of the ribose-5-phosphate isomerase activity in the cell. The inducible ribose-5-phosphate isomerase B can substitute for RpiA's function if its expression is induced.

Ribulose-5-phosphate-3-epimerase (rpe) catalyzes the interconversion of D-ribulose-5-phosphate and xylulose-5-phosphate. Transketolase catalyzes the reversible transfer of a ketol group between several donor and acceptor substrates.

This enzyme is a reversible link between glycolysis and the pentose phosphate pathway. The enzyme is involved in the catabolism of pentose sugars, the formation of D-ribose 5-phosphate, and the provision of D-erythrose 4-phosphate. There are two transketolase enzymes in E. coli, catalyzed by tktA and tktB. Transketolase leads to the reversible conversion of erythrose-4-phosphate and xylulose-5-phosphate to form fructose-6-phosphate and glyceraldehyde-3-phosphate. Yet another reaction catalyzed by the enzyme is the interconversion of sedoheptulose-7-phosphate and glyceraldehyde-3-phosphate to form ribose-5-phosphate and xylulose-5-phosphate.

Transaldolase is another enzyme that forms a reversible link between the pentose phosphate pathway and glycolysis. It catalyzes the interconversion of glyceraldehyde-3-phosphate and sedoheptulose-7-phosphate to fructose-6-phosphate and erythrose-4-phosphate. There are two closely related transaldolases in E. coli, encoded by talA and talB. Homologues of these genes can be found in other microbes including C. glutamicum, S. cerevisiae, Pseudomonas putida, Bacillus subtilis. For sufficient flux to be carried through phosphoketolase, it is important to ensure that the flux capacity of the non-oxidative PP enzymes in not limiting.

When glucose is used as the carbon substrate the carbon flux distribution through the PTS and the Non-PTS system as well as the phosphoketolase can be modified to enhance bioderived product production. If Non-PTS system is not used, some flux will have to be diverted from pyruvate into oxaloacetate. This can be done by enzymes such as PEP synthetase in combination with phoshoenolpyruvate carboxylase or phoshoenolpyruvate carboxykinase, or by pyruvate carboxylase.

In some embodiments, the disclosure provides a non-naturally occurring microbial organism having an acetyl-CoA pathway, or oxaloacetate and acetyl-CoA pathway comprising phosphoketolase, and one or more of the following: (i) a non-PTS for sugar uptake comprising one or more genetic modification(s) to increase non-PTS activity, and/or (ii) one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP, to enhance synthesis or availability of reducing equivalents, or both, wherein the microbial organism further includes attenuation of one or more endogenous enzymes, which enhances carbon flux through acetyl-CoA into the product.

In some embodiments, the disclosure provides a non-naturally occurring microbial organism as having an acetyl-CoA pathway, or oxaloacetate and acetyl-CoA pathway comprising phosphoketolase, and/or, (ii) one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance synthesis or availability of reducing equivalents, or both, wherein the microbial organism further includes attenuation of one or more endogenous enzymes of a competing formaldehyde assimilation or dissimilation pathway. Examples of these endogenous enzymes are disclosed in FIG. 1 and described in Example XIII. It is understood that a person skilled in the art would be able to readily identify enzymes of such competing pathways. Competing pathways can be dependent upon the host microbial organism and/or the exogenous nucleic acid introduced into the microbial organism as described herein. Accordingly, in some aspects of the disclosure, the microbial organism includes attenuation of one, two, three, four, five, six, seven, eight, nine, ten or more endogenous enzymes of a competing formaldehyde assimilation or dissimilation pathway.

For example, in some aspects, the endogenous enzyme can be selected from DHA kinase, methanol oxidase, PQQ-dependent methanol dehydrogenase, DHA synthase or any combination thereof. Accordingly, in some aspects, the attenuation is of the endogenous enzyme DHA kinase. In some aspects, the attenuation is of the endogenous enzyme methanol oxidase. In some aspects, the attenuation is of the endogenous enzyme PQQ-dependent methanol dehydrogenase. In some aspects, the attenuation is of the endogenous enzyme DHA synthase. The invention also provides a microbial organism wherein attenuation is of any combination of two or three endogenous enzymes described herein. For example, a microbial organism of the invention can include attenuation of DHA kinase and DHA synthase, or alternatively methanol oxidase and PQQ-dependent methanol dehydrogenase, or alternatively DHA kinase, methanol oxidase, and PQQ-dependent methanol dehydrogenase, or alternatively DHA kinase, methanol oxidase, and DHA synthase. The invention also provides a microbial organism wherein attenuation is of all endogenous enzymes described herein. For example, in some aspects, a microbial organism described herein includes attenuation of DHA kinase, methanol oxidase, PQQ-dependent methanol dehydrogenase and DHA synthase. Competing pathways can be dependent upon the host microbial organism and/or the exogenous nucleic acid introduced into the microbial organism as described herein. Accordingly, in some aspects of the invention, the microbial organism includes a gene disruption of one, two, three, four, five, six, seven, eight, nine, ten or more endogenous nucleic acids encoding enzymes of a competing formaldehyde assimilation or dissimilation pathway.

Also provided is a method of producing a non-naturally occurring microbial organisms having stable growth-coupled production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound. The method can include identifying in silico a set of metabolic modifications that increase production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound, for example, increase production during exponential growth; genetically modifying an organism to contain the set of metabolic modifications that increase production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound, and culturing the genetically modified organism. If desired, culturing can include adaptively evolving the genetically modified organism under conditions requiring production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound. The methods of the invention are applicable to bacterium, yeast and fungus as well as a variety of other cells and microorganism, as disclosed herein.

Thus, the invention provides a non-naturally occurring microbial organism comprising one or more gene disruptions that confer increased synthesis or production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound. In one embodiment, the one or more gene disruptions confer growth-coupled production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound, and can, for example, confer stable growth-coupled production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound. In another embodiment, the one or more gene disruptions can confer obligatory coupling of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound production to growth of the microbial organism. Such one or more gene disruptions reduce the activity of the respective one or more encoded enzymes.

The non-naturally occurring microbial organism can have one or more gene disruptions included in a gene encoding an enzyme or protein disclosed herein. As disclosed herein, the one or more gene disruptions can be a deletion. Such non-naturally occurring microbial organisms of the invention include bacteria, yeast, fungus, or any of a variety of other microorganisms applicable to fermentation processes, as disclosed herein.

Thus, the invention provides a non-naturally occurring microbial organism, comprising one or more gene disruptions, where the one or more gene disruptions occur in genes encoding proteins or enzymes where the one or more gene disruptions confer increased production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound. The production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound can be growth-coupled or not growth-coupled. In a particular embodiment, the production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound can be obligatorily coupled to growth of the organism, as disclosed herein.

The invention provides non naturally occurring microbial organisms having genetic alterations such as gene disruptions that increase production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound, for example, growth-coupled production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound. Product production can be, for example, obligatorily linked to the exponential growth phase of the microorganism by genetically altering the metabolic pathways of the cell, as disclosed herein. The genetic alterations can increase the production of the desired product or even make the desired product an obligatory product during the growth phase. Metabolic alterations or transformations that result in increased production and elevated levels of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound biosynthesis are exemplified herein. Each alteration corresponds to the requisite metabolic reaction that should be functionally disrupted. Functional disruption of all reactions within one or more of the pathways can result in the increased production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound by the engineered strain during the growth phase.

Each of these non-naturally occurring alterations result in increased production and an enhanced level of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound, for example, during the exponential growth phase of the microbial organism, compared to a strain that does not contain such metabolic alterations, under appropriate culture conditions. Appropriate conditions include, for example, those disclosed herein, including conditions such as particular carbon sources or reactant availabilities and/or adaptive evolution.

Given the teachings and guidance provided herein, those skilled in the art will understand that to introduce a metabolic alteration such as attenuation of an enzyme, it can be necessary to disrupt the catalytic activity of the one or more enzymes involved in the reaction. Alternatively, a metabolic alteration can include disrupting expression of a regulatory protein necessary for enzyme activity or maximal activity. Disruption can occur by a variety of methods including, for example, deletion of an encoding gene or incorporation of a genetic alteration in one or more of the encoding gene sequences. The encoding genes targeted for disruption can be one, some, or all of the genes encoding enzymes involved in the catalytic activity. For example, where a single enzyme is involved in a targeted catalytic activity, disruption can occur by a genetic alteration that reduces or eliminates the catalytic activity of the encoded gene product. Similarly, where the single enzyme is multimeric, including heteromeric, disruption can occur by a genetic alteration that reduces or destroys the function of one or all subunits of the encoded gene products. Destruction of activity can be accomplished by loss of the binding activity of one or more subunits required to form an active complex, by destruction of the catalytic subunit of the multimeric complex or by both. Other functions of multimeric protein association and activity also can be targeted in order to disrupt a metabolic reaction of the invention. Such other functions are well known to those skilled in the art. Similarly, a target enzyme activity can be reduced or eliminated by disrupting expression of a protein or enzyme that modifies and/or activates the target enzyme, for example, a molecule required to convert an apoenzyme to a holoenzyme. Further, some or all of the functions of a single polypeptide or multimeric complex can be disrupted according to the invention in order to reduce or abolish the catalytic activity of one or more enzymes involved in a reaction or metabolic modification of the invention. Similarly, some or all of enzymes involved in a reaction or metabolic modification of the invention can be disrupted so long as the targeted reaction is reduced or eliminated.

Given the teachings and guidance provided herein, those skilled in the art also will understand that an enzymatic reaction can be disrupted by reducing or eliminating reactions encoded by a common gene and/or by one or more orthologs of that gene exhibiting similar or substantially the same activity. Reduction of both the common gene and all orthologs can lead to complete abolishment of any catalytic activity of a targeted reaction. However, disruption of either the common gene or one or more orthologs can lead to a reduction in the catalytic activity of the targeted reaction sufficient to promote coupling of growth to product biosynthesis. Exemplified herein are both the common genes encoding catalytic activities for a variety of metabolic modifications as well as their orthologs. Those skilled in the art will understand that disruption of some or all of the genes encoding an enzyme(s) of a targeted metabolic reaction can be practiced in the methods of the invention and incorporated into the non-naturally occurring microbial organisms of the invention in order to achieve the increased production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound or growth-coupled product production.

Given the teachings and guidance provided herein, those skilled in the art also will understand that enzymatic activity or expression can be attenuated using well known methods. Reduction of the activity or amount of an enzyme can mimic complete disruption of a gene if the reduction causes activity of the enzyme to fall below a critical level that is normally required for a pathway to function. Reduction of enzymatic activity by various techniques rather than use of a gene disruption can be important for an organism's viability. Methods of reducing enzymatic activity that result in similar or identical effects of a gene disruption include, but are not limited to: reducing gene transcription or translation; destabilizing mRNA, protein or catalytic RNA; and mutating a gene that affects enzyme activity or kinetics (See, Sambrook et al., Molecular Cloning: A Laboratory Manual, Third Ed., Cold Spring Harbor Laboratory, New York (2001); and Ausubel et al., Current Protocols in Molecular Biology, John Wiley and Sons, Baltimore, Md. (1999). Natural or imposed regulatory controls can also accomplish enzyme attenuation including: promoter replacement (See, Wang et al., Mol. Biotechnol. 52(2):300-308 (2012)); loss or alteration of transcription factors (Dietrick et al., Annu. Rev. Biochem. 79:563-590 (2010); and Simicevic et al., Mol. Biosyst. 6(3):462-468 (2010)); introduction of inhibitory RNAs or peptides such as siRNA, antisense RNA, RNA or peptide/small-molecule binding aptamers, ribozymes, aptazymes and riboswitches (Wieland et al., Methods 56(3):351-357 (2012); O'Sullivan, Anal. Bioanal. Chem. 372(1):44-48 (2002); and Lee et al., Curr. Opin. Biotechnol. 14(5):505-511 (2003)); and addition of drugs or other chemicals that reduce or disrupt enzymatic activity such as an enzyme inhibitor, an antibiotic or a target-specific drug.

One skilled in the art will also understand and recognize that attenuation of an enzyme can be done at various levels. For example, at the gene level, a mutation causing a partial or complete null phenotype, such as a gene disruption, or a mutation causing epistatic genetic effects that mask the activity of a gene product (Miko, Nature Education 1(1) (2008)), can be used to attenuate an enzyme. At the gene expression level, methods for attenuation include: coupling transcription to an endogenous or exogenous inducer, such as isopropylthio-β-galactoside (IPTG), then adding low amounts of inducer or no inducer during the production phase (Donovan et al., J. Ind. Microbiol. 16(3):145-154 (1996); and Hansen et al., Curr. Microbiol. 36(6):341-347 (1998)); introducing or modifying a positive or a negative regulator of a gene; modify histone acetylation/deacetylation in a eukaryotic chromosomal region where a gene is integrated (Yang et al., Curr. Opin. Genet. Dev. 13(2):143-153 (2003) and Kurdistani et al., Nat. Rev. Mol. Cell Biol. 4(4):276-284 (2003)); introducing a transposition to disrupt a promoter or a regulatory gene (Bleykasten-Brosshans et al., C. R. Biol. 33(8-9):679-686 (2011); and McCue et al., PLoS Genet. 8(2):e1002474 (2012)); flipping the orientation of a transposable element or promoter region so as to modulate gene expression of an adjacent gene (Wang et al., Genetics 120(4):875-885 (1988); Hayes, Annu. Rev. Genet. 37:3-29 (2003); in a diploid organism, deleting one allele resulting in loss of heterozygosity (Daigaku et al., Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 600(1-2)177-183 (2006)); introducing nucleic acids that increase RNA degradation (Houseley et al., Cell, 136(4):763-776 (2009); or in bacteria, for example, introduction of a transfer-messenger RNA (tmRNA) tag, which can lead to RNA degradation and ribosomal stalling (Sunohara et al., RNA 10(3):378-386 (2004); and Sunohara et al., J. Biol. Chem. 279:15368-15375 (2004)). At the translational level, attenuation can include: introducing rare codons to limit translation (Angov, Biotechnol. J. 6(6):650-659 (2011)); introducing RNA interference molecules that block translation (Castel et al., Nat. Rev. Genet. 14(2):100-112 (2013); and Kawasaki et al., Curr. Opin. Mol. Ther. 7(2):125-131 (2005); modifying regions outside the coding sequence, such as introducing secondary structure into an untranslated region (UTR) to block translation or reduce efficiency of translation (Ringner et al., PLoS Comput. Biol. 1(7):e72 (2005)); adding RNAase sites for rapid transcript degradation (Pasquinelli, Nat. Rev. Genet. 13(4):271-282 (2012); and Arraiano et al., FEMS Microbiol. Rev. 34(5):883-932 (2010); introducing antisense RNA oligomers or antisense transcripts (Nashizawa et al., Front. Biosci. 17:938-958 (2012)); introducing RNA or peptide aptamers, ribozymes, aptazymes, riboswitches (Wieland et al., Methods 56(3):351-357 (2012); O'Sullivan, Anal. Bioanal. Chem. 372(1):44-48 (2002); and Lee et al., Curr. Opin. Biotechnol. 14(5):505-511 (2003)); or introducing translational regulatory elements involving RNA structure that can prevent or reduce translation that can be controlled by the presence or absence of small molecules (Araujo et al., Comparative and Functional Genomics, Article ID 475731, 8 pages (2012)). At the level of enzyme localization and/or longevity, enzyme attenuation can include: adding a degradation tag for faster protein turnover (Hochstrasser, Annual Rev. Genet. 30:405-439 (1996); and Yuan et al., PLoS One 8(4):e62529 (2013)); or adding a localization tag that results in the enzyme being secreted or localized to a subcellular compartment in a eukaryotic cell, where the enzyme would not be able to react with its normal substrate (Nakai et al. Genomics 14(4):897-911 (1992); and Russell et al., J. Bact. 189(21)7581-7585 (2007)). At the level of post-translational regulation, enzyme attenuation can include: increasing intracellular concentration of known inhibitors; or modifying post-translational modified sites (Mann et al., Nature Biotech. 21:255-261 (2003)). At the level of enzyme activity, enzyme attenuation can include: adding an endogenous or an exogenous inhibitor, such as an enzyme inhibitor, an antibiotic or a target-specific drug, to reduce enzyme activity; chelating a metal ion that is required for enzyme activity; or introducing a dominant negative mutation. The applicability of a technique for attenuation described above can depend upon whether a given host microbial organism is prokaryotic or eukaryotic, and it is understand that a determination of what is the appropriate technique for a given host can be readily made by one skilled in the art.

In some embodiments, microaerobic designs can be used based on the growth-coupled formation of the desired product. To examine this, production cones can be constructed for each strategy by first maximizing and, subsequently minimizing the product yields at different rates of biomass formation feasible in the network. If the rightmost boundary of all possible phenotypes of the mutant network is a single point, it implies that there is a unique optimum yield of the product at the maximum biomass formation rate possible in the network. In other cases, the rightmost boundary of the feasible phenotypes is a vertical line, indicating that at the point of maximum biomass the network can make any amount of the product in the calculated range, including the lowest amount at the bottommost point of the vertical line. Such designs are given a low priority.

The acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound production strategies identified herein can be disrupted to increase production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound. Accordingly, the invention also provides a non-naturally occurring microbial organism having metabolic modifications coupling acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound production to growth of the organism, where the metabolic modifications includes disruption of one or more genes selected from the genes encoding proteins and/or enzymes shown in the various tables disclosed herein.

Each of the strains can be supplemented with additional deletions if it is determined that the strain designs do not sufficiently increase the production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound and/or couple the formation of the product with biomass formation. Alternatively, some other enzymes not known to possess significant activity under the growth conditions can become active due to adaptive evolution or random mutagenesis. Such activities can also be knocked out. However, the genes disclosed herein allows the construction of strains exhibiting high-yield synthesis or production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound, including growth-coupled production of acetyl-CoA or both oxaloacetate and acetyl-CoA or a bioderived compound.

The invention is described herein with general reference to the metabolic reaction, reactant or product thereof, or with specific reference to one or more nucleic acids or genes encoding an enzyme associated with or catalyzing, or a protein associated with, the referenced metabolic reaction, reactant or product. Unless otherwise expressly stated herein, those skilled in the art will understand that reference to a reaction also constitutes reference to the reactants and products of the reaction. Similarly, unless otherwise expressly stated herein, reference to a reactant or product also references the reaction, and reference to any of these metabolic constituents also references the gene or genes encoding the enzymes that catalyze or proteins involved in the referenced reaction, reactant or product. Likewise, given the well-known fields of metabolic biochemistry, enzymology and genomics, reference herein to a gene or encoding nucleic acid also constitutes a reference to the corresponding encoded enzyme and the reaction it catalyzes or a protein associated with the reaction as well as the reactants and products of the reaction

Depending on the non-natural microorganism capable of producing acetyl-CoA and oxaloacetate having a pathway(s) comprising phosphoketolase and a non-phosphotransferase system (non-PTS) for sugar uptake comprising a genetic modification to a non-PTS component to increase non-PTS activity, and/or (ii) one or more modification(s) to the organism's electron transport chain to enhance efficiency of ATP production, to enhance availability of reducing equivalents, or both. the non-naturally occurring microbial organisms of the invention can include at least one exogenous modification of a nucleic acid(s) from the pathway comprising phosphoketolase, the non-PTS system, or the ETC system. The non-natural microorganism can also include one or more exogenously expressed nucleic acid(s) from a bioderived compound pathway

For example, acetyl-CoA and oxaloacetate biosynthesis can be established in a host deficient in a pathway enzyme or protein through exogenous expression of the corresponding encoding nucleic acid. In a host deficient in all enzymes or proteins of an acetyl-CoA and oxaloacetate pathway, exogenous expression of all enzyme or proteins in the pathway can be included, although it is understood that all enzymes or proteins of a pathway can be expressed even if the host contains at least one of the pathway enzymes or proteins. For example, exogenous expression of all enzymes or proteins in a pathway for production of acetyl-CoA or a bioderived compound or for methanol utilization can be included, such as methanol dehydrogenase (see, e.g., FIG. 1) a fructose-6-phosphate phosphoketolase and a phosphotransacetylase (see, e.g. FIG. 1), or a xylulose-5-phosphate phosphoketolase and a phosphotransacetylase (see, e.g. FIG. 1), or a methanol dehydrogenase, a 3-hexulose-6-phosphate synthase, a 6-phospho-3-hexuloisomerase, a fructose-6-phosphate phosphoketolase and a phosphotransacetylase (see, e.g. FIG. 1), or an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase (ketone reducing), a 3-hydroxybutyryl-CoA reductase (aldehyde forming), and a 3-hydroxybutyraldehyde reductase (see, e.g. FIG. 5), or a succinyl-CoA reductase (aldehyde forming), a 4-HB dehydrogenase, a 4-HB kinase, a phosphotrans-4-hydroxybutyrylase, a 4-hydroxybutyryl-CoA reductase (aldehyde forming), and a 1,4-butanediol dehydrogenase (see, e.g. FIG. 7), or a 3-oxoadipyl-CoA thiolase, a 3-oxoadipyl-CoA reductase, a 3-hydroxyadipyl-CoA dehydratase, a 5-carboxy-2-pentenoyl-CoA reductase, an adipyl-CoA reductase (aldehyde forming), and 6-aminocaproate transaminase (see, e.g. FIG. 8), or an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase (ketone reducing), a 3-hydroxybutyrl-CoA mutase, a 2-hydroxyisobutyryl-CoA dehydratase, and a methacrylyl-CoA synthetase (see, e.g. FIG. 10).

Given the teachings and guidance provided herein, those skilled in the art will understand that the number of encoding nucleic acids to introduce in an expressible form will, at least, parallel the pathway comprising phosphoketolase for acetyl-CoA and oxaloacetate production, the non-PTS system, and/or the ETC system pathway deficiencies of the selected host microbial organism. Therefore, a non-naturally occurring microbial organism of the invention can have one, two, three, four, five, six, seven, eight, nine, ten, eleven, or twelve up to all nucleic acids encoding the enzymes or proteins constituting a pathway(s) comprising phosphoketolase to acetyl-CoA and oxaloacetate, a non-PTS, or ETC component, pathway disclosed herein. In some embodiments, the non-naturally occurring microbial organisms also can include other genetic modifications that facilitate or optimize acetyl-CoA biosynthesis, sugar uptake through the PTS or non-PTS, or ETC function, or that confer other useful functions onto the host microbial organism. One such other functionality can include, for example, augmentation of the synthesis of one or more of the acetyl-CoA pathway precursors. Optionally, the organism can include augmentation of the synthesis of one or more of the bioderived compound pathway precursors such as Fald, H6P, DHA, G3P, malonyl-CoA, acetoacetyl-CoA, PEP, PYR and Succinyl-CoA.

In some embodiments, a host microbial organism is selected such that it produces the precursor of an acetyl-CoA and oxaloacetate, and optionally further, a bioderived compound pathway, either as a naturally produced molecule or as an engineered product that either provides de novo production of a desired precursor or increased production of a precursor naturally produced by the host microbial organism. For example, malonyl-CoA, acetoacetyl-CoA and pyruvate are produced naturally in a host organism such as E. coli. A host organism can be engineered to increase production of a precursor, as disclosed herein. In addition, a microbial organism that has been engineered to produce a desired precursor can be used as a host organism and further engineered to express enzymes or proteins of an acetyl-CoA and oxaloacetate, and optionally a bioderived compound pathway.

In some embodiments, a non-naturally occurring microbial organism of the invention is generated from a host that contains the enzymatic capability to synthesize acetyl-CoA and oxaloactetate. In this specific embodiment it can be useful to increase the synthesis or accumulation of acetyl-CoA and oxaloactetate pathway product to, for example, to enhance bioderived compound pathway reactions. In turn, an increase in acetyl-CoA and oxaloactetate can be useful for enhancing a desired bioderived compound production. Increased synthesis or accumulation can be accomplished by, for example, overexpression of nucleic acids encoding one or more of the pathway(s) comprising phosphoketolase to acetyl-CoA and oxaloactetate, the non-PTS, and/or the ETC system, enzymes or proteins. Overexpression of the enzyme or enzymes and/or protein or proteins of the pathway(s) comprising phoshoketolase, the non-PTS, and/or ETC system can occur, for example, through exogenous expression of the endogenous gene or genes, or through exogenous expression of the heterologous gene or genes. Therefore, naturally occurring organisms can be readily generated to be non-naturally occurring microbial organisms of the invention, for example, producing acetyl-CoA, through overexpression of one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, that is, up to all nucleic acids encoding acetyl-CoA pathway enzymes or proteins. In addition, a non-naturally occurring organism can be generated by mutagenesis of an endogenous gene that results in an increase in activity of an enzyme in one or more of the pathway(s) comprising phosphoketolase to acetyl-CoA and oxaloactetate, the non-PTS system, and/or ETC system.

In particularly useful embodiments, exogenous expression of the encoding nucleic acids is employed. Exogenous expression confers the ability to custom tailor the expression and/or regulatory elements to the host and application to achieve a desired expression level that is controlled by the user. However, endogenous expression also can be utilized in other embodiments such as by removing a negative regulatory effector or induction of the gene's promoter when linked to an inducible promoter or other regulatory element. Thus, an endogenous gene having a naturally occurring inducible promoter can be up-regulated by providing the appropriate inducing agent, or the regulatory region of an endogenous gene can be engineered to incorporate an inducible regulatory element, thereby allowing the regulation of increased expression of an endogenous gene at a desired time. Similarly, an inducible promoter can be included as a regulatory element for an exogenous gene introduced into a non-naturally occurring microbial organism.

It is understood that, in methods of the invention, any of the one or more exogenous nucleic acids can be introduced into a microbial organism to produce a non-naturally occurring microbial organism of the disclosure. The nucleic acids can be introduced so as to confer, for example, an acetyl-CoA pathway onto the microbial organism. Alternatively, encoding nucleic acids can be introduced to produce an intermediate microbial organism having the biosynthetic capability to catalyze some of the required reactions to confer acetyl-CoA biosynthetic capability. For example, a non-naturally occurring microbial organism having an acetyl-CoA pathway can comprise at least two exogenous nucleic acids encoding desired enzymes or proteins, such as the combination of a 3-hexulose-6-phosphate synthase and a fructose-6-phosphate phosphoketolase, or alternatively a xylulose-5-phosphate phosphoketolase and an acetyl-CoA transferase, or alternatively a fructose-6-phosphate phosphoketolase and a formate reductase, or alternatively a xylulose-5-phosphate phosphoketolase and a methanol dehydrogenase, and the like. Thus, it is understood that any combination of two or more enzymes or proteins of a biosynthetic pathway can be included in a non-naturally occurring microbial organism of the invention.

The organism can include an exogenous nucleic acid encoding an enzyme or protein of the pathway(s) to acetyl-CoA and oxaloactetate comprising phosphoketolase, and can include modification of one or more natural or exogenous nucleic acids encoding an enzyme or protein of the non-PTS, and/or of an ETC system. For example, in some embodiments one or more exogenous nucleic acid(s) encoding an enzyme or protein of the pathway(s) to acetyl-CoA and oxaloactetate comprising phosphoketolase is introduced into an organism along with one or more modifications to an organism that provide or modify a non-phosphotransferase system (non-PTS) for sugar uptake, wherein the modification increases non-PTS activity. For example, the non-PTS modification can be one where the non-PTS for sugar uptake is introduced into an organism that does not have a non-PTS, or an organism having an endogenous (naturally-occurring or native) non-PTS can be modified to increase the activity or expression of one or more natural enzymes or proteins of the non-PTS. Optionally, this organism can also include one or more genetic modification(s) that attenuates or eliminates a PTS activity.

In other embodiments, for example, one or more exogenous nucleic acid(s) encoding an enzyme or protein of the pathway(s) to acetyl-CoA and oxaloactetate comprising phosphoketolase is introduced into an organism along with one or more genetic modifications of an ETC component(s). For example, the genetic modification that can enhance efficiency of ATP production can be (i) attenuation or elimination of an NADH-dependent dehydrogenase (e.g., Ndh, WrbA or YhdH, YieF, YtfG, Qor, MdaB) that does not translocate protons, or (ii) attenuation or elimination of a first cytochrome oxidase (e.g., CydAB or AppBC or YgiN) that has a lower efficiency of proton translocation per pair of electrons as compared to a second cytochrome oxidase. Energetic efficiency of the cell is thus increased. In another approach, the genetic modification can also increase expression or activity of a native or heterologous Complex I enzyme or protein and of cytochrome oxidases, such as by attenuating arcA. In another approach, the genetic modification that enhances the availability or synthesis of a reducing equivalent, can be done by using a genetic modification to increase the expression or activity of a pyruvate dehydrogenase, a pyruvate formate lyase together with an NAD(P)H-generating formate dehydrogenase.

Similarly, it is understood that any combination of three or more enzymes or proteins of a biosynthetic pathway can be included in a non-naturally occurring microbial organism of the disclosure, for example, a methanol dehydrogenase, a fructose-6-phosphate aldolase, and a fructose-6-phosphate phosphoketolase, or alternatively a fructose-6-phosphate phosphoketolase and a 3-hydroxybutyraldehyde reductase, or alternatively a xylulose-5-phosphate phosphoketolase, a pyruvate formate lyase and a 4-hydroxybutyryl-CoA reductase (alcohol forming), or alternatively a fructose-6-phosphate aldolase, a phosphotransacetylase, and a 3-hydroxyisobutyrate dehydratase, and so forth, as desired, so long as the combination of enzymes and/or proteins of the desired biosynthetic pathway results in production of the corresponding desired product. Similarly, any combination of four, five, six, seven, eight, nine, ten, eleven, twelve or more enzymes or proteins of a biosynthetic pathway as disclosed herein can be included in a non-naturally occurring microbial organism of the invention, as desired, so long as the combination of enzymes and/or proteins of the desired biosynthetic pathway results in production of the corresponding desired product.

In addition to the biosynthesis of acetyl-CoA and oxaloacetate as described herein, the non-naturally occurring microbial organisms and methods of the invention also can be utilized in various combinations with each other and/or with other microbial organisms and methods well known in the art to achieve product biosynthesis by other routes. For example, a non-natural organism having pathway(s) to acetyl-CoA and oxaloacetate comprising phosphoketolase, and that includes a non-PTS system modification, or an ETC system modification can be used to produce acetyl-CoA and oxaloacetate, which in turn can be utilized by a second organism capable of utilizing acetyl-CoA and/or oxaloacetate as a precursor in a bioderived compound pathway for the production of a desired product.

For example, the acetyl-CoA and/or oxaloacetate can be added directly to another culture of the second organism or the original culture of the acetyl-CoA and/or oxaloacetate can be depleted of these microbial organisms by, for example, cell separation, and then subsequent addition of the second organism to the fermentation broth can be utilized to produce the final product without intermediate purification steps.

In other embodiments, the non-naturally occurring microbial organisms and methods of the invention can be assembled in a wide variety of subpathways to achieve biosynthesis of, for example, acetyl-CoA and oxaloacetate, or optionally any a bioderived compound that uses acetyl-CoA and oxaloacetate in a pathway. In these embodiments, biosynthetic pathways for a desired product of the disclosure can be segregated into different microbial organisms, and the different microbial organisms can be co-cultured to produce the final product. In such a biosynthetic scheme, the product of one microbial organism is the substrate for a second microbial organism until the final product is synthesized. For example, the biosynthesis of acetyl-CoA and oxaloacetate, and optionally any bioderived compound, can be accomplished by constructing a microbial organism that contains biosynthetic pathways for conversion of one pathway intermediate to another pathway intermediate or the product. Alternatively, acetyl-CoA and oxaloacetate, and optionally any bioderived compound also can be biosynthetically produced from microbial organisms through co-culture or co-fermentation using two organisms in the same vessel, where the first microbial organism produces an acetyl-CoA and oxaloacetate or a bioderived compound intermediate and the second microbial organism converts the intermediate, acetyl-CoA, or oxaloacetate to a bioderived compound.

Given the teachings and guidance provided herein, those skilled in the art will understand that a wide variety of combinations and permutations exist for the non-naturally occurring microbial organisms and methods of the invention together with other microbial organisms, with the co-culture of other non-naturally occurring microbial organisms having subpathways and with combinations of other chemical and/or biochemical procedures well known in the art to produce acetyl-CoA and oxaloacetate, and optionally, further, a bioderived compound.

Similarly, it is understood by those skilled in the art that a host organism can be selected based on desired characteristics for introduction of one or more gene disruptions to increase synthesis or production of acetyl-CoA and oxaloacetate, and optionally, further, a bioderived compound. Thus, it is understood that, if a genetic modification is to be introduced into a host organism to disrupt a gene, any homologs, orthologs or paralogs that catalyze similar, yet non-identical metabolic reactions can similarly be disrupted to ensure that a desired metabolic reaction is sufficiently disrupted. Because certain differences exist among metabolic networks between different organisms, those skilled in the art will understand that the actual genes disrupted in a given organism may differ between organisms. However, given the teachings and guidance provided herein, those skilled in the art also will understand that the methods of the invention can be applied to any suitable host microorganism to identify the cognate metabolic alterations needed to construct an organism in a species of interest that will increase acetyl-CoA and optionally, further, a bioderived compound biosynthesis. In a particular embodiment, the increased production couples biosynthesis of acetyl-CoA and oxaloacetate and a bioderived compound to growth of the organism, and can obligatorily couple production of acetyl-CoA and a bioderived compound to growth of the organism if desired and as disclosed herein.

The non-naturally occurring microbial organisms of the invention can be produced by introducing expressible nucleic acids encoding one or more of the enzymes or proteins participating in one or more of the acetyl-CoA, or acetyl-CoA and oxaloacetate pathway comprising a phosphoketolase, (ii) a modification to enhance the non-PTS for sugar uptake, and/or (iii) one or more modification(s) to the organism's electron transport chain (ETC) to enhance efficiency of ATP production, to enhance availability of reducing equivalents, or both, or a bioderived compound biosynthetic pathways. Depending on the host microbial organism chosen for biosynthesis, nucleic acids for some or all of these pathways or systems can be expressed. For example, if a chosen host is deficient in one or more enzymes or proteins for a desired biosynthetic pathway, then expressible nucleic acids for the deficient enzyme(s) or protein(s) are introduced into the host for subsequent exogenous expression. Alternatively, if the chosen host exhibits endogenous expression of some pathway genes, but is deficient in others, then an encoding nucleic acid is needed for the deficient enzyme(s) or protein(s) to achieve acetyl-CoA and oxaloacetate production, the PTS, the non-PTS, the ETC modification, or a bioderived compound biosynthesis. Thus, a non-naturally occurring microbial organism of the invention can be produced by introducing exogenous enzyme or protein activities to obtain a desired biosynthetic pathway or a desired biosynthetic pathway can be obtained by introducing one or more exogenous enzyme or protein activities that, together with one or more endogenous enzymes or proteins, produces a desired product such as acetyl-CoA or a bioderived compound.

Host microbial organisms can be selected from, and the non-naturally occurring microbial organisms generated in, for example, bacteria, yeast, fungus or any of a variety of other microorganisms applicable or suitable to fermentation processes. Exemplary bacteria include any species selected from the order Enterobacteriales, family Enterobacteriaceae, including the genera Escherichia and Klebsiella; the order Aeromonadales, family Succinivibrionaceae, including the genus Anaerobiospirillum; the order Pasteurellales, family Pasteurellaceae, including the genera Actinobacillus and Mannheimia; the order Rhizobiales, family Bradyrhizobiaceae, including the genus Rhizobium; the order Bacillales, family Bacillaceae, including the genus Bacillus; the order Actinomycetales, families Corynebacteriaceae and Streptomycetaceae, including the genus Corynebacterium and the genus Streptomyces, respectively; order Rhodospirillales, family Acetobacteraceae, including the genus Gluconobacter; the order Sphingomonadales, family Sphingomonadaceae, including the genus Zymomonas; the order Lactobacillales, families Lactobacillaceae and Streptococcaceae, including the genus Lactobacillus and the genus Lactococcus, respectively; the order Clostridiales, family Clostridiaceae, genus Clostridium; and the order Pseudomonadales, family Pseudomonadaceae, including the genus Pseudomonas. Non-limiting species of host bacteria include Escherichia coli, Klebsiella oxytoca, Anaerobiospirillum succiniciproducens, Actinobacillus succinogenes, Mannheimia succiniciproducens, Rhizobium etli, Bacillus subtilis, Corynebacterium glutamicum, Gluconobacter oxydans, Zymomonas mobilis, Lactococcus lactis, Lactobacillus plantarum, Streptomyces coelicolor, Clostridium acetobutylicum, Pseudomonas fluorescens, and Pseudomonas putida. Exemplary bacterial methylotrophs include, for example, Bacillus, Methylobacterium, Methyloversatilis, Methylococcus, Methylocystis and Hyphomicrobium.

Similarly, exemplary species of yeast or fungi species include any species selected from the order Saccharomycetales, family Saccaromycetaceae, including the genera Saccharomyces, Kluyveromyces and Pichia; the order Saccharomycetales, family Dipodascaceae, including the genus Yarrowia; the order Schizosaccharomycetales, family Schizosaccaromycetaceae, including the genus Schizosaccharomyces; the order Eurotiales, family Trichocomaceae, including the genus Aspergillus; and the order Mucorales, family Mucoraceae, including the genus Rhizopus. Non-limiting species of host yeast or fungi include Saccharomyces cerevisiae, Schizosaccharomyces pombe, Kluyveromyces lactis, Kluyveromyces marxianus, Aspergillus terreus, Aspergillus niger, Pichia pastoris, Rhizopus arrhizus, Rhizopus oryzae, Yarrowia lipolytica, and the like. E. coli and C. glutamicum are particularly useful host organisms since they are well characterized microbial organism suitable for genetic engineering. Other particularly useful host organisms include yeast such as Saccharomyces cerevisiae and yeasts or fungi selected from the genera Saccharomyces, Schizosaccharomyces, Schizochytrium, Rhodotorula, Thraustochytrium, Aspergillus, Kluyveromyces, Issatchenkia, Yarrowia, Candida, Pichia, Ogataea, Kuraishia, Hansenula and Komagataella. Useful host organisms include Saccharomyces cerevisiae, Schizosaccharomyces pombe, Hansenula polymorpha, Pichia methanolica, Candida boidinii, Kluyveromyces lactis, Kluyveromyces marxianus, Aspergillus terreus, Aspergillus niger, Pichia pastoris, Rhizopus arrhizus, Rhizopus oryzae, Yarrowia lipolytica, Issatchenkia orientalis and the like. It is understood that any suitable microbial host organism can be used to introduce metabolic and/or genetic modifications to produce a desired product.

As used herein, the terms “non-natural” and “non-naturally occurring” when used in reference to a microbial organism or microorganism of the invention are intended to mean that the microbial organism has at least one genetic alteration not normally found in a naturally occurring strain of the referenced species, including wild-type strains of the referenced species. Genetic alterations include, for example, modifications introducing expressible nucleic acids encoding metabolic polypeptides, other nucleic acid additions, nucleic acid deletions and/or other functional disruption of the microbial organism's genetic material. Such modifications include, for example, coding regions and functional fragments thereof, for heterologous, homologous or both heterologous and homologous polypeptides for the referenced species. Additional modifications include, for example, non-coding regulatory regions in which the modifications alter expression of a gene or operon. Exemplary metabolic polypeptides include enzymes or proteins within a pathway to acetyl-CoA, or both oxaloacetate and acetyl-CoA, or bioderived compound biosynthetic pathway.

A metabolic modification refers to a biochemical reaction that is altered from its naturally occurring state. Therefore, non-naturally occurring microorganisms can have genetic modifications to nucleic acids encoding metabolic polypeptides, or functional fragments thereof. Exemplary metabolic modifications are disclosed herein.

As used herein, the term “isolated” when used in reference to a microbial organism is intended to mean an organism that is substantially free of at least one component as the referenced microbial organism is found in nature. The term includes a microbial organism that is removed from some or all components as it is found in its natural environment. The term also includes a microbial organism that is removed from some or all components as the microbial organism is found in non-naturally occurring environments. Therefore, an isolated microbial organism is partly or completely separated from other substances as it is found in nature or as it is grown, stored or subsisted in non-naturally occurring environments. Specific examples of isolated microbial organisms include partially pure microbes, substantially pure microbes and microbes cultured in a medium that is non-naturally occurring.

As used herein, the terms “microbial,” “microbial organism” or “microorganism” are intended to mean any organism that exists as a microscopic cell that is included within the domains of archaea, bacteria or eukarya. Therefore, the term is intended to encompass prokaryotic or eukaryotic cells or organisms having a microscopic size and includes bacteria, archaea and eubacteria of all species as well as eukaryotic microorganisms such as yeast and fungi. The term also includes cell cultures of any species that can be cultured for the production of a biochemical. The terms “bacterial,” and “bacterial organism” microbial organism are intended to mean any organism that exists as a microscopic cell within the domain of bacteria.

As used herein, the term “CoA” or “coenzyme A” is intended to mean an organic cofactor or prosthetic group (nonprotein portion of an enzyme) whose presence is required for the activity of many enzymes (the apoenzyme) to form an active enzyme system. Coenzyme A functions in certain condensing enzymes, acts in acetyl or other acyl group transfer and in fatty acid synthesis and oxidation, pyruvate oxidation and in other acetylation.

As used herein, the term “substantially anaerobic” when used in reference to a culture or growth condition is intended to mean that the amount of oxygen is less than about 10% of saturation for dissolved oxygen in liquid media. The term also is intended to include sealed chambers of liquid or solid medium maintained with an atmosphere of less than about 1% oxygen.

“Exogenous” as it is used herein is intended to mean that the referenced molecule or the referenced activity is introduced into the host microbial organism. The molecule can be introduced, for example, by introduction of an encoding nucleic acid into the host genetic material such as by integration into a host chromosome or as non-chromosomal genetic material such as a plasmid. Therefore, the term as it is used in reference to expression of an encoding nucleic acid refers to introduction of the encoding nucleic acid in an expressible form into the microbial organism. Included is any nucleic acid encoding a polypeptide in which its regulatory region, e.g. promoter, terminator, enhancer, has been changed from it native sequence. For example, modifying a native gene by replacing its promoter with a weaker or stronger results in an exogenous nucleic acid (or gene) encoding the referenced polypeptide. When used in reference to a biosynthetic activity, the term refers to an activity that is introduced into the host reference organism. The biosynthetic activity can be achieved by modifying a regulatory region, e.g. promoter, terminator, enhancer, to produce the biosynthetic activity from a native gene. For example, modifying a native gene by replacing its promoter with a constitutive or inducible promoter results in an exogenous biosynthetic activity. The source can be, for example, a homologous or heterologous encoding nucleic acid that expresses the referenced activity following introduction into the host microbial organism. Therefore, the term “endogenous” refers to a referenced molecule or activity that is present in the host. Similarly, the term when used in reference to expression of an encoding nucleic acid refers to expression of an encoding nucleic acid contained within the microbial organism. The term “heterologous” refers to a molecule or activity derived from a source other than the referenced species whereas “homologous” refers to a molecule or activity derived from the host microbial organism. Accordingly, exogenous expression of an encoding nucleic acid of the invention can utilize either or both a heterologous or homologous encoding nucleic acid.

It is understood that when more than one exogenous nucleic acid is included in a microbial organism that the more than one exogenous nucleic acids refers to the referenced encoding nucleic acid or biosynthetic activity, as discussed above. It is further understood, as disclosed herein, that such more than one exogenous nucleic acids can be introduced into the host microbial organism on separate nucleic acid molecules, on polycistronic nucleic acid molecules, or a combination thereof, and still be considered as more than one exogenous nucleic acid. For example, as disclosed herein a microbial organism can be engineered to express two or more exogenous nucleic acids encoding a desired pathway enzyme or protein. In the case where two exogenous nucleic acids encoding a desired activity are introduced into a host microbial organism, it is understood that the two exogenous nucleic acids can be introduced as a single nucleic acid, for example, on a single plasmid, on separate plasmids, can be integrated into the host chromosome at a single site or multiple sites, and still be considered as two exogenous nucleic acids. Similarly, it is understood that more than two exogenous nucleic acids can be introduced into a host organism in any desired combination, for example, on a single plasmid, on separate plasmids, can be integrated into the host chromosome at a single site or multiple sites, and still be considered as two or more exogenous nucleic acids, for example three exogenous nucleic acids. Thus, the number of referenced exogenous nucleic acids or biosynthetic activities refers to the number of encoding nucleic acids or the number of biosynthetic activities, not the number of separate nucleic acids introduced into the host organism.

As used herein, the phrase “enhance carbon flux” is intended to mean to intensify, increase, or further improve the extent or flow of metabolic carbon through or to a desired pathway, pathway product, intermediate, or bioderived compound. The intensity, increase or improvement can be relative to a predetermined baseline of a pathway product, intermediate or bioderived compound. For example, an increased yield of acetyl-CoA can be achieved per mole of methanol with a phosphoketolase enzyme described herein (see, e.g., FIG. 1) than in the absence of a phosphoketolase enzyme. Since an increased yield of acetyl-CoA can be achieved, a higher yield of acetyl-CoA derived compounds, such as 1,3-butanediol, crotyl alcohol, butadiene, 3-buten-2-ol, 2,4-pentadienoate, 1,4-butanediol, adipate, 6-aminocaproate, caprolactam, hexamethylenediamine, fatty alcohols such hexanol, octanol and dodecanol, propylene, isoprene, isopropanol, butanol, methacrylic acid and 2-hydroxyisobutyric acid the invention, can also be achieved.

As used herein, the term “gene disruption,” or grammatical equivalents thereof, is intended to mean a genetic alteration that renders the encoded gene product inactive or attenuated. The genetic alteration can be, for example, deletion of the entire gene, deletion of a regulatory sequence required for transcription or translation, deletion of a portion of the gene which results in a truncated gene product, or by any of various mutation strategies that inactivate or attenuate the encoded gene product, for example, replacement of a gene's promoter with a weaker promoter, replacement or insertion of one or more amino acid of the encoded protein to reduce its activity, stability or concentration, or inactivation of a gene's transactivating factor such as a regulatory protein. One particularly useful method of gene disruption is complete gene deletion because it reduces or eliminates the occurrence of genetic reversions in the non-naturally occurring microorganisms of the invention. A gene disruption also includes a null mutation, which refers to a mutation within a gene or a region containing a gene that results in the gene not being transcribed into RNA and/or translated into a functional gene product. Such a null mutation can arise from many types of mutations including, for example, inactivating point mutations, deletion of a portion of a gene, entire gene deletions, or deletion of chromosomal segments.

As used herein, the term “growth-coupled” when used in reference to the production of a biochemical product is intended to mean that the biosynthesis of the referenced biochemical product is produced during the growth phase of a microorganism. In a particular embodiment, the growth-coupled production can be obligatory, meaning that the biosynthesis of the referenced biochemical is an obligatory product produced during the growth phase of a microorganism.

As used herein, the term “attenuate,” or grammatical equivalents thereof, is intended to mean to weaken, reduce or diminish the activity or amount of an enzyme or protein compared to the activity of the naturally occurring enzyme which may be zero because it is not present. Attenuation of the activity or amount of an enzyme or protein can mimic complete disruption if the attenuation causes the activity or amount to fall below a critical level required for a given pathway to function. However, the attenuation of the activity or amount of an enzyme or protein that mimics complete disruption for one pathway, can still be sufficient for a separate pathway to continue to function. For example, attenuation of an endogenous enzyme or protein can be sufficient to mimic the complete disruption of the same enzyme or protein for production of acetyl-CoA or a bioderived compound of the invention, but the remaining activity or amount of enzyme or protein can still be sufficient to maintain other pathways, such as a pathway that is critical for the host microbial organism to survive, reproduce or grow. Attenuation of an enzyme or protein can also be weakening, reducing or diminishing the activity or amount of the enzyme or protein in an amount that is sufficient to increase yield of acetyl-CoA or a bioderived compound of the invention, but does not necessarily mimic complete disruption of the enzyme or protein. As used herein, the term “eliminated,” when referring to an enzyme or protein (or other molecule) or its activity, means the enzyme or protein or its activity is not present in the cell. Expression of an enzyme or protein can be eliminated when the nucleic acid that normally encodes the enzyme or protein, is not expressed.

Comparatively, if an enzyme or protein (or other molecule), such as one in a modified form, exhibits activity greater than the activity of its wild-type form, its activity is referred to as “enhanced” or “increased.” This includes a modification where there was an absence in the host organism of the enzyme, protein, other molecule or activity to be enhanced or increased. For example, the inclusion and expression of an exogenous or heterologous nucleic acid in a host that otherwise in a wild-type form does not have the nucleic acid can be referred to as “enhanced” or “increased.” Likewise, if an enzyme is expressed in a non-natural cell in an amount greater than the amount expressed in the natural (unmodified) cell (including where the enzyme is absent in the starting cell), its expression is referred to as “enhanced” or “upregulated.”

As used herein, the term “bioderived” means derived from or synthesized by a biological organism and can be considered a renewable resource since it can be generated by a biological organism. Such a biological organism, in particular the microbial organisms of the invention, can utilize a variety of carbon sources described herein including feedstock or biomass, such as, sugars and carbohydrates obtained from an agricultural, plant, bacterial, or animal source. Alternatively, the biological organism can utilize, for example, atmospheric carbon and/or methanol as a carbon source.

As used herein, the term “biobased” means a product as described herein that is composed, in whole or in part, of a bioderived compound of the invention. A biobased product is in contrast to a petroleum based product, wherein such a product is derived from or synthesized from petroleum or a petrochemical feedstock.

A “bioderived compound,” as used herein, refers to a target molecule or chemical that is derived from or synthesized by a biological organism. In the context of the present invention, engineered microbial organisms are used to produce a bioderived compound or intermediate thereof via acetyl-CoA, including optionally further through acetoacetyl-CoA, malonyl-CoA and/or succinyl-CoA. Bioderived compounds of the invention include, but are not limited to, alcohols, glycols, organic acids, alkenes, dienes, organic amines, organic aldehydes, vitamins, nutraceuticals and pharmaceuticals.

The non-naturally occurring microbial organisms of the invention can contain stable genetic alterations, which refers to microorganisms that can be cultured for greater than five generations without loss of the alteration. Generally, stable genetic alterations include modifications that persist greater than 10 generations, particularly stable modifications will persist more than about 25 generations, and more particularly, stable genetic modifications will be greater than 50 generations, including indefinitely.

In the case of gene disruptions, a particularly useful stable genetic alteration is a gene deletion. The use of a gene deletion to introduce a stable genetic alteration is particularly useful to reduce the likelihood of a reversion to a phenotype prior to the genetic alteration. For example, stable growth-coupled production of a biochemical can be achieved, for example, by deletion of a gene encoding an enzyme catalyzing one or more reactions within a set of metabolic modifications. For example, a non-natural organism of the current disclosure can include a gene deletion of pyruvate kinase, a gene deletion of an enzyme or protein of the PTS, such as deletion of ptsI, a deletion of a cytochrome oxidase that has a lower efficiency of proton translocation per pair of electrons, such as deletion of CydAB or AppBC or YgiN, or deletion of a NADH-dependent dehydrogenase that does not translocate protons, such as deletion of Ndh, WrbA, YhdH, YieF, YtfG, Qor, MdaB, or combinations thereof. The stability of growth-coupled production of a biochemical can be further enhanced through multiple deletions, significantly reducing the likelihood of multiple compensatory reversions occurring for each disrupted activity.

Those skilled in the art will understand that the genetic alterations, including metabolic modifications exemplified herein, are described with reference to a suitable host organism such as E. coli and their corresponding metabolic reactions or a suitable source organism for desired genetic material such as genes for a desired metabolic pathway. However, given the complete genome sequencing of a wide variety of organisms and the high level of skill in the area of genomics, those skilled in the art will readily be able to apply the teachings and guidance provided herein to essentially all other organisms. For example, the E. coli metabolic alterations exemplified herein can readily be applied to other species by incorporating the same or analogous encoding nucleic acid from species other than the referenced species. Such genetic alterations include, for example, genetic alterations of species homologs, in general, and in particular, orthologs, paralogs or nonorthologous gene displacements.

An ortholog is a gene or genes that are related by vertical descent and are responsible for substantially the same or identical functions in different organisms. For example, mouse epoxide hydrolase and human epoxide hydrolase can be considered orthologs for the biological function of hydrolysis of epoxides. Genes are related by vertical descent when, for example, they share sequence similarity of sufficient amount to indicate they are homologous, or related by evolution from a common ancestor. Genes can also be considered orthologs if they share three-dimensional structure but not necessarily sequence similarity, of a sufficient amount to indicate that they have evolved from a common ancestor to the extent that the primary sequence similarity is not identifiable. Genes that are orthologous can encode proteins with sequence similarity of about 25% to 100% amino acid sequence identity. Genes encoding proteins sharing an amino acid similarity less than 25% can also be considered to have arisen by vertical descent if their three-dimensional structure also shows similarities. Members of the serine protease family of enzymes, including tissue plasminogen activator and elastase, are considered to have arisen by vertical descent from a common ancestor.

Orthologs include genes or their encoded gene products that through, for example, evolution, have diverged in structure or overall activity. For example, where one species encodes a gene product exhibiting two functions and where such functions have been separated into distinct genes in a second species, the three genes and their corresponding products are considered to be orthologs. For the production of a biochemical product, those skilled in the art will understand that the orthologous gene harboring the metabolic activity to be introduced or disrupted is to be chosen for construction of the non-naturally occurring microorganism. An example of orthologs exhibiting separable activities is where distinct activities have been separated into distinct gene products between two or more species or within a single species. A specific example is the separation of elastase proteolysis and plasminogen proteolysis, two types of serine protease activity, into distinct molecules as plasminogen activator and elastase. A second example is the separation of mycoplasma 5′-3′ exonuclease and Drosophila DNA polymerase III activity. The DNA polymerase from the first species can be considered an ortholog to either or both of the exonuclease or the polymerase from the second species and vice versa.

In contrast, paralogs are homologs related by, for example, duplication followed by evolutionary divergence and have similar or common, but not identical functions. Paralogs can originate or derive from, for example, the same species or from a different species. For example, microsomal epoxide hydrolase (epoxide hydrolase I) and soluble epoxide hydrolase (epoxide hydrolase II) can be considered paralogs because they represent two distinct enzymes, co-evolved from a common ancestor, that catalyze distinct reactions and have distinct functions in the same species. Paralogs are proteins from the same species with significant sequence similarity to each other suggesting that they are homologous, or related through co-evolution from a common ancestor. Groups of paralogous protein families include HipA homologs, luciferase genes, peptidases, and others.

A nonorthologous gene displacement is a nonorthologous gene from one species that can substitute for a referenced gene function in a different species. Substitution includes, for example, being able to perform substantially the same or a similar function in the species of origin compared to the referenced function in the different species. Although generally, a nonorthologous gene displacement will be identifiable as structurally related to a known gene encoding the referenced function, less structurally related but functionally similar genes and their corresponding gene products nevertheless will still fall within the meaning of the term as it is used herein. Functional similarity requires, for example, at least some structural similarity in the active site or binding region of a nonorthologous gene product compared to a gene encoding the function sought to be substituted. Therefore, a nonorthologous gene includes, for example, a paralog or an unrelated gene.

Therefore, in identifying and constructing the non-naturally occurring microbial organisms of the invention having acetyl-CoA or a bioderived compound biosynthetic capability, those skilled in the art will understand with applying the teaching and guidance provided herein to a particular species that the identification of metabolic modifications can include identification and inclusion or inactivation of orthologs. To the extent that paralogs and/or nonorthologous gene displacements are present in the referenced microorganism that encode an enzyme catalyzing a similar or substantially similar metabolic reaction, those skilled in the art also can utilize these evolutionally related genes. Similarly for a gene disruption, evolutionally related genes can also be disrupted or deleted in a host microbial organism to reduce or eliminate functional redundancy of enzymatic activities targeted for disruption.

Orthologs, paralogs and nonorthologous gene displacements can be determined by methods well known to those skilled in the art. For example, inspection of nucleic acid or amino acid sequences for two polypeptides will reveal sequence identity and similarities between the compared sequences. Based on such similarities, one skilled in the art can determine if the similarity is sufficiently high to indicate the proteins are related through evolution from a common ancestor. Algorithms well known to those skilled in the art, such as Align, BLAST, Clustal W and others compare and determine a raw sequence similarity or identity, and also determine the presence or significance of gaps in the sequence which can be assigned a weight or score. Such algorithms also are known in the art and are similarly applicable for determining nucleotide sequence similarity or identity. Parameters for sufficient similarity to determine relatedness are computed based on well-known methods for calculating statistical similarity, or the chance of finding a similar match in a random polypeptide, and the significance of the match determined. A computer comparison of two or more sequences can, if desired, also be optimized visually by those skilled in the art. Related gene products or proteins can be expected to have a high similarity, for example, 25% to 100% sequence identity. Proteins that are unrelated can have an identity which is essentially the same as would be expected to occur by chance, if a database of sufficient size is scanned (about 5%). Sequences between 5% and 24% may or may not represent sufficient homology to conclude that the compared sequences are related. Additional statistical analysis to determine the significance of such matches given the size of the data set can be carried out to determine the relevance of these sequences.

Exemplary parameters for determining relatedness of two or more sequences using the BLAST algorithm, for example, can be as set forth below. Briefly, amino acid sequence alignments can be performed using BLASTP version 2.0.8 (Jan. 5, 1999) and the following parameters: Matrix: 0 BLOSUM62; gap open: 11; gap extension: 1; x_dropoff: 50; expect: 10.0; wordsize: 3; filter: on. Nucleic acid sequence alignments can be performed using BLASTN version 2.0.6 (Sep. 16, 1998) and the following parameters: Match: 1; mismatch: −2; gap open: 5; gap extension: 2; x_dropoff: 50; expect: 10.0; wordsize: 11; filter: off Those skilled in the art will know what modifications can be made to the above parameters to either increase or decrease the stringency of the comparison, for example, and determine the relatedness of two or more sequences.

Alcohols of the invention, including biofuel alcohols, include primary alcohols, secondary alcohols, diols and triols, preferably having C3 to C10 carbon atoms. Alcohols include n-propanol and isopropanol. Biofuel alcohols are preferably C3-C10 and include 1-Propanol, Isopropanol, 1-Butanol, Isobutanol, 1-Pentanol, Isopentenol, 2-Methyl-1-butanol, 3-Methyl-1-butanol, 1-Hexanol, 3-Methyl-1-pentanol, 1-Heptanol, 4-Methyl-1-hexanol, and 5-Methyl-1-hexanol. Diols include propanediols and butanediols, including 1,4 butanediol, 1,3-butanediol and 2,3-butanediol. Fatty alcohols include C4-C27 fatty alcohols, including C12-C18, especially C12-C14, including saturate or unsaturated linear fatty alcohols.

Further exemplary bioderived compounds of the invention include: (a) 1,4-butanediol and intermediates thereto, such as 4-hydroxybutanoic acid (4-hydroxybutanoate, 4-hydroxybutyrate (4-HB); (b) butadiene (1,3-butadiene) and intermediates thereto, such as 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, crotyl alcohol, 3-buten-2-ol (methyl vinyl carbinol), 2,4-pentadienoate and 3-buten-1-ol; (c) 1,3-butanediol and intermediates thereto, such as 3-hydroxybutyrate (3-HB), 2,4-pentadienoate, crotyl alcohol or 3-buten-1-ol; (d) adipate, 6-aminocaproic acid (6-ACA), caprolactam, hexamethylenediamine (HMDA) and levulinic acid and their intermediates, e.g. adipyl-CoA, 4-aminobutyryl-CoA; (e) methacrylic acid (2-methyl-2-propenoic acid) and its esters, such as methyl methacrylate and methyl methacrylate (known collectively as methacrylates), 3-hydroxyisobutyrate and/or 2-hydroxyisobutyrate and their intermediates; (f) glycols, including 1,2-propanediol (propylene glycol), 1,3-propanediol, glycerol, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol and bisphenol A and their intermediates; (g) other olefins including propylene and isoprenoids, (h) succinic acid and intermediates thereto; and (i) fatty alcohols, which are aliphatic compounds containing one or more hydroxyl groups and a chain of 4 or more carbon atoms, or fatty acids and fatty aldehydes thereof, which are preferably C4-C27 carbon atoms. Fatty alcohols include saturated fatty alcohols, unsaturated fatty alcohols and linear saturated fatty alcohols. Examples fatty alcohols include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl alcohols, and their corresponding oxidized derivatives, i.e. fatty aldehydes or fatty acids having the same number of carbon atoms. Preferred fatty alcohols, fatty aldehydes and fatty acids have C8 to C18 carbon atoms, especially C12-C18, C12-C14, and C16-C18, including C12, C13, C14, C15, C16, C17, and C18 carbon atoms. Preferred fatty alcohols include linear unsaturated fatty alcohols, such as dodecanol (C12; lauryl alcohol), tridecyl alcohol (C13; 1-tridecanol, tridecanol, isotridecanol), myristyl alcohol (C14; 1-tetradecanol), pentadecyl alcohol (C15; 1-pentadecanol, pentadecanol), cetyl alcohol (C16; 1-hexadecanol), heptadecyl alcohol (C17; 1-n-heptadecanol, heptadecanol) and stearyl alcohol (C18; 1-octadecanol) and unsaturated counterparts including palmitoleyl alcohol (C16 unsaturated; cis-9-hexadecen-1-ol), or their corresponding fatty aldehydes or fatty acids.

1,4-Butanediol and intermediates thereto, such as 4-hydroxybutanoic acid (4-hydroxybutanoate, 4-hydroxybutyrate, 4-HB), are bioderived compounds that can be made via enzymatic pathways described herein and in the following publications. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: WO2008115840A2 published 25 Sep. 2008 entitled Compositions and Methods for the Biosynthesis of 1,4-Butanediol and Its Precursors; WO2010141780A1 published 9 Dec. 2010 entitled Process of Separating Components of A Fermentation Broth; WO2010141920A2 published 9 Dec. 2010 entitled Microorganisms for the Production of 1,4-Butanediol and Related Methods; WO2010030711A2 published 18 Mar. 2010 entitled Microorganisms for the Production of 1,4-Butanediol; WO2010071697A1 published 24 Jun. 2010 Microorganisms and Methods for Conversion of Syngas and Other Carbon Sources to Useful Products; WO2009094485A1 published 30 Jul. 2009 Methods and Organisms for Utilizing Synthesis Gas or Other Gaseous Carbon Sources and Methanol; WO2009023493A1 published 19 Feb. 2009 entitled Methods and Organisms for the Growth-Coupled Production of 1,4-Butanediol; and WO2008115840A2 published 25 Sep. 2008 entitled Compositions and Methods for the Biosynthesis of 1,4-Butanediol and Its Precursors, which are all incorporated herein by reference.

Butadiene and intermediates thereto, such as 1,4-butanediol, 2,3-butanediol, 1,3-butanediol, crotyl alcohol, 3-buten-2-ol (methyl vinyl carbinol) and 3-buten-1-ol, are bioderived compounds that can be made via enzymatic pathways described herein and in the following publications. In addition to direct fermentation to produce butadiene, 1,3-butanediol, 1,4-butanediol, crotyl alcohol, 3-buten-2-ol (methyl vinyl carbinol) or 3-buten-1-ol can be separated, purified (for any use), and then chemically dehydrated to butadiene by metal-based catalysis. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: WO2011140171A2 published 10 Nov. 2011 entitled Microorganisms and Methods for the Biosynthesis of Butadiene; WO2012018624A2 published 9 Feb. 2012 entitled Microorganisms and Methods for the Biosynthesis of Aromatics, 2,4-Pentadienoate and 1,3-Butadiene; WO2011140171A2 published 10 Nov. 2011 entitled Microorganisms and Methods for the Biosynthesis of Butadiene; WO2013040383A1 published 21 Mar. 2013 entitled Microorganisms and Methods for Producing Alkenes; WO2012177710A1 published 27 Dec. 2012 entitled Microorganisms for Producing Butadiene and Methods Related thereto; WO2012106516A1 published 9 Aug. 2012 entitled Microorganisms and Methods for the Biosynthesis of Butadiene; and WO2013028519A1 published 28 Feb. 2013 entitled Microorganisms and Methods for Producing 2,4-Pentadienoate, Butadiene, Propylene, 1,3-Butanediol and Related Alcohols, which are all incorporated herein by reference.

1,3-Butanediol and intermediates thereto, such as 2,4-pentadienoate, crotyl alcohol or 3-buten-1-ol, are bioderived compounds that can be made via enzymatic pathways described herein and in the following publications. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: WO2011071682A1 published 16 Jun. 2011 entitled Methods and Organisms for Converting Synthesis Gas or Other Gaseous Carbon Sources and Methanol to 1,3-Butanediol; WO2011031897A published 17 Mar. 2011 entitled Microorganisms and Methods for the Co-Production of Isopropanol with Primary Alcohols, Diols and Acids; WO2010127319A2 published 4 Nov. 2010 entitled Organisms for the Production of 1,3-Butanediol; WO2013071226A1 published 16 May 2013 entitled Eukaryotic Organisms and Methods for Increasing the Availability of Cytosolic Acetyl-CoA, and for Producing 1,3-Butanediol; WO2013028519A1 published 28 Feb. 2013 entitled Microorganisms and Methods for Producing 2,4-Pentadienoate, Butadiene, Propylene, 1,3-Butanediol and Related Alcohols; WO2013036764A1 published 14 Mar. 2013 entitled Eukaryotic Organisms and Methods for Producing 1,3-Butanediol; WO2013012975A1 published 24 Jan. 2013 entitled Methods for Increasing Product Yields; and WO2012177619A2 published 27 Dec. 2012 entitled Microorganisms for Producing 1,3-Butanediol and Methods Related Thereto, which are all incorporated herein by reference.

Adipate, 6-aminocaproic acid, caprolactam, hexamethylenediamine and levulinic acid, and their intermediates, e.g. 4-aminobutyryl-CoA, are bioderived compounds that can be made via enzymatic pathways described herein and in the following publications. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: WO2010129936A1 published 11 Nov. 2010 entitled Microorganisms and Methods for the Biosynthesis of Adipate, Hexamethylenediamine and 6-Aminocaproic Acid; WO2013012975A1 published 24 Jan. 2013 entitled Methods for Increasing Product Yields; WO2012177721A1 published 27 Dec. 2012 entitled Microorganisms for Producing 6-Aminocaproic Acid; WO2012099621A1 published 26 Jul. 2012 entitled Methods for Increasing Product Yields; and WO2009151728 published 17 Dec. 2009 entitled Microorganisms for the production of adipic acid and other compounds, which are all incorporated herein by reference.

Methacrylic acid (2-methyl-2-propenoic acid) is used in the preparation of its esters, known collectively as methacrylates (e.g. methyl methacrylate, which is used most notably in the manufacture of polymers). Methacrylate esters such as methyl methacrylate, 3-hydroxyisobutyrate and/or 2-hydroxyisobutyrate and their intermediates are bioderived compounds that can be made via enzymatic pathways described herein and in the following publications. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: WO2012135789A2 published 4 Oct. 2012 entitled Microorganisms for Producing Methacrylic Acid and Methacrylate Esters and Methods Related Thereto; and WO2009135074A2 published 5 Nov. 2009 entitled Microorganisms for the Production of Methacrylic Acid, which are all incorporated herein by reference.

1,2-Propanediol (propylene glycol), n-propanol, 1,3-propanediol and glycerol, and their intermediates are bioderived compounds that can be made via enzymatic pathways described herein and in the following publications. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: WO2009111672A1 published 9 Nov. 2009 entitled Primary Alcohol Producing Organisms; WO2011031897A1 17 Mar. 2011 entitled Microorganisms and Methods for the Co-Production of Isopropanol with Primary Alcohols, Diols and Acids; WO2012177599A2 published 27 Dec. 2012 entitled Microorganisms for Producing N-Propanol 1,3-Propanediol, 1,2-Propanediol or Glycerol and Methods Related Thereto, which are all incorporated herein by referenced.

Succinic acid and intermediates thereto, which are useful to produce products including polymers (e.g. PBS), 1,4-butanediol, tetrahydrofuran, pyrrolidone, solvents, paints, deicers, plastics, fuel additives, fabrics, carpets, pigments, and detergents, are bioderived compounds that can be made via enzymatic pathways described herein and in the following publication. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: EP1937821A2 published 2 Jul. 2008 entitled Methods and Organisms for the Growth-Coupled Production of Succinate, which is incorporated herein by reference.

Primary alcohols and fatty alcohols (also known as long chain alcohols), including fatty acids and fatty aldehydes thereof, and intermediates thereto, are bioderived compounds that can be made via enzymatic pathways in the following publications. Suitable bioderived compound pathways and enzymes, methods for screening and methods for isolating are found in: WO2009111672 published 11 Sep. 2009 entitled Primary Alcohol Producing Organisms; WO2012177726 published 27 Dec. 2012 entitled Microorganism for Producing Primary Alcohols and Related Compounds and Methods Related Thereto, which are all incorporated herein by reference.

Olefins includes an isoprenoid, which can be a bioderived product. Pathways and enzymes for producing an isoprenoid in a microbial organism and microbial organisms having those pathways and enzymes include those described in WO2013071172 entitled “Production of acetyl-coenzyme A derived isoprenoids”, WO2012154854 entitled “Production of acetyl-coenzyme A derived compounds”, WO2012016172 entitled “Genetically modified microbes producing increased levels of acetyl-CoA derived compounds”, WO2012016177 entitled “Genetically modified microbes producing increased levels of acetyl-CoA derived compounds”, WO2008128159 entitled “Production of isoprenoids” or U.S. Pat. No. 8,415,136 entitled “Production of acetyl-coenzyme A derived isoprenoids”, which are incorporated herein by reference. The isoprenoid can a hemiterpene, monoterpene, diterpene, triterpene, tetraterpene, sesquiterpene, and polyterpene. The isoprenoid is preferably a C5-C20 isoprenoid. The isoprenoid can be abietadiene, amorphadiene, carene, a-farnesene, β-farnesene, farnesol, geraniol, geranylgeraniol, isoprene, linalool, limonene, myrcene, nerolidol, ocimene, patchoulol, β-pinene, sabinene, γ-terpinene, terpinolene, and valencene. A particularly preferred isoprenoid is isoprene.

Further suitable bioderived compounds that the microbial organisms of the invention can be used to produce via acetyl-CoA, including optionally further through acetoacetyl-CoA and/or succinyl-CoA, are included in the invention. Exemplary well known bioderived compounds, their pathways and enzymes for production, methods for screening and methods for isolating are found in the following patents and publications: succinate (U.S. publication 2007/0111294, WO 2007/030830, WO 2013/003432), 3-hydroxypropionic acid (3-hydroxypropionate) (U.S. publication 2008/0199926, WO 2008/091627, U.S. publication 2010/0021978), 1,4-butanediol (U.S. Pat. No. 8,067,214, WO 2008/115840, U.S. Pat. No. 7,947,483, WO 2009/023493, U.S. Pat. No. 7,858,350, WO 2010/030711, U.S. publication 2011/0003355, WO 2010/141780, U.S. Pat. No. 8,129,169, WO 2010/141920, U.S. publication 2011/0201068, WO 2011/031897, U.S. Pat. No. 8,377,666, WO 2011/047101, U.S. publication 2011/0217742, WO 2011/066076, U.S. publication 2013/0034884, WO 2012/177943), 4-hydroxybutanoic acid (4-hydroxybutanoate, 4-hydroxybutyrate, 4-hydroxybutryate) (U.S. Pat. No. 8,067,214, WO 2008/115840, U.S. Pat. No. 7,947,483, WO 2009/023493, U.S. Pat. No. 7,858,350, WO 2010/030711, U.S. publication 2011/0003355, WO 2010/141780, U.S. Pat. No. 8,129,155, WO 2010/071697), γ-butyrolactone (U.S. Pat. No. 8,067,214, WO 2008/115840, U.S. Pat. No. 7,947,483, WO 2009/023493, U.S. Pat. No. 7,858,350, WO 2010/030711, U.S. publication 2011/0003355, WO 2010/141780, U.S. publication 2011/0217742, WO 2011/066076), 4-hydroxybutyryl-CoA (U.S. publication 2011/0003355, WO 2010/141780, U.S. publication 2013/0034884, WO 2012/177943), 4-hydroxybutanal (U.S. publication 2011/0003355, WO 2010/141780, U.S. publication 2013/0034884, WO 2012/177943), putrescine (U.S. publication 2011/0003355, WO 2010/141780, U.S. publication 2013/0034884, WO 2012/177943), Olefins (such as acrylic acid and acrylate ester) (U.S. Pat. No. 8,026,386, WO 2009/045637), acetyl-CoA (U.S. Pat. No. 8,323,950, WO 2009/094485), methyl tetrahydrofolate (U.S. Pat. No. 8,323,950, WO 2009/094485), ethanol (U.S. Pat. No. 8,129,155, WO 2010/071697), isopropanol (U.S. Pat. No. 8,129,155, WO 2010/071697, U.S. publication 2010/0323418, WO 2010/127303, U.S. publication 2011/0201068, WO 2011/031897), n-butanol (U.S. Pat. No. 8,129,155, WO 2010/071697), isobutanol (U.S. Pat. No. 8,129,155, WO 2010/071697), n-propanol (U.S. publication 2011/0201068, WO 2011/031897), methylacrylic acid (methylacrylate) (U.S. publication 2011/0201068, WO 2011/031897), primary alcohol (U.S. Pat. No. 7,977,084, WO 2009/111672, WO 2012/177726), long chain alcohol (U.S. Pat. No. 7,977,084, WO 2009/111672, WO 2012/177726), adipate (adipic acid) (U.S. Pat. No. 8,062,871, WO 2009/151728, U.S. Pat. No. 8,377,680, WO 2010/129936, WO 2012/177721), 6-aminocaproate (6-aminocaproic acid) (U.S. Pat. No. 8,062,871, WO 2009/151728, U.S. Pat. No. 8,377,680, WO 2010/129936, WO 2012/177721), caprolactam (U.S. Pat. No. 8,062,871, WO 2009/151728, U.S. Pat. No. 8,377,680, WO 2010/129936, WO 2012/177721), hexamethylenediamine (U.S. Pat. No. 8,377,680, WO 2010/129936, WO 2012/177721), levulinic acid (U.S. Pat. No. 8,377,680, WO 2010/129936), 2-hydroxyisobutyric acid (2-hydroxyisobutyrate) (U.S. Pat. No. 8,241,877, WO 2009/135074, U.S. publication 2013/0065279, WO 2012/135789), 3-hydroxyisobutyric acid (3-hydroxyisobutyrate) (U.S. Pat. No. 8,241,877, WO 2009/135074, U.S. publication 2013/0065279, WO 2012/135789), methacrylic acid (methacrylate) (U.S. Pat. No. 8,241,877, WO 2009/135074, U.S. publication 2013/0065279, WO 2012/135789), methacrylate ester (U.S. publication 2013/0065279, WO 2012/135789), fumarate (fumaric acid) (U.S. Pat. No. 8,129,154, WO 2009/155382), malate (malic acid) (U.S. Pat. No. 8,129,154, WO 2009/155382), acrylate (carboxylic acid) (U.S. Pat. No. 8,129,154, WO 2009/155382), methyl ethyl ketone (U.S. publication 2010/0184173, WO 2010/057022, U.S. Pat. No. 8,420,375, WO 2010/144746), 2-butanol (U.S. publication 2010/0184173, WO 2010/057022, U.S. Pat. No. 8,420,375, WO 2010/144746), 1,3-butanediol (U.S. publication 2010/0330635, WO 2010/127319, U.S. publication 2011/0201068, WO 2011/031897, U.S. Pat. No. 8,268,607, WO 2011/071682, U.S. publication 2013/0109064, WO 2013/028519, U.S. publication 2013/0066035, WO 2013/036764), cyclohexanone (U.S. publication 2011/0014668, WO 2010/132845), terephthalate (terephthalic acid) (U.S. publication 2011/0124911, WO 2011/017560, U.S. publication 2011/0207185, WO 2011/094131, U.S. publication 2012/0021478, WO 2012/018624), muconate (muconic acid) (U.S. publication 2011/0124911, WO 2011/017560), aniline (U.S. publication 2011/0097767, WO 2011/050326), p-toluate (p-toluic acid) (U.S. publication 2011/0207185, WO 2011/094131, U.S. publication 2012/0021478, WO 2012/018624), (2-hydroxy-3-methyl-4-oxobutoxy)phosphonate (U.S. publication 2011/0207185, WO 2011/094131, U.S. publication 2012/0021478, WO 2012/018624), ethylene glycol (U.S. publication 2011/0312049, WO 2011/130378, WO 2012/177983), propylene (U.S. publication 2011/0269204, WO 2011/137198, U.S. publication 2012/0329119, U.S. publication 2013/0109064, WO 2013/028519), butadiene (1,3-butadiene) (U.S. publication 2011/0300597, WO 2011/140171, U.S. publication 2012/0021478, WO 2012/018624, U.S. publication 2012/0225466, WO 2012/106516, U.S. publication 2013/0011891, WO 2012/177710, U.S. publication 2013/0109064, WO 2013/028519), toluene (U.S. publication 2012/0021478, WO 2012/018624), benzene (U.S. publication 2012/0021478, WO 2012/018624), (2-hydroxy-4-oxobutoxy)phosphonate (U.S. publication 2012/0021478, WO 2012/018624), benzoate (benzoic acid) (U.S. publication 2012/0021478, WO 2012/018624), styrene (U.S. publication 2012/0021478, WO 2012/018624), 2,4-pentadienoate (U.S. publication 2012/0021478, WO 2012/018624, U.S. publication 2013/0109064, WO 2013/028519), 3-butene-1-ol (U.S. publication 2012/0021478, WO 2012/018624, U.S. publication 2013/0109064, WO 2013/028519), 3-buten-2-ol (U.S. publication 2013/0109064, WO 2013/028519), 1,4-cyclohexanedimethanol (U.S. publication 2012/0156740, WO 2012/082978), crotyl alcohol (U.S. publication 2013/0011891, WO 2012/177710, U.S. publication 2013/0109064, WO 2013/028519), alkene (U.S. publication 2013/0122563, WO 2013/040383, US 2011/0196180), hydroxyacid (WO 2012/109176), ketoacid (WO 2012/109176), wax esters (WO 2007/136762) or caprolactone (U.S. publication 2013/0144029, WO 2013/067432) pathway. The patents and patent application publications listed above that disclose bioderived compound pathways are herein incorporated herein by reference.

Acetyl-CoA is the immediate precursor for the synthesis of bioderived compounds as shown in FIGS. 5-10. Phosphoketolase pathways make possible synthesis of acetyl-CoA without requiring decarboxylation of pyruvate (Bogorad et al, Nature, 2013, published online 29 Sep. 2013; United States Publication 2006-0040365), which thereby provides higher yields of bioderived compounds of the invention from carbohydrates and methanol than the yields attainable without phosphoketolase enzymes.

For example, synthesis of an exemplary fatty alcohol, dodecanol, from methanol-using methanol dehydrogenase (step A of FIG. 1), a formaldehyde assimilation pathway (steps B, C, D of FIG. 1) the pentose phosphate pathway, and glycolysis can provide a maximum theoretical yield of 0.0556 mole dodecanol/mole methanol.

18CH₄O+9O₂→C₁₂H₂₆O+23H₂O+6CO₂

However, if these pathways are combined with an acetyl CoA pathway comprising Phosphoketolase (e.g, steps T, U, V, W, X of FIG. 1), a maximum theoretical yield of 0.0833 mole dodecanol/mole methanol can be obtained (pathway calculations not removing any ATP for cell growth and maintenance requirements).

12CH₄O→C₁₂H₂₆O+11H₂O

ATP for energetic requirements can be synthesized, at the expense of lowering the maximum theoretical product yield, by oxidizing methanol to CO₂using several combinations of enzymes, glycolysis, the TCA cycle, the pentose phosphate pathway, and oxidative phosphorylation.

Similarly, synthesis of isopropanol from methanol using methanol dehydrogenase (step A of FIG. 1), a formaldehyde assimilation pathway (e.g., steps B, C, D of FIG. 1), the pentose phosphate pathway and glycolysis can provide a maximum theoretical yield of 0.1667 mole isopropanol/mole methanol.

6CH₄O+4.5O₂→C₃H₈O+8H₂O+3CO₂

However, if these pathways are applied in combination with an acetyl CoA pathway comprising Phosphoketolase (e.g., steps T, U, V, W, X of FIG. 1), a maximum theoretical yield of 0.250 mole isopropanol/mole methanol can be obtained.

4CH₄O+1.5O₂→C₃H₈O+4H₂O+CO₂

The overall pathway is ATP and redox positive enabling synthesis of both ATP and NAD(P)H from conversion of MeOH to isopropanol. Additional ATP can be synthesized, at the expense of lowering the maximum theoretical product yield, by oxidizing methanol to CO₂using several combinations of enzymes, glycolysis, the TCA cycle, the pentose phosphate pathway, and oxidative phosphorylation.

Employing one or more methanol metabolic enzymes as described herein, for example as shown in FIGS. 1 and 2, methanol can enter central metabolism in most production hosts by employing methanol dehydrogenase (FIG. 1, step A) along with a pathway for formaldehyde assimilation. One exemplary formaldehyde assimilation pathway that can utilize formaldehyde produced from the oxidation of methanol is shown in FIG. 1, which involves condensation of formaldehyde and D-ribulose-5-phosphate to form hexulose-6-phosphate (H6P) by hexulose-6-phosphate synthase (FIG. 1, step B). The enzyme can use Mg²⁺or Mn²⁺ for maximal activity, although other metal ions are useful, and even non-metal-ion-dependent mechanisms are contemplated. H6P is converted into fructose-6-phosphate by 6-phospho-3-hexuloisomerase (FIG. 1, step C). Another exemplary pathway that involves the detoxification and assimilation of formaldehyde produced from the oxidation of methanol proceeds through dihydroxyacetone. Dihydroxyacetone synthase (FIG. 1, step D) is a transketolase that first transfers a glycoaldehyde group from xylulose-5-phosphate to formaldehyde, resulting in the formation of dihydroxyacetone (DHA) and glyceraldehyde-3-phosphate (G3P), which is an intermediate in glycolysis. The DHA obtained from DHA synthase can be then further phosphorylated to form DHA phosphate by a DHA kinase. DHAP can be assimilated into glycolysis, e.g. via isomerization to G3P, and several other pathways. Alternatively, DHA and G3P can be converted by fructose-6-phosphate aldolase to form fructose-6-phosphate (F6P) (FIG. 1, step Z).

Synthesis of several other products from methanol using methanol dehydrogenase (step A of FIG. 1), a formaldehyde assimilation pathway (e.g., steps B, C, D of FIG. 1), the pentose phosphate pathway and glycolysis can provide the following maximum theoretical yield stoichiometries:

Product
CH4O
O2
NH3

Product
H2O
CO2

1,3-Butanediol
6.000
3.500
0.000
-->
1.000
7.000
2.000

Crotyl Alcohol
6.000
3.500
0.000
-->
1.000
8.000
2.000

3-Buten-2-ol
6.000
3.500
0.000
-->
1.000
8.000
2.000

Butadiene
6.000
3.500
0.000
-->
1.000
9.000
2.000

2-Hydroxyisobutyrate
6.000
4.500
0.000
-->
1.000
8.000
2.000

Methacrylate (via 2-hydroxyisobutyrate)
6.000
4.500
0.000
-->
1.000
9.000
2.000

3-Hydroxyisobutyrate (oxidative TCA cycle)
6.000
4.500
0.000
-->
1.000
8.000
2.000

Methacrylate (via 3-hydroxyisobutyrate)
6.000
4.500
0.000
-->
1.000
9.000
2.000

1,4-Butanediol (oxidative TCA cycle)
6.000
3.500
0.000
-->
1.000
9.000
2.000

Adipate (oxidative TCA cycle)
9.000
7.000
0.000
-->
1.000
13.000
3.000

6-Aminocaproate (oxidative TCA cycle)
9.000
6.000
1.000
-->
1.000
13.000
3.000

Caprolactam (via 6-aminocaproate)
9.000
6.000
1.000
-->
1.000
14.000
3.000

Hexamethylenediamine (oxidative TCA cycle)
9.000
5.000
2.000
-->
1.000
13.000
3.000

In the products marked “oxidative TCA cycle”, the maximum yield stoichiometries assume that the reductive TCA cycle enzymes (e.g., malate dehydrogenase, fumarase, fumarate reductase, and succinyl-CoA ligase) are not utilized for product formation. Exclusive use of the oxidative TCA cycle for product formation can be advantageous for succinyl-CoA derived products such as 3-hydroxyisobutyrate, 1,4-butanediol, adipate, 6-aminocaproate, and hexamethylenediamine because it enables all of the product pathway flux to originate from alpha-ketoglutarate dehydrogenase—an irreversible enzyme in vivo. Production of succinyl-CoA via the oxidative TCA branch uses both acetyl-CoA and oxaoloacetate as precursors.

However, if these pathways are applied in combination with an acetyl CoA pathway comprising Phosphoketolase (e.g., steps T, U, V, W, X of FIG. 1), an increased maximum theoretical yield on methanol can be obtained as shown below:

Product
CH4O
O2
NH3

Product
H2O
CO2

1,3-Butanediol
4.000
0.500
0.000
-->
1.000
3.000
0.000

Crotyl Alcohol
4.000
0.500
0.000
-->
1.000
4.000
0.000

3-Buten-2-ol
4.000
0.500
0.000
-->
1.000
4.000
0.000

Butadiene
4.000
0.500
0.000
-->
1.000
5.000
0.000

2-Hydroxyisobutyrate
4.000
1.500
0.000
-->
1.000
4.000
0.000

Methacrylate (via 2-hydroxyisobutyrate)
4.000
1.500
0.000
-->
1.000
5.000
0.000

3-Hydroxyisobutyrate (oxidative TCA cycle)
5.000
3.000
0.000
-->
1.000
6.000
1.000

Methacrylate (via 3-hydroxyisobutyrate)
5.000
3.000
0.000
-->
1.000
7.000
1.000

1,4-Butanediol (oxidative TCA cycle)
5.000
2.000
0.000
-->
1.000
5.000
1.000

Adipate (oxidative TCA cycle)
7.000
4.000
0.000
-->
1.000
9.000
1.000

6-Aminocaproate (oxidative TCA cycle)
7.000
3.000
1.000
-->
1.000
9.000
1.000

Caprolactam (via 6-aminocaproate)
7.000
3.000
1.000
-->
1.000
10.000
1.000

Hexamethylenediamine (oxidative TCA cycle)
7.000
2.000
2.000
-->
1.000
9.000
1.000

The theoretical yield of bioderived compounds of the invention from carbohydrates including but not limited to glucose, glycerol, sucrose, fructose, xylose, arabinose, and galactose, can also be enhanced by phosphoketolase enzymes. This is because phosphoketolase enzymes provide acetyl-CoA synthesis with 100% carbon conversion efficiency (e.g., 3 acetyl-CoA's per glucose, 2.5 acetyl-CoA's per xylose, 1.5 acetyl-CoA's per glycerol).

For example, synthesis of isopropanol from glucose in the absence of phosphoketolase enzymes can achieve a maximum theoretical isopropanol yield of 1.000 mole isopropanol/mole glucose.

C₆H₁₂O₆+1.5O₂→C₃H₈O+2H₂O+3CO₂

However, if enzyme steps T, U, V, W, X of FIG. 1 are applied in combination with glycolysis and the pentose phosphate pathway, the maximum theoretical yield can be increased to 1.333 mole isopropanol/mole glucose.

C₆H₁₂O₆→1.333C₃H₈O+0.667H₂O+2CO₂

In the absence of phosphoketolase activity, synthesis of several other products from a carbohydrate source (e.g., glucose) can provide the following maximum theoretical yield stoichiometries using glycolysis, pentose phosphate pathway, and TCA cycle reactions to build the pathway precursors.

Product
C6H12O6
O2
NH3

Product
H2O
CO2

1,3-Butanediol
1.000
0.500
0.000
→
1.000
1.000
2.000

Crotyl Alcohol
1.000
0.500
0.000
→
1.000
2.000
2.000

3-Buten-2-ol
1.000
0.500
0.000
→
1.000
2.000
2.000

Butadiene
1.000
0.500
0.000
→
1.000
3.000
2.000

2-Hydroxyisobutyrate
1.000
1.500
0.000
→
1.000
2.000
2.000

Methacrylate (via 2-hydroxyisobutyrate)
1.000
1.500
0.000
→
1.000
3.000
2.000

3-Hydroxyisobutyrate (oxidative TCA cycle)
1.000
1.500
0.000
→
1.000
2.000
2.000

Methacrylate (via 3-hydroxyisobutyrate)
1.000
1.500
0.000
→
1.000
3.000
2.000

1,4-Butanediol (oxidative TCA cycle)
1.000
0.500
0.000
→
1.000
1.000
2.000

Adipate (oxidative TCA cycle)
1.000
1.667
0.000
→
0.667
2.667
2.000

6-Aminocaproate (oxidative TCA cycle)
1.000
1.000
0.667
→
0.667
2.667
2.000

Caprolactam (via 6-aminocaproate)
1.000
1.000
0.667
→
0.667
3.333
2.000

Hexamethylenediamine (oxidative TCA cycle)
1.000
0.333
1.333
→
0.667
2.667
2.000

In the products marked “oxidative TCA cycle”, the maximum yield stoichiometries assume that the TCA cycle enzymes (e.g., malate dehydrogenase, fumarase, fumarate reductase, and succinyl-CoA ligase) are not utilized for product formation in the reductive direction. Exclusive use of the oxidative TCA cycle for product formation can be advantageous for succinyl-CoA derived products such as 3-hydroxyisobutyrate, 1,4-butanediol, adipate, 6-aminocaproate, and hexamethylenediamine because it enables all of the product pathway flux to originate from alpha-ketoglutarate dehydrogenase—an irreversible enzyme in vivo.

Notably, when these product pathways are applied in combination with an acetyl CoA pathway comprising Phosphoketolase (e.g., steps T, U, V, W, X of FIG. 1), an increased maximum theoretical yield can be obtained as shown below:

Product
C6H1206
O2
NH3

Product
H2O
CO2

1,3-Butanediol
1.000
0.000
0.000
→
1.091
0.545
1.636

Crotyl Alcohol
1.000
0.000
0.000
→
1.091
1.636
1.636

3-Buten-2-ol
1.000
0.000
0.000
→
1.091
1.636
1.636

Butadiene
1.000
0.107
0.000
→
1.071
2.786
1.714

2-Hydroxyisobutyrate
1.000
0.014
0.000
→
1.330
0.679
0.679

Methacrylate (via 2-hydroxyisobutyrate)
1.000
0.014
0.000
→
1.330
2.009
0.679

3-Hydroxyisobutyrate (oxidative TCA cycle)
1.000
0.600
0.000
→
1.200
1.200
1.200

Methacrylate (via 3-hydroxyisobutyrate)
1.000
0.600
0.000
→
1.200
2.400
1.200

1,4-Butanediol (oxidative TCA cycle)
1.000
0.124
0.000
→
1.068
0.658
1.727

Adipate (oxidative TCA cycle)
1.000
0.429
0.000
→
0.857
1.714
0.857

6-Aminocaproate (oxidative TCA cycle)
1.000
0.000
0.800
→
0.800
2.000
1.200

Caprolactam (via 6-aminocaproate)
1.000
0.000
0.800
→
0.800
2.800
1.200

Hexamethylenediamine (oxidative TCA cycle)
1.000
0.064
1.397
→
0.698
2.508
1.810

Butadiene via 2,4-pentadienoate
1
0.000
0.000
→
1.091
2.727
1.636

As with glucose, a similar yield increase can occur with use of a phosphoketolase enzyme on other carbohydrates such as glycerol, sucrose, fructose, xylose, arabinose and galactose.

Pathways identified herein, and particularly pathways exemplified in specific combinations presented herein, are superior over other pathways based in part on the applicant's ranking of pathways based on attributes Additional benefits and superior aspects include one or more of the following: maximum theoretical compound yield, maximal carbon flux, better efficiency of ATP production and reducing equivalents availability, reduced requirement for aeration, minimal production of CO₂, pathway length, number of non-native steps, thermodynamic feasibility, number of enzymes active on pathway substrates or structurally similar substrates, and having steps with currently characterized enzymes, and furthermore, the latter pathways are even more favored by having in addition at least the fewest number of non-native steps required, the most enzymes known active on pathway substrates or structurally similar substrates, and the fewest total number of steps from central metabolism.

In some embodiments, the invention also provides a method for producing a bioderived compound described herein. Such a method can comprise culturing the non-naturally occurring microbial organism as described herein under conditions and for a sufficient period of time to produce the bioderived compound. In another embodiment, method further includes separating the bioderived compound from other components in the culture. In this aspect, separating can include extraction, continuous liquid-liquid extraction, pervaporation, membrane filtration, membrane separation, reverse osmosis, electrodialysis, distillation, crystallization, centrifugation, extractive filtration, ion exchange chromatography, absorption chromatography, or ultrafiltration.

In some embodiments, depending on the bioderived compound, the method of the invention may further include chemically converting a bioderived compound to the directed final compound. For example, in some embodiments, wherein the bioderived compound is butadiene, the method of the invention can further include chemically dehydrating 1,3-butanediol, crotyl alcohol, or 3-buten-2-ol to produce the butadiene.

Suitable purification and/or assays to test for the production of acetyl-CoA, oxaloacetate, or a bioderived compound can be performed using well known methods. Suitable replicates such as triplicate cultures can be grown for each engineered strain to be tested. For example, product and byproduct formation in the engineered production host can be monitored. The final product and intermediates, and other organic compounds, can be analyzed by methods such as HPLC (High Performance Liquid Chromatography), GC-MS (Gas Chromatography-Mass Spectroscopy) and LC-MS (Liquid Chromatography-Mass Spectroscopy) or other suitable analytical methods using routine procedures well known in the art. The release of product in the fermentation broth can also be tested with the culture supernatant. Byproducts and residual glucose can be quantified by HPLC using, for example, a refractive index detector for glucose and alcohols, and a UV detector for organic acids (Lin et al., Biotechnol. Bioeng. 90:775-779 (2005)), or other suitable assay and detection methods well known in the art. The individual enzyme or protein activities from the exogenous DNA sequences can also be assayed using methods well known in the art.

The bioderived compound can be separated from other components in the culture using a variety of methods well known in the art. Such separation methods include, for example, extraction procedures as well as methods that include continuous liquid-liquid extraction, pervaporation, membrane filtration, membrane separation, reverse osmosis, electrodialysis, distillation, crystallization, centrifugation, extractive filtration, ion exchange chromatography, size exclusion chromatography, adsorption chromatography, and ultrafiltration. All of the above methods are well known in the art.

Any of the non-naturally occurring microbial organisms described herein can be cultured to produce and/or secrete the biosynthetic products of the invention. For example, the bioderived compound producers can be cultured for the biosynthetic production of a bioderived compound disclosed herein. Accordingly, in some embodiments, the invention provides culture medium having the bioderived compound or bioderived compound pathway intermediate described herein. In some aspects, the culture medium can also be separated from the non-naturally occurring microbial organisms of the invention that produced the bioderived compound or bioderived compound pathway intermediate. Methods for separating a microbial organism from culture medium are well known in the art. Exemplary methods include filtration, flocculation, precipitation, centrifugation, sedimentation, and the like.

For the production of acetyl-CoA, oxaloacetate, or a bioderived compound, the recombinant strains are cultured in a medium with carbon source and other essential nutrients. It is sometimes desirable and can be highly desirable to maintain anaerobic conditions in the fermenter to reduce the cost of the overall process. Such conditions can be obtained, for example, by first sparging the medium with nitrogen and then sealing the flasks with a septum and crimp-cap. For strains where growth is not observed anaerobically, microaerobic or substantially anaerobic conditions can be applied by perforating the septum with a small hole for limited aeration. Exemplary anaerobic conditions have been described previously and are well-known in the art. Exemplary aerobic and anaerobic conditions are described, for example, in United State publication 2009/0047719, filed Aug. 10, 2007. Fermentations can be performed in a batch, fed-batch or continuous manner, as disclosed herein. Fermentations can also be conducted in two phases, if desired. The first phase can be aerobic to allow for high growth and therefore high productivity, followed by an anaerobic phase of high acetyl-CoA, oxaloacetate, or a bioderived compound yields.

If desired, the pH of the medium can be maintained at a desired pH, in particular neutral pH, such as a pH of around 7 by addition of a base, such as NaOH or other bases, or acid, as needed to maintain the culture medium at a desirable pH. The growth rate can be determined by measuring optical density using a spectrophotometer (600 nm), and the glucose uptake rate by monitoring carbon source depletion over time.

The growth medium, can include, for example, any carbohydrate source which can supply a source of carbon to the non-naturally occurring microbial organism of the invention. Such sources include, for example, sugars such as glucose, xylose, arabinose, galactose, mannose, fructose, sucrose and starch; or glycerol, alone as the sole source of carbon or in combination with other carbon sources described herein or known in the art. In one embodiment, the carbon source is a sugar. In one embodiment, the carbon source is a sugar-containing biomass. In some embodiments, the sugar is glucose. In one embodiment, the sugar is xylose. In another embodiment, the sugar is arabinose. In one embodiment, the sugar is galactose. In another embodiment, the sugar is fructose. In other embodiments, the sugar is sucrose. In one embodiment, the sugar is starch. In certain embodiments, the carbon source is glycerol. In some embodiments, the carbon source is crude glycerol. In one embodiment, the carbon source is crude glycerol without treatment. In other embodiments, the carbon source is glycerol and glucose. In another embodiment, the carbon source is methanol and glycerol. In one embodiment, the carbon source is carbon dioxide. In one embodiment, the carbon source is formate. In one embodiment, the carbon source is methane. In one embodiment, the carbon source is methanol. In certain embodiments, methanol is used alone as the sole source of carbon or in combination with other carbon sources described herein or known in the art. In a specific embodiment, the methanol is the only (sole) carbon source. In one embodiment, the carbon source is chemoelectro-generated carbon (see, e.g., Liao et al. (2012) Science 335:1596). In one embodiment, the chemoelectro-generated carbon is methanol. In one embodiment, the chemoelectro-generated carbon is formate. In one embodiment, the chemoelectro-generated carbon is formate and methanol. In one embodiment, the carbon source is a carbohydrate and methanol. In one embodiment, the carbon source is a sugar and methanol. In another embodiment, the carbon source is a sugar and glycerol. In other embodiments, the carbon source is a sugar and crude glycerol. In yet other embodiments, the carbon source is a sugar and crude glycerol without treatment. In one embodiment, the carbon source is a sugar-containing biomass and methanol. In another embodiment, the carbon source is a sugar-containing biomass and glycerol. In other embodiments, the carbon source is a sugar-containing biomass and crude glycerol. In yet other embodiments, the carbon source is a sugar-containing biomass and crude glycerol without treatment. In some embodiments, the carbon source is a sugar-containing biomass, methanol and a carbohydrate. Other sources of carbohydrate include, for example, renewable feedstocks and biomass. Exemplary types of biomasses that can be used as feedstocks in the methods provided herein include cellulosic biomass, hemicellulosic biomass and lignin feedstocks or portions of feedstocks. Such biomass feedstocks contain, for example, carbohydrate substrates useful as carbon sources such as glucose, xylose, arabinose, galactose, mannose, fructose and starch. Given the teachings and guidance provided herein, those skilled in the art will understand that renewable feedstocks and biomass other than those exemplified above also can be used for culturing the microbial organisms provided herein for the production of succinate and other pathway intermediates. In one embodiment, the carbon source is glycerol. In certain embodiments, the glycerol carbon source is crude glycerol or crude glycerol without further treatment. In a further embodiment, the carbon source comprises glycerol or crude glycerol, and also sugar or a sugar-containing biomass, such as glucose. In a specific embodiment, the concentration of glycerol in the fermentation broth is maintained by feeding crude glycerol, or a mixture of crude glycerol and sugar (e.g., glucose). In certain embodiments, sugar is provided for sufficient strain growth. In some embodiments, the sugar (e.g., glucose) is provided at a molar concentration ratio of glycerol to sugar of from 200:1 to 1:200.

In one embodiment, the carbon source is methanol or formate. In certain embodiments, methanol is used as a carbon source in a formaldehyde fixation pathway provided herein. In one embodiment, the carbon source is methanol or formate. In other embodiments, formate is used as a carbon source in a formaldehyde fixation pathway provided herein. In specific embodiments, methanol is used as a carbon source in a methanol oxidation pathway provided herein, either alone or in combination with the fatty alcohol, fatty aldehyde, fatty acid or isopropanol pathways provided herein. In one embodiment, the carbon source is methanol. In another embodiment, the carbon source is formate.

In one embodiment, the carbon source comprises methanol, and sugar (e.g., glucose) or a sugar-containing biomass. In another embodiment, the carbon source comprises formate, and sugar (e.g., glucose) or a sugar-containing biomass. In one embodiment, the carbon source comprises methanol, formate, and sugar (e.g., glucose) or a sugar-containing biomass. In specific embodiments, the methanol or formate, or both, in the fermentation feed is provided as a mixture with sugar (e.g., glucose) or sugar-comprising biomass. In certain embodiments, sugar is provided for sufficient strain growth.

In certain embodiments, the carbon source comprises formate and a sugar (e.g., glucose). In some embodiments, the sugar (e.g., glucose) is provided at a molar concentration ratio of formate to sugar of from 200:1 to 1:200. Accordingly, given the teachings and guidance provided herein, those skilled in the art will understand that a non-naturally occurring microbial organism can be produced that secretes the biosynthesized compounds of the invention when grown on a carbon source such as a carbohydrate. Such compounds include, for example, acetyl-CoA or a bioderived compound and any of the intermediate metabolites in the acetyl-CoA or the bioderived compound pathway. All that is required is to engineer in one or more of the required enzyme or protein activities to achieve biosynthesis of the desired compound or intermediate including, for example, inclusion of some or all of the acetyl-CoA or the bioderived compound biosynthetic pathways. Accordingly, the invention provides a non-naturally occurring microbial organism that produces and/or secretes acetyl-CoA or a bioderived compound when grown on a carbohydrate or other carbon source and produces and/or secretes any of the intermediate metabolites shown in the acetyl-CoA or the bioderived compound pathway when grown on a carbohydrate or other carbon source. The acetyl-CoA or the bioderived compound producing microbial organisms of the invention can initiate synthesis from an intermediate, for example, F6P, E4P, formate, formyl-CoA, G3P, PYR, DHA, H6P, 3HBCOA, 3HB, 3-hydroxybutyryl phosphate, 4-hydroxybutyrate, 4-hydroxybutyryl-CoA, adipyl-CoA, adipate semialdehyde, 3-hydroxyisobutyrate, or 2-hydroxyisobutyryl-CoA.

The non-naturally occurring microbial organisms of the invention are constructed using methods well known in the art as exemplified herein to exogenously express at least one nucleic acid encoding an acetyl-CoA or a bioderived compound pathway enzyme or protein in sufficient amounts to produce acetyl-CoA or a bioderived compound. It is understood that the microbial organisms of the invention are cultured under conditions sufficient to produce acetyl-CoA or a bioderived compound. Following the teachings and guidance provided herein, the non-naturally occurring microbial organisms of the invention can achieve biosynthesis of a bioderived compound resulting in intracellular concentrations between about 0.1-200 mM or more. Generally, the intracellular concentration of a bioderived compound is between about 3-150 mM, particularly between about 5-125 mM and more particularly between about 8-100 mM, including about 10 mM, 20 mM, 50 mM, 80 mM, or more. Intracellular concentrations between and above each of these exemplary ranges also can be achieved from the non-naturally occurring microbial organisms of the invention.

In some embodiments, culture conditions include anaerobic or substantially anaerobic growth or maintenance conditions. Exemplary anaerobic conditions have been described previously and are well known in the art. Exemplary anaerobic conditions for fermentation processes are described herein and are described, for example, in U.S. publication 2009/0047719, filed Aug. 10, 2007. Any of these conditions can be employed with the non-naturally occurring microbial organisms as well as other anaerobic conditions well known in the art. Under such anaerobic or substantially anaerobic conditions, the acetyl-CoA or the bioderived compound producers can synthesize a bioderived compound at intracellular concentrations of 5-10 mM or more as well as all other concentrations exemplified herein. It is understood that, even though the above description refers to intracellular concentrations, acetyl-CoA or a bioderived compound producing microbial organisms can produce a bioderived compound intracellularly and/or secrete the product into the culture medium.

Exemplary fermentation processes include, but are not limited to, fed-batch fermentation and batch separation; fed-batch fermentation and continuous separation; and continuous fermentation and continuous separation. In an exemplary batch fermentation protocol, the production organism is grown in a suitably sized bioreactor sparged with an appropriate gas. Under anaerobic conditions, the culture is sparged with an inert gas or combination of gases, for example, nitrogen, N₂/CO₂mixture, argon, helium, and the like. As the cells grow and utilize the carbon source, additional carbon source(s) and/or other nutrients are fed into the bioreactor at a rate approximately balancing consumption of the carbon source and/or nutrients. The temperature of the bioreactor is maintained at a desired temperature, generally in the range of 22-37 degrees C., but the temperature can be maintained at a higher or lower temperature depending on the growth characteristics of the production organism and/or desired conditions for the fermentation process. Growth continues for a desired period of time to achieve desired characteristics of the culture in the fermenter, for example, cell density, product concentration, and the like. In a batch fermentation process, the time period for the fermentation is generally in the range of several hours to several days, for example, 8 to 24 hours, or 1, 2, 3, 4 or 5 days, or up to a week, depending on the desired culture conditions. The pH can be controlled or not, as desired, in which case a culture in which pH is not controlled will typically decrease to pH 3-6 by the end of the run. Upon completion of the cultivation period, the fermenter contents can be passed through a cell separation unit, for example, a centrifuge, filtration unit, and the like, to remove cells and cell debris. In the case where the desired product is expressed intracellularly, the cells can be lysed or disrupted enzymatically or chemically prior to or after separation of cells from the fermentation broth, as desired, in order to release additional product. The fermentation broth can be transferred to a product separations unit. Isolation of product occurs by standard separations procedures employed in the art to separate a desired product from dilute aqueous solutions. Such methods include, but are not limited to, liquid-liquid extraction using a water immiscible organic solvent (e.g., toluene or other suitable solvents, including but not limited to diethyl ether, ethyl acetate, tetrahydrofuran (THF), methylene chloride, chloroform, benzene, pentane, hexane, heptane, petroleum ether, methyl tertiary butyl ether (MTBE), dioxane, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and the like) to provide an organic solution of the product, if appropriate, standard distillation methods, and the like, depending on the chemical characteristics of the product of the fermentation process.

In an exemplary fully continuous fermentation protocol, the production organism is generally first grown up in batch mode in order to achieve a desired cell density. When the carbon source and/or other nutrients are exhausted, feed medium of the same composition is supplied continuously at a desired rate, and fermentation liquid is withdrawn at the same rate. Under such conditions, the product concentration in the bioreactor generally remains constant, as well as the cell density. The temperature of the fermenter is maintained at a desired temperature, as discussed above. During the continuous fermentation phase, it is generally desirable to maintain a suitable pH range for optimized production. The pH can be monitored and maintained using routine methods, including the addition of suitable acids or bases to maintain a desired pH range. The bioreactor is operated continuously for extended periods of time, generally at least one week to several weeks and up to one month, or longer, as appropriate and desired. The fermentation liquid and/or culture is monitored periodically, including sampling up to every day, as desired, to assure consistency of product concentration and/or cell density. In continuous mode, fermenter contents are constantly removed as new feed medium is supplied. The exit stream, containing cells, medium, and product, are generally subjected to a continuous product separations procedure, with or without removing cells and cell debris, as desired. Continuous separations methods employed in the art can be used to separate the product from dilute aqueous solutions, including but not limited to continuous liquid-liquid extraction using a water immiscible organic solvent (e.g., toluene or other suitable solvents, including but not limited to diethyl ether, ethyl acetate, tetrahydrofuran (THF), methylene chloride, chloroform, benzene, pentane, hexane, heptane, petroleum ether, methyl tertiary butyl ether (MTBE), dioxane, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and the like), standard continuous distillation methods, and the like, or other methods well known in the art.

In addition to the culturing and fermentation conditions disclosed herein, growth condition for achieving biosynthesis of acetyl-CoA or a bioderived compound can include the addition of an osmoprotectant to the culturing conditions. In certain embodiments, the non-naturally occurring microbial organisms of the invention can be sustained, cultured or fermented as described herein in the presence of an osmoprotectant. Briefly, an osmoprotectant refers to a compound that acts as an osmolyte and helps a microbial organism as described herein survive osmotic stress. Osmoprotectants include, but are not limited to, betaines, amino acids, and the sugar trehalose. Non-limiting examples of such are glycine betaine, praline betaine, dimethylthetin, dimethylslfonioproprionate, 3-dimethylsulfonio-2-methylproprionate, pipecolic acid, dimethylsulfonioacetate, choline, L-carnitine and ectoine. In one aspect, the osmoprotectant is glycine betaine. It is understood to one of ordinary skill in the art that the amount and type of osmoprotectant suitable for protecting a microbial organism described herein from osmotic stress will depend on the microbial organism used. The amount of osmoprotectant in the culturing conditions can be, for example, no more than about 0.1 mM, no more than about 0.5 mM, no more than about 1.0 mM, no more than about 1.5 mM, no more than about 2.0 mM, no more than about 2.5 mM, no more than about 3.0 mM, no more than about 5.0 mM, no more than about 7.0 mM, no more than about 10 mM, no more than about 50 mM, no more than about 100 mM or no more than about 500 mM.

In some embodiments, the carbon feedstock and other cellular uptake sources such as phosphate, ammonia, sulfate, chloride and other halogens can be chosen to alter the isotopic distribution of the atoms present in acetyl-CoA or a bioderived compound or any acetyl-CoA or a bioderived compound pathway intermediate. The various carbon feedstock and other uptake sources enumerated above will be referred to herein, collectively, as “uptake sources.” Uptake sources can provide isotopic enrichment for any atom present in the acetyl-CoA, bioderived compound or pathway intermediate, or for side products generated in reactions diverging away from an acetyl-CoA or a bioderived compound pathway. Isotopic enrichment can be achieved for any target atom including, for example, carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, chloride or other halogens.

The invention further provides a composition comprising bioderived compound described herein and a compound other than the bioderived. The compound other than the bioderived product can be a cellular portion, for example, a trace amount of a cellular portion of, or can be fermentation broth or culture medium, or a purified or partially purified fraction thereof produced in the presence of, a non-naturally occurring microbial organism of the invention. The composition can comprise, for example, a reduced level of a byproduct when produced by an organism having reduced byproduct formation, as disclosed herein. The composition can comprise, for example, bioderived compound, or a cell lysate or culture supernatant of a microbial organism of the invention.

In certain embodiments, provided herein is a composition comprising a bioderived compound provided herein produced by culturing a non-naturally occurring microbial organism described herein. In some embodiments, the composition further comprises a compound other than said bioderived compound. In certain embodiments, the compound other than said bioderived compound is a trace amount of a cellular portion of a non-naturally occurring microbial organism described herein.

The culture conditions can include, for example, liquid culture procedures as well as fermentation and other large scale culture procedures. As described herein, particularly useful yields of the biosynthetic products of the invention can be obtained under anaerobic or substantially anaerobic culture conditions.

As described herein, one exemplary growth condition for achieving biosynthesis of acetyl-CoA or a bioderived compound includes anaerobic culture or fermentation conditions. In certain embodiments, the non-naturally occurring microbial organisms of the invention can be sustained, cultured or fermented under anaerobic or substantially anaerobic conditions. Briefly, an anaerobic condition refers to an environment devoid of oxygen. Substantially anaerobic conditions include, for example, a culture, batch fermentation or continuous fermentation such that the dissolved oxygen concentration in the medium remains between 0 and 10% of saturation. Substantially anaerobic conditions also includes growing or resting cells in liquid medium or on solid agar inside a sealed chamber maintained with an atmosphere of less than 1% oxygen. The percent of oxygen can be maintained by, for example, sparging the culture with an N₂/CO₂mixture or other suitable non-oxygen gas or gases.

The culture conditions described herein can be scaled up and grown continuously for manufacturing of acetyl-CoA or a bioderived compound. Exemplary growth procedures include, for example, fed-batch fermentation and batch separation; fed-batch fermentation and continuous separation, or continuous fermentation and continuous separation. All of these processes are well known in the art. Fermentation procedures are particularly useful for the biosynthetic production of commercial quantities of acetyl-CoA or a bioderived compound. Generally, and as with non-continuous culture procedures, the continuous and/or near-continuous production of acetyl-CoA or a bioderived compound will include culturing a non-naturally occurring acetyl-CoA or a bioderived compound producing organism of the invention in sufficient nutrients and medium to sustain and/or nearly sustain growth in an exponential phase. Continuous culture under such conditions can include, for example, growth or culturing for 1 day, 2, 3, 4, 5, 6 or 7 days or more. Additionally, continuous culture can include longer time periods of 1 week, 2, 3, 4 or 5 or more weeks and up to several months. Alternatively, organisms of the invention can be cultured for hours, if suitable for a particular application. It is to be understood that the continuous and/or near-continuous culture conditions also can include all time intervals in between these exemplary periods. It is further understood that the time of culturing the microbial organism of the invention is for a sufficient period of time to produce a sufficient amount of product for a desired purpose.

Fermentation procedures are well known in the art. Briefly, fermentation for the biosynthetic production of acetyl-CoA or a bioderived compound can be utilized in, for example, fed-batch fermentation and batch separation; fed-batch fermentation and continuous separation, or continuous fermentation and continuous separation. Examples of batch and continuous fermentation procedures are well known in the art.

In addition to the above fermentation procedures using the acetyl-CoA or the bioderived compound producers of the invention for continuous production of substantial quantities of acetyl-CoA or a bioderived compound, the acetyl-CoA or the bioderived compound producers also can be, for example, simultaneously subjected to chemical synthesis and/or enzymatic procedures to convert the product to other compounds or the product can be separated from the fermentation culture and sequentially subjected to chemical and/or enzymatic conversion to convert the product to other compounds, if desired.

It is understood that modifications which do not substantially affect the activity of the various embodiments of this invention are also provided within the definition of the invention provided herein. Accordingly, the following examples are intended to illustrate but not limit the present invention.

Example I
Example I: Construction of glk-glf Libraries

The PTS system of sugar transport was inactivated by removing ptsI from E. coli K12 MG1655 strain that had deletions to remove some competing byproducts. Expectedly, the strain had a very poor growth. As mentioned, similar effects will be observed for E. coli strains with other genetic changes as well. This strain did not form colonies on M9 agar+2% glucose (after 2 days at 37° C.), and shows little/no growth in MM9+2% glucose media.

Therefore, expression mutants of native glk and Zymomonas mobilis glf (GI no: 155589) were made and inserted into the PTS− cells to increase glucose consumption and by selecting for those mutants that had an improved growth rate on glucose. The mutant library is constructed by inserting the glf gene in proximity and divergent to the glk gene. Accompanying the glf gene are divergent and degenerate promoters that tune expression of the glf and glk genes, respectively.

Promoter-glf Cassette Construction:

The promoter-glf cassette (termed “PX2-glf”) was constructed by two rounds of PCR. The first round PCR amplified the P115 promoter-glf-terminator sequence from PZS*13S-P115-glf using a partially-degenerate sequence for the P115 promoter region. A partially-degenerate ultramer (IDT) was used in the second round of PCR to construct the full length cassette. The resulting library of DNA has 6 degenerate sites in the promoter controlling glk expression, and 3 degenerate sites in the promoter controlling glf expression.

Insertion of Glf Library into the Chromosome in a ptsI− Strain:

gblocks were designed to insert the sacB-kan cassette (5′glk-SBK) or the PX2-glf cassette into the chromosome of the ptsI− strain described above, exactly 20 bp upstream of the glk gene. After selection for recombinants on sucrose, sequencing showed nucleotide degeneracy at all 9 promoter sites.

Selection for Improved Growth on Glucose:

Following creation of the mutant library a portion of the cells were selected for growth on sucrose to remove non-recombinant cells that do not have the PX2-glf cassette. As a negative control, cells that were not treated with the PX2-glf cassette were propagated in parallel. After sucrose selection, an aliquot of cells from each population were plated on M9 agar+2% glucose. Isolates were sequenced and tested for growth in MM9+2% glucose in the Bioscreen instrument (Variants 25-36 & 61-84).

FIG. 13 illustrates steps in the construction of the glk-glf libraries.

Direct Selection for Improved Glucose Consumption:

Following electroporation of the PX2-glf cassette into 6972, an aliquot of these cells was used to inoculate a 1 L capped bottle of MM9 media containing 2% glucose and 100 mM sodium bicarbonate. As a negative control, cells that were not treated with the PX2-glf cassette were propagated in parallel. Growth selection on glucose was carried out for 5 days. Aliquots were taken after 3 days and 5 days and plated on the M9 glucose agar. Diverse colony sizes were observed on the M9 glucose agar plates, and generally, colonies arose faster from the population treated with the PX2-glf DNA. Isolates were sequenced and tested for growth in MM9+2% glucose in the Bioscreen instrument (Variants 1-24, 37-60, 85-130).

Bioscreen Growth Results:

Following growth selections in glucose, variants were isolated as colonies on M9 agar plates containing glucose. 130 variants were tested for growth on MM9+2% glucose in the Bioscreen, in duplicate. The fastest growing variants from each of the selection conditions were retested for growth in the Bioscreen in replicates of 10. Included in the growth experiment are the PTS+ grandparent (6770) and the PTS− parent (6850). The PTS+ grandparent 6770 is MG1655 with deletions of adhE, ldhA and frmR.

The growth curves are shown in FIG. 14A, average of 10 replicates. Maximum growth rates (rmax in 1/hr on the x axis below) of select variants and parent strains are shown in FIG. 14B based on 10 replicates.

Example II
Coexpression of the PTS and Non-PTS System of Glucose Transport with PK in E. coli Cells Making 1,4-Butanediol

An F6P phosphoketolase (EC 4.1.2.22, Genbank ID number 118765289), was cloned from Bifidobacterium adolescentis into a plasmid suitable for expression in E. coli, plasmid pZS*13S obtained from R. Lutz (Expressys, Germany). These plasmids are based on the pZ Expression System (Lutz, R. & Bujard, H., Independent and tight regulation of transcriptional units in Escherichia coli via the LacR/O, the TetR/O and AraC/I1-I2 regulatory elements. Nucleic Acids Res. 25, 1203-1210 (1997)).

E. coli strain MG1655 variant having a pathway to produce 1,4-butanediol via alpha-ketoglutarate (designated 7542 herein) was transformed with the expression plasmid and selected and maintained using antibiotic selection with carbenicillin. This strain had a glk-glf cassette described in Example I inserted into the chromosome. The insertion site was upstream of glk.

Fermentation runs comparing the performance of the host strain with and without phosphoketolase showed an increase in BDO titer by approximately 10 g/L (FIG. 12A). Quite interestingly, it led to a reduction in pyruvate and alanine formation (FIGS. 12B and C), typical of BDO-producing strains coexpressing the PTS and the Non-PTS systems of glucose transport. This was a completely unexpected result. Additionally, the pyruvate production in the parent strain indicated a very odd profile consistent with the production, consumption and re-production of pyruvate.

Example III
Attenuation of pykF in a Strain Expressing the Non-PTS System of Sugar Transport and PK

Pyruvate kinase isozyme pykF was deleted from the E. coli K12 variant of the previous example that had the PTS system of sugar transport deleted (by ptsI deletion) and that expressed a Non-PTS system by insertion of a glk-glf cassette #25, described in Example I above. Fructose-6-phosphate phosphoketolase, E.C. 4.1.2.22, Genbank ID number 118765289, was cloned from Bifidobacterium adolescentis into a plasmid suitable for expression in E. coli plasmid pZS*13S obtained from R. Lutz (Expressys, Germany) and which is based on the pZ Expression System (Lutz, R. & Bujard, H., Independent and tight regulation of transcriptional units in Escherichia coli via the LacR/O, the TetR/O and AraC/I1-I2 regulatory elements. Nucleic Acids Res. 25, 1203-1210 (1997)). The parent strain had the PTS system deleted and the non-PTS system enhance as described previously. Additionally, PK was expressed at different levels with promoters of various strengths. EV represents the empty vector and the promoter strength in increasing order is: p115<p105<p108<p100. The results showed an optimal level of PK expression for each strain and this was the levels provided by either the p108 or the p105 promoter. As shown in the table below, the deletion of pykF in conjunction with the optimal levels of PK led to an increase in BDO production. Quite interestingly and unexpectedly, it also led to a decrease in pyruvate production, an overflow metabolism byproduct and a key challenge with the BDO-producing strains that express the Non-PTS system of glucose transport either solely or in combination with the PTS-system of glucose transport. Experiments done earlier (not shown here) with overexpression (OE) of PK with a strain that had the PTS deleted and non-PTS enhanced did not show such reduction in pyruvate.

Strains

7245(glk-glf25ΔptsI)
7424(glk-glf25ΔptsIΔpykF)

p100-EV
p115-PK
p105-PK
p108-PK
p100-PK
p100-EV
p115-PK
p105-PK
p108-PK p100-PK

BDO
157.02
159.57
173.21
166.43
125.79
109.42
158.59
187.51
208.03
157.92

4HB
0.95
1.27
2.67
1.3
1.6
1.51
3.93
13.57
13.2
3.26

Pyruvate
79.27
74.66
73.55
72.74
66.51
73.29
65.68
27.17
31.27
29.59

Acetate
2.07
3.64
5.84
13.92
23.63
5.38
7.12
8.03
8.64
16.43

Ethanol
5.13
5.27
7.41
8.89
8.68
1.79
2.37
3.84
5.13
7.31

OD
4.11
4.13
4.01
5.04
4.08
4.63
4.33
3.27
3.9
4.74

Example IV
Additional Pathways and Enzymes

This example describes enzymatic pathways for converting pyruvate to formaldehyde, and optionally in combination with producing acetyl-CoA and/or reproducing pyruvate as described in the text above.

Step Y, FIG. 1: Glyceraldehydes-3-phosphate Dehydrogenase and Enzymes of Lower Glycolysis

Enzymes comprising Step Y, G3P to PYR include: Glyceraldehyde-3-phosphate dehydrogenase; Phosphoglycerate kinase; Phosphoglyceromutase; Enolase; Pyruvate kinase or PTS-dependent substrate import.

Glyceraldehyde-3-phosphate dehydrogenase enzymes include: NADP-dependent glyceraldehyde-3-phosphate dehydrogenase, exemplary enzymes are:

Protein
GenBank ID
GI Number
Organism

gapN
AAA91091.1
642667

Streptococcus mutans

NP-GAPDH
AEC07555.1
330252461

Arabidopsis thaliana

GAPN
AAM77679.2
82469904

Triticum aestivum

gapN
CAI56300.1
87298962

Clostridium acetobutylicum

NADP-
2D2I_A
112490271

Synechococcus elongatus

GAPDH

PCC 7942

NADP-
CAA62619.1
4741714

Synechococcus elongatus

GAPDH

PCC 7942

GDP1
XP_455496.1
50310947

Kluyveromyces lactis

NRRL Y-1140

HP1346
NP_208138.1
15645959

Helicobacter pylori 26695

and NAD-dependent glyceraldehyde-3-phosphate dehydrogenase, exemplary enzymes are:

Protein
GenBank ID
GI Number
Organism

TDH1
NP_012483.1
6322409

Saccharomyces cerevisiae

s288c

TDH2
NP_012542.1
6322468

Saccharomyces cerevisiae

s288c

TDH3
NP_011708.1
632163

Saccharomyces cerevisiae

s288c

KLLA0A11858g
XP_451516.1
50303157

Kluyveromyces lactis NRRL

Y-1140

KLLA0F20988g
XP_456022.1
50311981

Kluyveromyces lactis NRRL

Y-1140

ANI_1_256144
XP_001397496.1
145251966

Aspergillus niger CBS

513.88

YALI0C06369g
XP_501515.1
50548091

Yarrowia lipolytica

CTRG_05666
XP_002551368.1
255732890

Candida tropicalis MYA-

3404

HPODL_1089
EFW97311.1
320583095

Hansenula polymorpha

DL-1

gapA
YP_490040.1
388477852

Escherichia coli

Phosphoglycerate kinase enzymes include:

Protein
GenBank ID
GI Number
Organism

PGK1
NP_009938.2
10383781

Saccharomyces cerevisiae

s288c

PGK
BAD83658.1
57157302

Candida boidinii

PGK
EFW98395.1
320584184

Hansenula polymorpha DL-1

Pgk
EIJ77825.1
387585500

Bacillus methanolicus MGA3

Pgk
YP_491126.1
388478934

Escherichia coli

Phosphoglyceromutase (aka phosphoglycerate mutase) enzymes include;

Protein
GenBank ID
GI Number
Organism

GPM1
NP_012770.1
6322697

Saccharomyces

cerevisiae s288c

GPM2
NP_010263.1
6320183

Saccharomyces

cerevisiae s288c

GPM3
NP_014585.1
6324516

Saccharomyces

cerevisiae s288c

HPODL_1391
EFW96681.1
320582464

Hansenula polymorpha

DL-1

HPODL_0376
EFW97746.1
320583533

Hansenula polymorpha

DL-1

gpmI
EIJ77827.1
387585502

Bacillus methanolicus

MGA3

gpmA
YP_489028.1
388476840

Escherichia coli

gpmM
AAC76636.1
1790041

Escherichia coli

Enolase (also known as phosphopyruvate hydratase and 2-phosphoglycerate dehydratase) enzymes include:

Protein
GenBank ID
GI Number
Organism

ENO1
NP_011770.3
398366315

Saccharomyces cerevisiae

s288c

ENO2
AAB68019.1
458897

Saccharomyces cerevisiae

s288c

HPODL_2596
EFW95743.1
320581523

Hansenula polymorpha DL-1

Eno
EIJ77828.1
387585503

Bacillus methanolicus MGA3

Eno
AAC75821.1
1789141

Escherichia coli

Pyruvate kinase (also known as phosphoenolpyruvate kinase and phosphoenolpyruvate kinase) or PTS-dependent substrate import enzymes include those below. Pyruvate kinase, also known as phosphoenolpyruvate synthase (EC 2.7.9.2), converts pyruvate and ATP to PEP and AMP. This enzyme is encoded by the PYK1 (Burke et al., J. Biol. Chem. 258:2193-2201 (1983)) and PYK2 (Boles et al., J. Bacteriol. 179:2987-2993 (1997)) genes in S. cerevisiae. In E. coli, this activity is catalyzed by the gene products of pykF and pykA. Note that pykA and pykF are genes encoding separate enzymes potentially capable of carrying out the PYK reaction. Selected homologs of the S. cerevisiae enzymes are also shown in the table below.

Protein
GenBank ID
GI Number
Organism

PYK1
NP_009362
6319279

Saccharomyces cerevisiae

PYK2
NP_014992
6324923

Saccharomyces cerevisiae

pykF
NP_416191.1
16129632

Escherichia coli

PYkA
NP_416368.1
16129807

Escherichia coli

KLLA0F23397g
XP_456122.1
50312181

Kluyveromyces lactis

CaO19.3575
XP_714934.1
68482353

Candida albicans

CaO19.11059
XP_714997.1
68482226

Candida albicans

YALI0F09185p
XP_505195
210075987

Yarrowia lipolytica

ANI_1_1126064
XP_001391973
145238652

Aspergillus niger

MGA3_03005
EIJ84220.1
387591903

Bacillus methanolicus

MGA3

HPODL_1539
EFW96829.1
320582612

Hansenula polymorpha

DL-1

PTS-dependent substrate uptake systems catalyze a phosphotransfer cascade that couples conversion of PEP to pyruvate with the transport and phosphorylation of carbon substrates. For example, the glucose PTS system transports glucose, releasing glucose-6-phosphate into the cytoplasm and concomitantly converting phosphoenolpyruvate to pyruvate. PTS systems are comprised of substrate-specific and non-substrate-specific enzymes or proteins (components). In E. coli the two non-specific components are encoded by ptsI (Enzyme I) and ptsH (HPr). The sugar-dependent components are encoded by crr and ptsG. Pts systems have been extensively studied and are reviewed, for example in Postma et al, Microbiol Rev 57: 543-94 (1993).

Protein
GenBank ID
GI Number
Organism

ptsG
AC74185.1
1787343

Escherichia coli

ptsI
AAC75469.1
1788756

Escherichia coli

ptsH
AAC75468.1
1788755

Escherichia coli

Crr
AAC75470.1
1788757

Escherichia coli

The IIA[Glc] component mediates the transfer of the phosphoryl group from histidine protein Hpr (ptsH) to the IIB[Glc] (ptsG) component. A truncated variant of the crr gene was introduced into 1,4-butanediol producing strains.

Alternatively, Phosphoenolpyruvate phosphatase (EC 3.1.3.60) catalyzes the hydrolysis of PEP to pyruvate and phosphate. Numerous phosphatase enzymes catalyze this activity, including alkaline phosphatase (EC 3.1.3.1), acid phosphatase (EC 3.1.3.2), phosphoglycerate phosphatase (EC 3.1.3.20) and PEP phosphatase (EC 3.1.3.60). PEP phosphatase enzymes have been characterized in plants such as Vignia radiate, Bruguiera sexangula and Brassica nigra. The phytase from Aspergillus fumigates, the acid phosphatase from Homo sapiens and the alkaline phosphatase of E. coli also catalyze the hydrolysis of PEP to pyruvate (Brugger et al, Appl Microbiol Biotech 63:383-9 (2004); Hayman et al, Biochem J 261:601-9 (1989); et al, The Enzymes 3rd Ed. 4:373-415 (1971))). Similar enzymes have been characterized in Campylobacter jejuni (van Mourik et al., Microbiol. 154:584-92 (2008)), Saccharomyces cerevisiae (Oshima et al., Gene 179:171-7 (1996)) and Staphylococcus aureus (Shah and Blobel, J. Bacteriol. 94:780-1 (1967)). Enzyme engineering and/or removal of targeting sequences may be required for alkaline phosphatase enzymes to function in the cytoplasm.

Protein
GenBank ID
GI Number
Organism

phyA
O00092.1
41017447

Aspergillus fumigatus

Acp5
P13686.3
56757583

Homo sapiens

phoA
NP_414917.2
49176017

Escherichia coli

phoX
ZP_01072054.1
86153851

Campylobacter jejuni

PHO8
AAA34871.1
172164

Saccharomyces cerevisiae

SaurJH1_2706
YP_001317815.1
150395140

Staphylococcus aureus

Step Q, FIG. 1: Pyruvate Formate Lyase

Pyruvate formate-lyase (PFL, EC 2.3.1.54), encoded by pflB in E. coli, can convert pyruvate into acetyl-CoA and formate. The activity of PFL can be enhanced by an activating enzyme encoded by pflA (Knappe et al., Proc. Natl. Acad. Sci U.S.A. 81:1332-1335 (1984); Wong et al., Biochemistry 32:14102-14110 (1993)). Ketoacid formate-lyase (EC 2.3.1.-), also known as 2-ketobutyrate formate-lyase (KFL) and pyruvate formate-lyase 4, is the gene product of tdcE in E. coli. This enzyme catalyzes the conversion of 2-ketobutyrate to propionyl-CoA and formate during anaerobic threonine degradation, and can also substitute for pyruvate formate-lyase in anaerobic catabolism (Simanshu et al., J Biosci. 32:1195-1206 (2007)). The enzyme is oxygen-sensitive and, like PflB, can require post-translational modification by PFL-AE to activate a glycyl radical in the active site (Hesslinger et al., Mol. Microbiol 27:477-492 (1998)). A pyruvate formate-lyase from Archaeglubus fulgidus encoded by pflD has been cloned, expressed in E. coli and characterized (Lehtio et al., Protein Eng Des Sel 17:545-552 (2004)). The crystal structures of the A. fulgidus and E. coli enzymes have been resolved (Lehtio et al., J Mol. Biol. 357:221-235 (2006); Leppanen et al., Structure. 7:733-744 (1999)). Additional PFL and PFL-AE candidates are found in Lactococcus lactis (Melchiorsen et al., Appl Microbiol Biotechnol 58:338-344 (2002)), and Streptococcus mutans (Takahashi-Abbe et al., Oral. Microbiol Immunol. 18:293-297 (2003)), Chlamydomonas reinhardtii (Hemschemeier et al., Eukaryot. Cell 7:518-526 (2008b); Atteia et al., J. Biol. Chem. 281:9909-9918 (2006)) and Clostridium pasteurianum (Weidner et al., J Bacteriol. 178:2440-2444 (1996)).

Protein
GenBank ID
GI Number
Organism

pflB
NP_415423
16128870

Escherichia coli

pflA
NP_415422.1
16128869

Escherichia coli

tdcE
AAT48170.1
48994926

Escherichia coli

pflD
NP_070278.1
11499044

Archaeglubus fulgidus

Pfl
CAA03993
2407931

Lactococcus lactis

Pfl
BAA09085
1129082

Streptococcus mutans

PFL1
XP_001689719.1
159462978

Chlamydomonas reinhardtii

pflA1
XP_001700657.1
159485246

Chlamydomonas reinhardtii

Pfl
Q46266.1
2500058

Clostridium pasteurianum

Act
CAA63749.1
1072362

Clostridium pasteurianum

Step R, FIG. 1: Pyruvate Dehydrogenase, Pyruvate Ferredoxin Oxidoreductase, Pyruvate:NADP+ Oxidoreductase

The pyruvate dehydrogenase (PDH) complex catalyzes the conversion of pyruvate to acetyl-CoA (e.g., FIG. 1 Step R). The E. coli PDH complex is encoded by the genes aceEF and lpdA. Enzyme engineering efforts have improved the E. coli PDH enzyme activity under anaerobic conditions (Kim et al., J. Bacteriol. 190:3851-3858 (2008); Kim et al., Appl. Environ. Microbiol. 73:1766-1771 (2007); Zhou et al., Biotechnol. Lett. 30:335-342 (2008)). In contrast to the E. coli PDH, the B. subtilis complex is active and required for growth under anaerobic conditions (Nakano et al., 179:6749-6755 (1997)). The Klebsiella pneumoniae PDH, characterized during growth on glycerol, is also active under anaerobic conditions (Menzel et al., 56:135-142 (1997)). Crystal structures of the enzyme complex from bovine kidney (Zhou et al., 98:14802-14807 (2001)) and the E2 catalytic domain from Azotobacter vinelandii are available (Mattevi et al., Science. 255:1544-1550 (1992)). Some mammalian PDH enzymes complexes can react on alternate substrates such as 2-oxobutanoate. Comparative kinetics of Rattus norvegicus PDH and BCKAD indicate that BCKAD has higher activity on 2-oxobutanoate as a substrate (Paxton et al., Biochem. J. 234:295-303 (1986)). The S. cerevisiae PDH complex can consist of an E2 (LAT1) core that binds E1 (PDA1, PDB1), E3 (LPD1), and Protein X (PDX1) components (Pronk et al., Yeast 12:1607-1633 (1996)). The PDH complex of S. cerevisiae is regulated by phosphorylation of E1 involving PKP1 (PDH kinase I), PTC5 (PDH phosphatase I), PKP2 and PTC6. Modification of these regulators may also enhance PDH activity. Coexpression of lipoyl ligase (LplA of E. coli and AIM22 in S. cerevisiae) with PDH in the cytosol may be necessary for activating the PDH enzyme complex. Increasing the supply of cytosolic lipoate, either by modifying a metabolic pathway or media supplementation with lipoate, may also improve PDH activity.

Gene
Accession No.
GI Number
Organism

aceE
NP_414656.1
16128107

Escherichia coli

aceF
NP_414657.1
16128108

Escherichia coli

lpd
NP_414658.1
16128109

Escherichia coli

lplA
NP_418803.1
16132203

Escherichia coli

pdhA
P21881.1
3123238

Bacillus subtilis

pdhB
P21882.1
129068

Bacillus subtilis

pdhC
P21883.2
129054

Bacillus subtilis

pdhD
P21880.1
118672

Bacillus subtilis

aceE
YP_001333808.1
152968699

Klebsiella pneumoniae

aceF
YP_001333809.1
152968700

Klebsiella pneumoniae

lpdA
YP_001333810.1
152968701

Klebsiella pneumoniae

Pdha1
NP_001004072.2
124430510

Rattus norvegicus

Pdha2
NP_446446.1
16758900

Rattus norvegicus

Dlat
NP_112287.1
78365255

Rattus norvegicus

Dld
NP_955417.1
40786469

Rattus norvegicus

LAT1
NP_014328
6324258

Saccharomyces cerevisiae

PDA1
NP_011105
37362644

Saccharomyces cerevisiae

PDB1
NP_009780
6319698

Saccharomyces cerevisiae

LPD1
NP_116635
14318501

Saccharomyces cerevisiae

PDX1
NP_011709
6321632

Saccharomyces cerevisiae

AIM22
NP_012489.2
83578101

Saccharomyces cerevisiae

As an alternative to the large multienzyme PDH complexes described above, some organisms utilize enzymes in the 2-ketoacid oxidoreductase family (OFOR) to catalyze acylating oxidative decarboxylation of 2-keto-acids. Unlike the PDH complexes, PFOR enzymes contain iron-sulfur clusters, utilize different cofactors and use ferredoxin or flavodixin as electron acceptors in lieu of NAD(P)H. Pyruvate ferredoxin oxidoreductase (PFOR) can catalyze the oxidation of pyruvate to form acetyl-CoA (e.g., FIG. 1 Step R). The PFOR from Desulfovibrio africanus has been cloned and expressed in E. coli resulting in an active recombinant enzyme that was stable for several days in the presence of oxygen (Pieulle et al., J Bacteriol. 179:5684-5692 (1997)). Oxygen stability is relatively uncommon in PFORs and is believed to be conferred by a 60 residue extension in the polypeptide chain of the D. africanus enzyme. The M. thermoacetica PFOR is also well characterized (Menon et al., Biochemistry 36:8484-8494 (1997)) and was even shown to have high activity in the direction of pyruvate synthesis during autotrophic growth (Furdui et al., J Biol Chem. 275:28494-28499 (2000)). Further, E. coli possesses an uncharacterized open reading frame, ydbK, that encodes a protein that is 51% identical to the M. thermoacetica PFOR. Evidence for pyruvate oxidoreductase activity in E. coli has been described (Blaschkowski et al., Eur. J Biochem. 123:563-569 (1982)). Several additional PFOR enzymes are described in Ragsdale, Chem. Rev. 103:2333-2346 (2003). Finally, flavodoxin reductases (e.g., fqrB from Helicobacter pylori or Campylobacter jejuni (St Maurice et al., J. Bacteriol. 189:4764-4773 (2007))) or Rnf-type proteins (Seedorf et al., Proc. Natl. Acad. Sci. U.S.A. 105:2128-2133 (2008); Herrmann et al., J. Bacteriol. 190:784-791 (2008)) provide a means to generate NADH or NADPH from the reduced ferredoxin generated by PFOR. These proteins are identified below.

Protein
GenBank ID
GI Number
Organism

Por
CAA70873.1
1770208

Desulfovibrio africanus

Por
YP_428946.1
83588937

Moorella thermoacetica

ydbK
NP_415896.1
16129339

Escherichia coli

fqrB
NP_207955.1
15645778

Helicobacter pylori

fqrB
YP_001482096.1
157414840

Campylobacter jejuni

RnfC
EDK33306.1
146346770

Clostridium kluyveri

RnfD
EDK33307.1
146346771

Clostridium kluyveri

RnfG
EDK33308.1
146346772

Clostridium kluyveri

RnfE
EDK33309.1
146346773

Clostridium kluyveri

RnfA
EDK33310.1
146346774

Clostridium kluyveri

RnfB
EDK33311.1
146346775

Clostridium kluyveri

Pyruvate:NADP oxidoreductase (PNO) catalyzes the conversion of pyruvate to acetyl-CoA. This enzyme is encoded by a single gene and the active enzyme is a homodimer, in contrast to the multi-subunit PDH enzyme complexes described above. The enzyme from Euglena gracilis is stabilized by its cofactor, thiamin pyrophosphate (Nakazawa et al, Arch Biochem Biophys 411:183-8 (2003)). The mitochondrial targeting sequence of this enzyme should be removed for expression in the cytosol. The PNO protein of E. gracilis and other NADP-dependent pyruvate:NADP+ oxidoreductase enzymes are listed in the table below.

Protein
GenBank ID
GI Number
Organism

PNO
Q94IN5.1
33112418

Euglena gracilis

cgd4_690
XP_625673.1
66356990

Cryptosporidium

parvum Iowa II

TPP_PFOR_PNO
XP_002765111.11
294867463

Perkinsus marinus

ATCC 50983

Example V
Production of Reducing Equivalents

This example describes additional enzymes including those useful for generating reducing equivalents.

Formate Hydrogen Lyase (e.g. FIG. 1, Step Q)

A formate hydrogen lyase enzyme can be employed to convert formate to carbon dioxide and hydrogen. An exemplary formate hydrogen lyase enzyme can be found in Escherichia coli. The E. coli formate hydrogen lyase consists of hydrogenase 3 and formate dehydrogenase-H (Maeda et al., Appl Microbiol Biotechnol 77:879-890 (2007)). It is activated by the gene product of fhlA. (Maeda et al., Appl Microbiol Biotechnol 77:879-890 (2007)). The addition of the trace elements, selenium, nickel and molybdenum, to a fermentation broth has been shown to enhance formate hydrogen lyase activity (Soini et al., Microb. Cell Fact. 7:26 (2008)). Various hydrogenase 3, formate dehydrogenase and transcriptional activator genes are shown below.

Protein
GenBank ID
GI number
Organism

hycA
NP_417205
16130632

Escherichia coli K-12 MG1655

hycB
NP_417204
16130631

Escherichia coli K-12 MG1655

hycC
NP_417203
16130630

Escherichia coli K-12 MG1655

hycD
NP_417202
16130629

Escherichia coli K-12 MG1655

hycE
NP_417201
16130628

Escherichia coli K-12 MG1655

hycF
NP_417200
16130627

Escherichia coli K-12 MG1655

hycG
NP_417199
16130626

Escherichia coli K-12 MG1655

hycH
NP_417198
16130625

Escherichia coli K-12 MG1655

hycI
NP_417197
16130624

Escherichia coli K-12 MG1655

fdhF
NP_418503
16131905

Escherichia coli K-12 MG1655

fhlA
NP_417211
16130638

Escherichia coli K-12 MG1655

A formate hydrogen lyase enzyme also exists in the hyperthermophilic archaeon, Thermococcus litoralis (Takacs et al., BMC. Microbiol 8:88 (2008)).

Protein
GenBank ID
GI number
Organism

mhyC
ABW05543
157954626

Thermococcus litoralis

mhyD
ABW05544
157954627

Thermococcus litoralis

mhyE
ABW05545
157954628

Thermococcus litoralis

myhF
ABW05546
157954629

Thermococcus litoralis

myhG
ABW05547
157954630

Thermococcus litoralis

myhH
ABW05548
157954631

Thermococcus litoralis

fdhA
AAB94932
2746736

Thermococcus litoralis

fdhB
AAB94931
157954625

Thermococcus litoralis

Additional formate hydrogen lyase systems have been found in Salmonella typhimurium, Klebsiella pneumoniae, Rhodospirillum rubrum, Methanobacterium formicicum (Vardar-Schara et al., Microbial Biotechnology 1:107-125 (2008)).

Hydrogenase

Hydrogenase enzymes can convert hydrogen gas to protons and transfer electrons to acceptors such as ferredoxins, NAD+, or NADP+. Ralstonia eutropha H16 uses hydrogen as an energy source with oxygen as a terminal electron acceptor. Its membrane-bound uptake [NiFe]-hydrogenase is an “O2-tolerant” hydrogenase (Cracknell, et al. Proc Nat Acad Sci, 106(49) 20681-20686 (2009)) that is periplasmically-oriented and connected to the respiratory chain via a b-type cytochrome (Schink and Schlegel, Biochim. Biophys. Acta, 567 315-324 (1979); Bernhard et al., Eur. J. Biochem. 248 179-186 (1997)). R. eutropha also contains an O₂-tolerant soluble hydrogenase encoded by the Hox operon which is cytoplasmic and directly reduces NAD+ at the expense of hydrogen (Schneider and Schlegel, Biochim. Biophys. Acta 452, 66-80 (1976); Burgdorf, J. Bact. 187(9) 3122-3132(2005)). Soluble hydrogenase enzymes are additionally present in several other organisms including Geobacter sulfurreducens (Coppi, Microbiology 151, 1239-1254 (2005)), Synechocystis str. PCC 6803 (Germer, J. Biol. Chem., 284(52), 36462-36472 (2009)), and Thiocapsa roseopersicina (Rakhely, Appl. Environ. Microbiol. 70(2) 722-728 (2004)). The Synechocystis enzyme is capable of generating NADPH from hydrogen. Overexpression of both the Hox operon from Synechocystis str. PCC 6803 and the accessory genes encoded by the Hyp operon from Nostoc sp. PCC 7120 led to increased hydrogenase activity compared to expression of the Hox genes alone (Germer, J. Biol. Chem. 284(52), 36462-36472 (2009)).

Protein
GenBank ID
GI Number
Organism

HoxF
NP_942727.1
38637753

Ralstonia eutropha H16

HoxU
NP_942728.1
38637754

Ralstonia eutropha H16

HoxY
NP_942729.1
38637755

Ralstonia eutropha H16

HoxH
NP_942730.1
38637756

Ralstonia eutropha H16

HoxW
NP_942731.1
38637757

Ralstonia eutropha H16

HoxI
NP_942732.1
38637758

Ralstonia eutropha H16

HoxE
NP_953767.1
39997816

Geobacter sulfurreducens

HoxF
NP_953766.1
39997815

Geobacter sulfurreducens

HoxU
NP_953765.1
39997814

Geobacter sulfurreducens

HoxY
NP_953764.1
39997813

Geobacter sulfurreducens

HoxH
NP_953763.1
39997812

Geobacter sulfurreducens

GSU2717
NP_953762.1
39997811

Geobacter sulfurreducens

HoxE
NP_441418.1
16330690

Synechocystis str. PCC 6803

HoxF
NP_441417.1
16330689

Synechocystis str. PCC 6803

Unknown
NP_441416.1
16330688

Synechocystis str. PCC 6803

HoxU
NP_441415.1
16330687

Synechocystis str. PCC 6803

HoxY
NP_441414.1
16330686

Synechocystis str. PCC 6803

Unknown
NP_441413.1
16330685

Synechocystis str. PCC 6803

Unknown
NP_441412.1
16330684

Synechocystis str. PCC 6803

HoxH
NP_441411.1
16330683

Synechocystis str. PCC 6803

HypF
NP_484737.1
17228189

Nostoc sp. PCC 7120

HypC
NP_484738.1
17228190

Nostoc sp. PCC 7120

HypD
NP_484739.1
17228191

Nostoc sp. PCC 7120

Unknown
NP_484740.1
17228192

Nostoc sp. PCC 7120

HypE
NP_484741.1
17228193

Nostoc sp. PCC 7120

HypA
NP_484742.1
17228194

Nostoc sp. PCC 7120

HypB
NP_484743.1
17228195

Nostoc sp. PCC 7120

Hox1E
AAP50519.1
37787351

Thiocapsa roseopersicina

Hox1F
AAP50520.1
37787352

Thiocapsa roseopersicina

Hox1U
AAP50521.1
37787353

Thiocapsa roseopersicina

Hox1Y
AAP50522.1
37787354

Thiocapsa roseopersicina

Hox1H
AAP50523.1
37787355

Thiocapsa roseopersicina

The genomes of E. coli and other enteric bacteria encode up to four hydrogenase enzymes (Sawers, G., Antonie Van Leeuwenhoek 66:57-88 (1994); Sawers et al., J Bacteriol. 164:1324-1331 (1985); Sawers and Boxer, Eur. J Biochem. 156:265-275 (1986); Sawers et al., J Bacteriol. 168:398-404 (1986)). Given the multiplicity of enzyme activities E. coli or another host organism can provide sufficient hydrogenase activity to split incoming molecular hydrogen and reduce the corresponding acceptor. Endogenous hydrogen-lyase enzymes of E. coli include hydrogenase 3, a membrane-bound enzyme complex using ferredoxin as an acceptor, and hydrogenase 4 that also uses a ferredoxin acceptor. Hydrogenase 3 and 4 are encoded by the hyc and hyf gene clusters, respectively. Hydrogenase activity in E. coli is also dependent upon the expression of the hyp genes whose corresponding proteins are involved in the assembly of the hydrogenase complexes (Jacobi et al., Arch. Microbiol 158:444-451 (1992); Rangarajan et al., J Bacteriol. 190:1447-1458 (2008)). The M. thermoacetica and Clostridium ljungdahli hydrogenases are suitable for a host that lacks sufficient endogenous hydrogenase activity. M. thermoacetica and C. ljungdahli can grow with CO₂as the exclusive carbon source indicating that reducing equivalents are extracted from H₂to enable acetyl-CoA synthesis via the Wood-Ljungdahl pathway (Drake, H. L., J Bacteriol. 150:702-709 (1982); Drake and Daniel, Res Microbiol 155:869-883 (2004); Kellum and Drake, J Bacteriol. 160:466-469 (1984)). M. thermoacetica has homologs to several hyp, hyc, and hyf genes from E. coli. These protein sequences encoded for by these genes are identified by the following GenBank accession numbers. In addition, several gene clusters encoding hydrogenase functionality are present in M. thermoacetica and C. ljungdahli (see for example US 2012/0003652).

Protein
GenBank ID
GI Number
Organism

HypA
NP_417206
16130633

Escherichia coli

HypB
NP_417207
16130634

Escherichia coli

HypC
NP_417208
16130635

Escherichia coli

HypD
NP_417209
16130636

Escherichia coli

HypE
NP_417210
226524740

Escherichia coli

HypF
NP_417192
16130619

Escherichia coli

HycA
NP_417205
16130632

Escherichia coli

HycB
NP_417204
16130631

Escherichia coli

HycC
NP_417203
16130630

Escherichia coli

HycD
NP_417202
16130629

Escherichia coli

HycE
NP_417201
16130628

Escherichia coli

HycF
NP_417200
16130627

Escherichia coli

HycG
NP_417199
16130626

Escherichia coli

HycH
NP_417198
16130625

Escherichia coli

HycI
NP_417197
16130624

Escherichia coli

HyfA
NP_416976
90111444

Escherichia coli

HyfB
NP_416977
16130407

Escherichia coli

HyfC
NP_416978
90111445

Escherichia coli

HyfD
NP_416979
16130409

Escherichia coli

HyfE
NP_416980
16130410

Escherichia coli

HyfF
NP_416981
16130411

Escherichia coli

HyfG
NP_416982
16130412

Escherichia coli

HyfH
NP_416983
16130413

Escherichia coli

HyfI
NP_416984
16130414

Escherichia coli

HyfJ
NP_416985
90111446

Escherichia coli

HyfR
NP_416986
90111447

Escherichia coli

Proteins in M. thermoacetica whose genes are homologous to the E. coli hydrogenase genes are shown below.

Protein
GenBank ID
GI Number
Organism

Moth_2175
YP_431007
83590998

Moorella thermoacetica

Moth_2176
YP_431008
83590999

Moorella thermoacetica

Moth_2177
YP_431009
83591000

Moorella thermoacetica

Moth_2178
YP_431010
83591001

Moorella thermoacetica

Moth_2179
YP_431011
83591002

Moorella thermoacetica

Moth_2180
YP_431012
83591003

Moorella thermoacetica

Moth_2181
YP_431013
83591004

Moorella thermoacetica

Moth_2182
YP_431014
83591005

Moorella thermoacetica

Moth_2183
YP_431015
83591006

Moorella thermoacetica

Moth_2184
YP_431016
83591007

Moorella thermoacetica

Moth_2185
YP_431017
83591008

Moorella thermoacetica

Moth_2186
YP_431018
83591009

Moorella thermoacetica

Moth_2187
YP_431019
83591010

Moorella thermoacetica

Moth_2188
YP_431020
83591011

Moorella thermoacetica

Moth_2189
YP_431021
83591012

Moorella thermoacetica

Moth_2190
YP_431022
83591013

Moorella thermoacetica

Moth_2191
YP_431023
83591014

Moorella thermoacetica

Moth_2192
YP_431024
83591015

Moorella thermoacetica

Moth_0439
YP_429313
83589304

Moorella thermoacetica

Moth_0440
YP_429314
83589305

Moorella thermoacetica

Moth_0441
YP_429315
83589306

Moorella thermoacetica

Moth_0442
YP_429316
83589307

Moorella thermoacetica

Moth_0809
YP_429670
83589661

Moorella thermoacetica

Moth_0810
YP_429671
83589662

Moorella thermoacetica

Moth_0811
YP_429672
83589663

Moorella thermoacetica

Moth_0812
YP_429673
83589664

Moorella thermoacetica

Moth_0814
YP_429674
83589665

Moorella thermoacetica

Moth_0815
YP_429675
83589666

Moorella thermoacetica

Moth_0816
YP_429676
83589667

Moorella thermoacetica

Moth_1193
YP_430050
83590041

Moorella thermoacetica

Moth_1194
YP_430051
83590042

Moorella thermoacetica

Moth_1195
YP_430052
83590043

Moorella thermoacetica

Moth_1196
YP_430053
83590044

Moorella thermoacetica

Moth_1717
YP_430562
83590553

Moorella thermoacetica

Moth_1718
YP_430563
83590554

Moorella thermoacetica

Moth_1719
YP_430564
83590555

Moorella thermoacetica

Moth_1883
YP_430726
83590717

Moorella thermoacetica

Moth_1884
YP_430727
83590718

Moorella thermoacetica

Moth_1885
YP_430728
83590719

Moorella thermoacetica

Moth_1886
YP_430729
83590720

Moorella thermoacetica

Moth_1887
YP_430730
83590721

Moorella thermoacetica

Moth_1888
YP_430731
83590722

Moorella thermoacetica

Moth_1452
YP_430305
83590296

Moorella thermoacetica

Moth_1453
YP_430306
83590297

Moorella thermoacetica

Moth_1454
YP_430307
83590298

Moorella thermoacetica

Genes encoding hydrogenase enzymes from C. ljungdahli are shown below.

Protein
GenBank ID
GI Number
Organism

CLJU_c20290
ADK15091.1
300435324

Clostridium ljungdahli

CLJU_c07030
ADK13773.1
300434006

Clostridium ljungdahli

CLJU_c07040
ADK13774.1
300434007

Clostridium ljungdahli

CLJU_c07050
ADK13775.1
300434008

Clostridium ljungdahli

CLJU_c07060
ADK13776.1
300434009

Clostridium ljungdahli

CLJU_c07070
ADK13777.1
300434010

Clostridium ljungdahli

CLJU_c07080
ADK13778.1
300434011

Clostridium ljungdahli

CLJU_c14730
ADK14541.1
300434774

Clostridium ljungdahli

CLJU_c14720
ADK14540.1
300434773

Clostridium ljungdahli

CLJU_c14710
ADK14539.1
300434772

Clostridium ljungdahli

CLJU_c14700
ADK14538.1
300434771

Clostridium ljungdahli

CLJU_c28670
ADK15915.1
300436148

Clostridium ljungdahli

CLJU_c28660
ADK15914.1
300436147

Clostridium ljungdahli

CLJU_c28650
ADK15913.1
300436146

Clostridium ljungdahli

CLJU_c28640
ADK15912.1
300436145

Clostridium ljungdahli

In some cases, hydrogenase encoding genes are located adjacent to a CODH. In Rhodospirillum rubrum, the encoded CODH/hydrogenase proteins form a membrane-bound enzyme complex that has been indicated to be a site where energy, in the form of a proton gradient, is generated from the conversion of CO and H₂O to CO₂and H₂(Fox et al., J Bacteriol. 178:6200-6208 (1996)). The CODH-I of C. hydrogenoformans and its adjacent genes have been proposed to catalyze a similar functional role based on their similarity to the R. rubrum CODH/hydrogenase gene cluster (Wu et al., PLoS Genet. 1:e65 (2005)). The C. hydrogenoformans CODH-I was also shown to exhibit intense CO oxidation and CO₂reduction activities when linked to an electrode (Parkin et al., J Am. Chem. Soc. 129:10328-10329 (2007)).

Protein
GenBank ID
GI Number
Organism

CooL
AAC45118
1515468

Rhodospirillum rubrum

CooX
AAC45119
1515469

Rhodospirillum rubrum

CooU
AAC45120
1515470

Rhodospirillum rubrum

CooH
AAC45121
1498746

Rhodospirillum rubrum

CooF
AAC45122
1498747

Rhodospirillum rubrum

CODH (CooS)
AAC45123
1498748

Rhodospirillum rubrum

CooC
AAC45124
1498749

Rhodospirillum rubrum

CooT
AAC45125
1498750

Rhodospirillum rubrum

CooJ
AAC45126
1498751

Rhodospirillum rubrum

CODH-I
YP_360644
78043418

Carboxydothermus

(CooS-I)

hydrogenoformans

CooF
YP_360645
78044791

Carboxydothermus

hydrogenoformans

HypA
YP_360646
78044340

Carboxydothermus

hydrogenoformans

CooH
YP_360647
78043871

Carboxydothermus

hydrogenoformans

CooU
YP_360648
78044023

Carboxydothermus

hydrogenoformans

CooX
YP_360649
78043124

Carboxydothermus

hydrogenoformans

CooL
YP_360650
78043938

Carboxydothermus

hydrogenoformans

CooK
YP_360651
78044700

Carboxydothermus

hydrogenoformans

CooM
YP_360652
78043942

Carboxydothermus

hydrogenoformans

CooC
YP_360654.1
78043296

Carboxydothermus

hydrogenoformans

CooA-1
YP_360655.1
78044021

Carboxydothermus

hydrogenoformans

Some hydrogenase and CODH enzymes transfer electrons to ferredoxins. Ferredoxins are small acidic proteins containing one or more iron-sulfur clusters that function as intracellular electron carriers with a low reduction potential. Reduced ferredoxins donate electrons to Fe-dependent enzymes such as ferredoxin-NADP⁺ oxidoreductase, pyruvate:ferredoxin oxidoreductase (PFOR) and 2-oxoglutarate:ferredoxin oxidoreductase (OFOR). The H. thermophilus gene fdx1 encodes a [4Fe-4S]-type ferredoxin that is required for the reversible carboxylation of 2-oxoglutarate and pyruvate by OFOR and PFOR, respectively (Yamamoto et al., Extremophiles 14:79-85 (2010)). The ferredoxin associated with the Sulfolobus solfataricus 2-oxoacid:ferredoxin reductase is a monomeric dicluster [3Fe-4S][4Fe-4S] type ferredoxin (Park et al. 2006). While the gene associated with this protein has not been fully sequenced, the N-terminal domain shares 93% homology with the zfx ferredoxin from S. acidocaldarius. The E. coli genome encodes a soluble ferredoxin of unknown physiological function, fdx. Some evidence indicates that this protein can function in iron-sulfur cluster assembly (Takahashi and Nakamura, 1999). Additional ferredoxin proteins have been characterized in Helicobacter pylori (Mukhopadhyay et al. 2003) and Campylobacter jejuni (van Vliet et al. 2001). A 2Fe-2S ferredoxin from Clostridium pasteurianum has been cloned and expressed in E. coli (Fujinaga and Meyer, Biochemical and Biophysical Research Communications, 192(3): (1993)). Acetogenic bacteria such as Moorella thermoacetica, Clostridium carboxidivorans P7, Clostridium ljungdahli and Rhodospirillum rubrum are predicted to encode several ferredoxins, listed below.

Protein
GenBank ID
GI Number
Organism

fdx1
BAE02673.1
68163284

Hydrogenobacter thermophilus

M11214.1
AAA83524.1
144806

Clostridium pasteurianum

Zfx
AAY79867.1
68566938

Sulfolobus acidocalarius

Fdx
AAC75578.1
1788874

Escherichia coli

hp_0277
AAD07340.1
2313367

Helicobacter pylori

fdxA
CAL34484.1
112359698

Campylobacter jejuni

Moth_0061
ABC18400.1
83571848

Moorella thermoacetica

Moth_1200
ABC19514.1
83572962

Moorella thermoacetica

Moth_1888
ABC20188.1
83573636

Moorella thermoacetica

Moth_2112
ABC20404.1
83573852

Moorella thermoacetica

Moth_1037
ABC19351.1
83572799

Moorella thermoacetica

CcarbDRAFT_4383
ZP_05394383.1
255527515

Clostridium carboxidivorans P7

CcarbDRAFT_2958
ZP_05392958.1
255526034

Clostridium carboxidivorans P7

CcarbDRAFT_2281
ZP_05392281.1
255525342

Clostridium carboxidivorans P7

CcarbDRAFT_5296
ZP_05395295.1
255528511

Clostridium carboxidivorans P7

CcarbDRAFT_1615
ZP_05391615.1
255524662

Clostridium carboxidivorans P7

CcarbDRAFT_1304
ZP_05391304.1
255524347

Clostridium carboxidivorans P7

cooF
AAG29808.1
11095245

Carboxydothermus hydrogenoformans

fdxN
CAA35699.1
46143

Rhodobacter capsulatus

Rru_A2264
ABC23064.1
83576513

Rhodospirillum rubrum

Rru_A1916
ABC22716.1
83576165

Rhodospirillum rubrum

Rru_A2026
ABC22826.1
83576275

Rhodospirillum rubrum

cooF
AAC45122.1
1498747

Rhodospirillum rubrum

fdxN
AAA26460.1
152605

Rhodospirillum rubrum

Alvin_2884
ADC63789.1
288897953

Allochromatium vinosum DSM 180

Fdx
YP_002801146.1
226946073

Azotobacter vinelandii DJ

CKL_3790
YP_001397146.1
153956381

Clostridium kluyveri DSM 555

fer1
NP_949965.1
39937689

Rhodopseudomonas palustris CGA009

Fdx
CAA12251.1
3724172

Thauera aromatica

CHY_2405
YP_361202.1
78044690

Carboxydothermus hydrogenoformans

Fer
YP_359966.1
78045103

Carboxydothermus hydrogenoformans

Fer
AAC83945.1
1146198

Bacillus subtilis

fdx1
NP_249053.1
15595559

Pseudomonas aeruginosa PA01

yfhL
AP_003148.1
89109368

Escherichia coli K-12

CLJU_c00930
ADK13195.1
300433428

Clostridium ljungdahli

CLJU_c00010
ADK13115.1
300433348

Clostridium ljungdahli

CLJU_c01820
ADK13272.1
300433505

Clostridium ljungdahli

CLJU_c17980
ADK14861.1
300435094

Clostridium ljungdahli

CLJU_c17970
ADK14860.1
300435093

Clostridium ljungdahli

CLJU_c22510
ADK15311.1
300435544

Clostridium ljungdahli

CLJU_c26680
ADK15726.1
300435959

Clostridium ljungdahli

CLJU_c29400
ADK15988.1
300436221

Clostridium ljungdahli

Ferredoxin oxidoreductase enzymes transfer electrons from ferredoxins or flavodoxins to NAD(P)H. Two enzymes catalyzing the reversible transfer of electrons from reduced ferredoxins to NAD(P)+ are ferredoxin:NAD+oxidoreductase (EC 1.18.1.3) and ferredoxin:NADP+ oxidoreductase (FNR, EC 1.18.1.2). Ferredoxin:NADP+ oxidoreductase (FNR, EC 1.18.1.2) has a noncovalently bound FAD cofactor that facilitates the reversible transfer of electrons from NADPH to low-potential acceptors such as ferredoxins or flavodoxins (Blaschkowski et al., Eur. J. Biochem. 123:563-569 (1982); Fujii et al., 1977). The Helicobacter pylori FNR, encoded by HP1164 (fqrB), is coupled to the activity of pyruvate:ferredoxin oxidoreductase (PFOR) resulting in the pyruvate-dependent production of NADPH (St et al. 2007). An analogous enzyme is found in Campylobacter jejuni (St Maurice et al., J. Bacteriol. 189:4764-4773 (2007)). A ferredoxin:NADP+ oxidoreductase enzyme is encoded in the E. coli genome by fpr (Bianchi et al. 1993). Ferredoxin:NAD+ oxidoreductase utilizes reduced ferredoxin to generate NADH from NAD+. In several organisms, including E. coli, this enzyme is a component of multifunctional dioxygenase enzyme complexes. The ferredoxin:NAD+ oxidoreductase of E. coli, encoded by hcaD, is a component of the 3-phenylproppionate dioxygenase system involved in involved in aromatic acid utilization (Diaz et al. 1998). NADH:ferredoxin reductase activity was detected in cell extracts of Hydrogenobacter thermophilus, although a gene with this activity has not yet been indicated (Yoon et al. 2006). Additional ferredoxin:NAD(P)+ oxidoreductases have been annotated in Clostridium carboxydivorans P7. The NADH-dependent reduced ferredoxin: NADP oxidoreductase of C. kluyveri, encoded by nfnAB, catalyzes the concomitant reduction of ferredoxin and NAD+ with two equivalents of NADPH (Wang et al, J Bacteriol 192: 5115-5123 (2010)). Finally, the energy-conserving membrane-associated Rnf-type proteins (Seedorf et al, PNAS 105:2128-2133 (2008); and Herrmann, J. Bacteriol 190:784-791 (2008)) provide a means to generate NADH or NADPH from reduced ferredoxin.

GI

Protein
GenBank ID
Number
Organism

fqrB
NP_207955.1
15645778

Helicobacter pylori

fqrB
YP_001482096.1
157414840

Campylobacter jejuni

RPA3954
CAE29395.1
39650872

Rhodopseudomonas palustris

Fpr
BAH29712.1
225320633

Hydrogenobacter

thermophilus

yumC
NP_391091.2
255767736

Bacillus subtilis

Fpr
P28861.4
399486

Escherichia coli

hcaD
AAC75595.1
1788892

Escherichia coli

LOC100282643
NP_001149023.1
226497434

Zea mays

NfnA
YP_001393861.1
153953096

Clostridium kluyveri

NfnB
YP_001393862.1
153953097

Clostridium kluyveri

CcarbDRAFT_2639
ZP_05392639.1
255525707

Clostridium

carboxidivorans P7

CcarbDRAFT_2638
ZP_05392638.1
255525706

Clostridium

carboxidivorans P7

CcarbDRAFT_2636
ZP_05392636.1
255525704

Clostridium

carboxidivorans P7

CcarbDRAFT_5060
ZP_05395060.1
255528241

Clostridium

carboxidivorans P7

CcarbDRAFT_2450
ZP_05392450.1
255525514

Clostridium

carboxidivorans P7

CcarbDRAFT_1084
ZP_05391084.1
255524124

Clostridium

carboxidivorans P7

RnfC
EDK33306.1
146346770

Clostridium kluyveri

RnfD
EDK33307.1
146346771

Clostridium kluyveri

RnfG
EDK33308.1
146346772

Clostridium kluyveri

RnfE
EDK33309.1
146346773

Clostridium kluyveri

RnfA
EDK33310.1
146346774

Clostridium kluyveri

RnfB
EDK33311.1
146346775

Clostridium kluyveri

CLJU_c11410
ADK14209.1
300434442

Clostridium ljungdahlii

(RnfB)

CLJU_c11400
ADK14208.1
300434441

Clostridium ljungdahlii

(RnfA)

CLJU_c11390
ADK14207.1
300434440

Clostridium ljungdahlii

(RnfE)

CLJU_c11380
ADK14206.1
300434439

Clostridium ljungdahlii

(RnfG)

CLJU_c11370
ADK14205.1
300434438

Clostridium ljungdahlii

(RnfD)

CLJU_c11360
ADK14204.1
300434437

Clostridium ljungdahlii

(RnfC)

MOTH_1518
YP_430370.1
83590361

Moorella thermoacetica

(NfnA)

MOTH_1517(NfnB)
YP_430369.1
83590360

Moorella thermoacetica

CHY_1992 (NfnA)
YP_360811.1
78045020

Carboxydothermus

hydrogenoformans

CHY_1993 (NfnB)
YP_360812.1
78044266

Carboxydothermus

hydrogenoformans

CLJU_c37220
YP_003781850.1
300856866

Clostridium ljungdahlii

(NfnAB)

Formate Dehydrogenase

Formate dehydrogenase (FDH) catalyzes the reversible transfer of electrons from formate to an acceptor. See also FIG. 1 Step S. Enzymes with FDH activity utilize various electron carriers such as, for example, NADH (EC 1.2.1.2), NADPH (EC 1.2.1.43), quinols (EC 1.1.5.6), cytochromes (EC 1.2.2.3) and hydrogenases (EC 1.1.99.33). FDH enzymes have been characterized from Moorella thermoacetica (Andreesen and Ljungdahl, J Bacteriol 116:867-873 (1973); Li et al., J Bacteriol 92:405-412 (1966); Yamamoto et al., J Biol Chem. 258:1826-1832 (1983). The loci, Moth_2312 is responsible for encoding the alpha subunit of formate dehydrogenase while the beta subunit is encoded by Moth_2314 (Pierce et al., Environ Microbiol (2008)). Another set of genes encoding formate dehydrogenase activity with a propensity for CO₂reduction is encoded by Sfum_2703 through Sfum_2706 in Syntrophobacter fumaroxidans (de Bok et al., Eur J Biochem. 270:2476-2485 (2003)); Reda et al., PNAS 105:10654-10658 (2008)). A similar set of genes presumed to carry out the same function are encoded by CHY_0731, CHY_0732, and CHY_0733 in C. hydrogenoformans (Wu et al., PLoS Genet 1:e65 (2005)). Formate dehydrogenases are also found many additional organisms including C. carboxidivorans P7, Bacillus methanolicus, Burkholderia stabilis, Moorella thermoacetica ATCC 39073, Candida boidinii, Candida methylica, and Saccharomyces cerevisiae S288c. The soluble formate dehydrogenase from Ralstonia eutropha reduces NAD⁺(fdsG, -B, -A, -C, -D) (Oh and Bowien, 1998).

Several formate dehydrogenase enzymes have been identified that have higher specificity for NADP as the cofactor as compared to NAD. This enzyme has been deemed as the NADP-dependent formate dehydrogenase and has been reported from 5 species of the Burkholderia cepacia complex. It was tested and verified in multiple strains of Burkholderia multivorans, Burkholderia stabilis, Burkholderia pyrrocinia, and Burkholderia cenocepacia (Hatrongjit et al., Enzyme and Microbial Tech., 46: 557-561 (2010)). The enzyme from Burkholderia stabilis has been characterized and the apparent K_mof the enzyme were reported to be 55.5 mM, 0.16 mM and 1.43 mM for formate, NADP, and NAD respectively. More gene candidates can be identified using sequence homology of proteins deposited in Public databases such as NCBI, JGI and the metagenomic databases.

Protein
GenBank ID
GI
Organism

Moth_2312
YP_431142
148283121

Moorella thermoacetica

Moth_2314
YP_431144
83591135

Moorella thermoacetica

Sfum_2703
YP_846816.1
116750129

Syntrophobacter

Sfum_2704
YP_846817.1
116750130

Syntrophobacter

Sfum_2705
YP_846818.1
116750131

Syntrophobacter

Sfum_2706
YP_846819.1
116750132

Syntrophobacter

CHY_0731
YP_359585.1
78044572

Carboxydothermus

CHY_0732
YP_359586.1
78044500

Carboxydothermus

CHY_0733
YP_359587.1
78044647

Carboxydothermus

CcarbDRAFT_0901
ZP_05390901.1
255523938

Clostridium

CcarbDRAFT_4380
ZP_05394380.1
255527512

Clostridium

fdhA,
EIJ82879.1
387590560

Bacillus methanolicus

fdhA, PB1_11719
ZP_10131761.1
387929084

Bacillus methanolicus PB1

fdhD,
EIJ82880.1
387590561

Bacillus methanolicus

fdhD, PB1_11724
ZP_10131762.1
387929085

Bacillus methanolicus PB1

fdh
ACF35003.
194220249

Burkholderia stabilis

FDH1
AAC49766.1
2276465

Candida boidinii

fdh
CAA57036.1
1181204

Candida methylica

FDH2
P0CF35.1
294956522

Saccharomyces cerevisiae

FDH1
NP_015033.1
6324964

Saccharomyces cerevisiae

fdsG
YP_725156.1
113866667

Ralstonia eutropha

fdsB
YP_725157.1
113866668

Ralstonia eutropha

fdsA
YP_725158.1
113866669

Ralstonia eutropha

fdsC
YP_725159.1
113866670

Ralstonia eutropha

fdsD
YP_725160.1
113866671

Ralstonia eutropha

FIG. 1 Step A—Methanol Dehydrogenase

NAD+ dependent methanol dehydrogenase enzymes (EC 1.1.1.244) catalyze the conversion of methanol and NAD+ to formaldehyde and NADH, which is a first step in a methanol oxidation pathway. An enzyme with this activity was first characterized in Bacillus methanolicus (Heggeset, et al., Applied and Environmental Microbiology, 78(15):5170-5181 (2012)). This enzyme is zinc and magnesium dependent, and activity of the enzyme is enhanced by the activating enzyme encoded by act (Kloosterman et al, J Biol Chem 277:34785-92 (2002)). The act is a Nudix hydrolase. Several of these candidates have been identified and shown to have activity on methanol. Additional NAD(P)+ dependent enzymes can be identified by sequence homology. Methanol dehydrogenase enzymes utilizing different electron acceptors are also known in the art. Examples include cytochrome dependent enzymes such as mxaIF of the methylotroph Methylobacterium extorquens (Nunn et al, Nucl Acid Res 16:7722 (1988)). Methanol dehydrogenase enzymes of methanotrophs such as Methylococcus capsulatis function in a complex with methane monooxygenase (MMO) (Myronova et al, Biochem 45:11905-14 (2006)). Methanol can also be oxidized to formaldehyde by alcohol oxidase enzymes such as methanol oxidase (EC 1.1.3.13) of Candida boidinii (Sakai et al, Gene 114: 67-73 (1992)).

Protein
GenBank ID
GI Number
Organism

mdh, MGA3_17392
EIJ77596.1
387585261

Bacillus methanolicus MGA3

mdh2, MGA3_07340
EIJ83020.1
387590701

Bacillus methanolicus MGA3

mdh3, MGA3_10725
EIJ80770.1
387588449

Bacillus methanolicus MGA3

act, MGA3_09170
EIJ83380.1
387591061

Bacillus methanolicus MGA3

mdh, PB1_17533
ZP_10132907.1
387930234

Bacillus methanolicus PB1

mdh1, PB1_14569
ZP_10132325.1
387929648

Bacillus methanolicus PB1

mdh2, PB1_12584
ZP_10131932.1
387929255

Bacillus methanolicus PB1

act, PB1_14394
ZP_10132290.1
387929613

Bacillus methanolicus PB1

BFZC1_05383
ZP_07048751.1
299535429

Lysinibacillus fusiformis

BFZC1_20163
ZP_07051637.1
299538354

Lysinibacillus fusiformis

Bsph_4187
YP_001699778.1
169829620

Lysinibacillus sphaericus

Bsph_1706
YP_001697432.1
169827274

Lysinibacillus sphaericus

mdh2
YP_004681552.1
339322658

Cupriavidus necator N-1

nudF1
YP_004684845.1
339325152

Cupriavidus necator N-1

BthaA_010200007655
ZP_05587334.1
257139072

Burkholderia thailandensis E264

BTH_I1076
YP_441629.1
83721454

Burkholderia thailandensis E264

(MutT/NUDIX NTP

pyrophosphatase)

BalcAV_11743
ZP_10819291.1
402299711

Bacillus alcalophilus ATCC

27647

BalcAV_05251
ZP_10818002.1
402298299

Bacillus alcalophilus ATCC

27647

alcohol dehydrogenase
YP_001447544
156976638

Vibrio harveyi ATCC BAA-1116

P3TCK_27679
ZP_01220157.1
90412151

Photobacterium profundum

3TCK

alcohol dehydrogenase
YP_694908
110799824

Clostridium perfringens ATCC

13124

adhB
NP_717107
24373064

Shewanella oneidensis MR-1

alcohol dehydrogenase
YP_237055
66047214

Pseudomonas syringae pv.

syringae B728a

alcohol dehydrogenase
YP_359772
78043360

Carboxydothermus

hydrogenoformans Z-2901

alcohol dehydrogenase
YP_003990729
312112413

Geobacillus sp. Y4.1MC1

PpeoK3_010100018471
ZP_10241531.1
390456003

Paenibacillus peoriae KCTC

3763

OBE_12016
EKC54576
406526935

human gut metagenome

alcohol dehydrogenase
YP_001343716
152978087

Actinobacillus succinogenes

130Z

dhaT
AAC45651
2393887

Clostridium pasteurianum DSM

525

alcohol dehydrogenase
NP_561852
18309918

Clostridium perfringens str. 13

BAZO_10081
ZP_11313277.1
410459529

Bacillus azotoformans LMG 9581

alcohol dehydrogenase
YP_007491369
452211255

Methanosarcina mazei Tuc01

alcohol dehydrogenase
YP_004860127
347752562

Bacillus coagulans 36D1

alcohol dehydrogenase
YP_002138168
197117741

Geobacter bemidjiensis Bem

DesmeDRAFT_1354
ZP_08977641.1
354558386

Desulfitobacterium

metallireducens DSM 15288

alcohol dehydrogenase
YP_001337153
152972007

Klebsiella pneumoniae subsp.

pneumoniae MGH 78578

alcohol dehydrogenase
YP_001113612
134300116

Desulfotomaculum reducens MI-1

alcohol dehydrogenase
YP_001663549
167040564

Thermoanaerobacter sp. X514

ACINNAV82_2382
ZP_16224338.1
421788018

Acinetobacter baumannii Naval-

82

alcohol dehydrogenase
YP_005052855
374301216

Desulfovibrio africanus str.

Walvis Bay

alcohol dehydrogenase
AGF87161
451936849
uncultured organism

DesfrDRAFT_3929
ZP_07335453.1
303249216

Desulfovibrio fructosovorans JJ

alcohol dehydrogenase
NP_617528
20091453

Methanosarcina acetivorans C2A

alcohol dehydrogenase
NP_343875.1
15899270

Sulfolobus solfataricus P-2

adh4
YP_006863258
408405275

Nitrososphaera gargensis Ga9.2

Ta0841
NP_394301.1
16081897

Thermoplasma acidophilum

PTO1151
YP_023929.1
48478223

Picrophilus torridus DSM9790

alcohol dehydrogenase
ZP_10129817.1
387927138

Bacillus methanolicus PB-1

cgR_2695
YP_001139613.1
145296792

Corynebacterium glutamicum R

alcohol dehydrogenase
YP_004758576.1
340793113

Corynebacterium variabile

HMPREF1015_01790
ZP_09352758.1
365156443

Bacillus smithii

ADH1
NP_014555.1
6324486

Saccharomyces cerevisiae

NADH-dependent
YP_001126968.1
138896515

Geobacillus themodenitrificans

butanol

NG80-2

dehydrogenase A

alcohol dehydrogenase
WP_007139094.1
494231392

Flavobacterium frigoris

methanol
WP_003897664.1
489994607

Mycobacterium smegmatis

dehydrogenase

ADH1B
NP_000659.2
34577061

Homo sapiens

PMI01_01199
ZP_10750164.1
399072070

Caulobacter sp. AP07

YiaY
YP_026233.1
49176377

Escherichia coli

MCA0299
YP_112833.1
53802410

Methylococcus capsulatis

MCA0782
YP_113284.1
53804880

Methylococcus capsulatis

mxaI
YP_002965443.1
240140963

Methylobacterium extorquens

mxaF
YP_002965446.1
240140966

Methylobacterium extorquens

AOD1
AAA34321.1
170820

Candida boidinii

hypothetical protein
EDA87976.1
142827286

Marine metagenome

GOS_1920437

JCVI_SCAF_1096627185304

alcohol dehydrogenase
CAA80989.1
580823

Geobacillus stearothermophilus

An in vivo assay was developed to determine the activity of methanol dehydrogenases. This assay relies on the detection of formaldehyde (HCHO), thus measuring the forward activity of the enzyme (oxidation of methanol). To this end, a strain comprising a BDOP and lacking frmA, frmB, frmR was created using Lambda Red recombinase technology (Datsenko and Wanner, Proc. Natl. Acad. Sci. USA, 6 97(12): 6640-5 (2000). Plasmids expressing methanol dehydrogenases were transformed into the strain, then grown to saturation in LB medium+antibiotic at 37° C. with shaking. Transformation of the strain with an empty vector served as a negative control. Cultures were adjusted by O.D. and then diluted 1:10 into M9 medium+0.5% glucose+antibiotic and cultured at 37° C. with shaking for 6-8 hours until late log phase. Methanol was added to 2% v/v and the cultures were further incubated for 30 min. with shaking at 37° C. Cultures were spun down and the supernatant was assayed for formaldehyde produced using DETECTX Formaldehyde Detection kit (Arbor Assays; Ann Arbor, Mich.) according to manufacturer's instructions. The frmA, frmB, frmR deletions resulted in the native formaldehyde utilization pathway to be deleted, which enables the formation of formaldehyde that can be used to detect methanol dehydrogenase activity in the non-naturally occurring microbial organism.

The activity of several enzymes was measured using the assay described above. The results of four independent experiments are provided in Table 5 below.

TABLE 5

Results of in vivo assays showing formaldehyde (HCHO) production

by various non-naturally occurring microbial organism comprising

a plasmid expressing a methanol dehydrogenase.

Accession
HCHO

number
(μM)

Experiment 1

EIJ77596.1
>50

EIJ83020.1
>20

EIJ80770.1
>50

ZP_10132907.1
>20

ZP_10132325.1
>20

ZP_10131932.1
>50

ZP_07048751.1
>50

YP_001699778.1
>50

YP_004681552.1
>10

ZP_10819291.1
<1

Empty vector
2.33

Experiment 2

EIJ77596.1
>50

NP_00659.2
>50

YP_004758576.1
>20

ZP_09352758.1
>50

ZP_10129817.1
>20

YP_001139613.1
>20

NP_014555.1
>10

WP_007139094.1
>10

NP_343875.1
>1

YP_006863258
>1

NP_394301.1
>1

ZP_10750164.1
>1

YP_023929.1
>1

ZP_08977641.1
<1

ZP_10117398.1
<1

YP_004108045.1
<1

ZP_09753449.1
<1

Empty vector
0.17

Experiment 3

EIJ77596.1
>50

NP_561852
>50

YP_002138168
>50

YP_026233.1
>50

YP_001447544
>50

Metalibrary
>50

YP_359772
>50

ZP_01220157.1
>50

ZP_07335453.1
>20

YP_001337153
>20

YP_694908
>20

NP_717107
>20

AAC45651
>10

ZP_1 1313277.1
>10

ZP_16224338.1
>10

YP_001113612
>10

YP_004860127
>10

YP_003310546
>10

YP_001343716
>10

NP_717107
>10

YP_002434746
>10

Empty vector
0.11

Experiment 4

EIJ77596.1
>20

ZP_11313277.1
>50

YP_001113612
>50

YP_001447544
>20

AGF87161
>50

EDA87976.1
>20

Empty vector
−0.8

Formaldehyde Dehydrogenase

Oxidation of formaldehyde to formate is catalyzed by formaldehyde dehydrogenase. Where methanol is used as a carbon source, a host's native formaldehyde dehydrogenase can be a target for elimination or attenuation, particularly when it competes with and reduces formaldehyde assimilation that is shown in FIG. 1. An NAD+ dependent formaldehyde dehydrogenase enzyme is encoded by fdhA of Pseudomonas putida (Ito et al, J Bacteriol 176: 2483-2491 (1994)). Additional formaldehyde dehydrogenase enzymes include the NAD+ and glutathione independent formaldehyde dehydrogenase from Hyphomicrobium zavarzinii (Jerome et al, Appl Microbiol Biotechnol 77:779-88 (2007)), the glutathione dependent formaldehyde dehydrogenase of Pichia pastoris (Sunga et al, Gene 330:39-47 (2004)) and the NAD(P)+ dependent formaldehyde dehydrogenase of Methylobacter marinus (Speer et al, FEMS Microbiol Left, 121(3):349-55 (1994)).

Protein
GenBank ID
GI Number
Organism

fdhA
P46154.3
1169603

Pseudomonas putida

faoA
CAC85637.1
19912992

Hyphomicrobium zavarzinii

Fld1
CCA39112.1
328352714

Pichia pastoris

fdh
P47734.2
221222447

Methylobacter marinus

In addition to the formaldehyde dehydrogenase enzymes listed above, alternate enzymes and pathways for converting formaldehyde to formate are known in the art. For example, many organisms employ glutathione-dependent formaldehyde oxidation pathways, in which formaldehyde is converted to formate in three steps via the intermediates S-hydroxymethylglutathione and S-formylglutathione (Vorholt et al, J Bacteriol 182:6645-50 (2000)). The enzymes of this pathway are S-(hydroxymethyl)glutathione synthase (EC 4.4.1.22), glutathione-dependent formaldehyde dehydrogenase (EC 1.1.1.284) and S-formylglutathione hydrolase (EC 3.1.2.12).

Carbon Monoxide Dehydrogenase (CODH)

CODH is a reversible enzyme that interconverts CO and CO₂at the expense or gain of electrons. The natural physiological role of the CODH in ACS/CODH complexes is to convert CO₂to CO for incorporation into acetyl-CoA by acetyl-CoA synthase. Nevertheless, such CODH enzymes are suitable for the extraction of reducing equivalents from CO due to the reversible nature of such enzymes. Expressing such CODH enzymes in the absence of ACS allows them to operate in the direction opposite to their natural physiological role (i.e., CO oxidation). In M. thermoacetica, C. hydrogenoformans, C. carboxidivorans P7, and several other organisms, additional CODH encoding genes are located outside of the ACS/CODH operons. These enzymes provide a means for extracting electrons (or reducing equivalents) from the conversion of carbon monoxide to carbon dioxide. The M. thermoacetica gene (Genbank Accession Number: YP_430813) is expressed by itself in an operon and is believed to transfer electrons from CO to an external mediator like ferredoxin in a “Ping-pong” reaction. The reduced mediator then couples to other reduced nicolinamide adenine dinucleotide phosphate (NAD(P)H) carriers or ferredoxin-dependent cellular processes (Ragsdale, Annals of the New York Academy of Sciences 1125: 129-136 (2008)). The genes encoding the C. hydrogenoformans CODH-II and CooF, a neighboring protein, were cloned and sequenced (Gonzalez and Robb, FEMS Microbiol Lett. 191:243-247 (2000)). The resulting complex was membrane-bound, although cytoplasmic fractions of CODH-II were shown to catalyze the formation of NADPH suggesting an anabolic role (Svetlitchnyi et al., J Bacteriol. 183:5134-5144 (2001)). The crystal structure of the CODH-II is also available (Dobbek et al., Science 293:1281-1285 (2001)). Similar ACS-free CODH enzymes can be found in a diverse array of organisms including Geobacter metallireducens GS-15, Chlorobium phaeobacteroides DSM 266, Clostridium cellulolyticum H10, Desulfovibrio desulfuricans subsp. desulfuricans str. ATCC 27774, Pelobacter carbinolicus DSM 2380, C. ljungdahli and Campylobacter curvus 525.92.

Protein
GenBank ID
GI Number
Organism

CODH (putative)
YP_430813
83590804

Moorella thermoacetica

CODH-II (CooS-
YP_358957
78044574

Carboxydothermus

II)

hydrogenoformans

CooF
YP_358958
78045112

Carboxydothermus

hydrogenoformans

CODH (putative)
ZP_05390164.1
255523193

Clostridium carboxidivorans P7

CcarbDRAFT_0341
ZP_05390341.1
255523371

Clostridium carboxidivorans P7

CcarbDRAFT_1756
ZP_05391756.1
255524806

Clostridium carboxidivorans P7

CcarbDRAFT_2944
ZP_05392944.1
255526020

Clostridium carboxidivorans P7

CODH
YP_384856.1
78223109

Geobacter metallireducens GS-15

Cpha266_0148
YP_910642.1
119355998

Chlorobium

(cytochrome c)

phaeobacteroides DSM 266

Cpha266_0149
YP_910643.1
119355999

Chlorobium

(CODH)

phaeobacteroides DSM 266

Ccel_0438
YP_002504800.1
220927891

Clostridium cellulolyticum H10

Ddes_0382
YP_002478973.1
220903661

Desulfovibrio desulfuricans subsp.

(CODH)

desulfuricans str. ATCC 27774

Ddes_0381
YP_002478972.1
220903660

Desulfovibrio desulfuricans subsp.

(CooC)

desulfuricans str. ATCC 27774

Pcar_0057
YP_355490.1
7791767

Pelobacter carbinolicus DSM

(CODH)

2380

Pcar_0058
YP_355491.1
7791766

Pelobacter carbinolicus DSM

(CooC)

2380

Pcar_0058
YP_355492.1
7791765

Pelobacter carbinolicus DSM

(HypA)

2380

CooS (CODH)
YP_001407343.1
154175407

Campylobacter curvus 525.92

CLJU_c09110
ADK13979.1
300434212

Clostridium ljungdahli

CLJU_c09100
ADK13978.1
300434211

Clostridium ljungdahli

CLJU_c09090
ADK13977.1
300434210

Clostridium ljungdahli

Example VI
Methods for Formaldehyde Fixation (or Assimilation)

Provided herein are exemplary pathways, which utilize formaldehyde, for example produced from the oxidation of methanol (see, e.g., FIG. 1, step A) or from formate assimilation, in the formation of intermediates of certain central metabolic pathways that can be used for the production of compounds disclosed herein.

One exemplary pathway that can utilize formaldehyde produced from the oxidation of methanol is shown in FIG. 1, which involves condensation of formaldehyde and D-ribulose-5-phosphate to form hexulose-6-phosphate (h6p) by hexulose-6-phosphate synthase (FIG. 1, step B). The enzyme can use Mg²⁺or Mn²⁺for maximal activity, although other metal ions are useful, and even non-metal-ion-dependent mechanisms are contemplated. H6p is converted into fructose-6-phosphate by 6-phospho-3-hexuloisomerase (FIG. 1, step C).

Another exemplary pathway that involves the detoxification and assimilation of formaldehyde produced from the oxidation of methanol is shown in FIG. 1 and proceeds through dihydroxyacetone. Dihydroxyacetone synthase is a special transketolase that first transfers a glycoaldehyde group from xylulose-5-phosphate to formaldehyde, resulting in the formation of dihydroxyacetone (DHA) and glyceraldehyde-3-phosphate (G3P), which is an intermediate in glycolysis (FIG. 1). The DHA obtained from DHA synthase can be further phosphorylated to form DHA phosphate and assimilated into glycolysis and several other pathways (FIG. 1). Alternatively, or in addition, a fructose-6-phosphate aldolase can be used to catalyze the conversion of DHA and G3P to fructose-6-phosphate (FIG. 1, step Z).

FIG. 1, Steps B and C—Hexulose-6-phosphate synthase (Step B) and 6-phospho-3-hexuloisomerase (Step C)

Both of the hexulose-6-phosphate synthase and 6-phospho-3-hexuloisomerase enzymes are found in several organisms, including methanotrophs and methylotrophs where they have been purified (Kato et al., 2006, Bio Sci Biotechnol Biochem. 70(1):10-21. In addition, these enzymes have been reported in heterotrophs such as Bacillus subtilis also where they are reported to be involved in formaldehyde detoxification (Mitsui et al., 2003, AEM 69(10):6128-32, Yasueda et al., 1999. J Bac 181(23):7154-60. Genes for these two enzymes from the methylotrophic bacterium Mycobacterium gastri MB19 have been fused and E. coli strains harboring the hps-phi construct showed more efficient utilization of formaldehyde (Orita et al., 2007, Appl Microbiol Biotechnol. 76:439-445). In some organisms, these two enzymes naturally exist as a fused version that is bifunctional.

Exemplary candidate genes for hexulose-6-phopshate synthase are:

GI

Protein
GenBank ID
number
Organism

Hps
AAR39392.1
40074227

Bacillus methanolicus MGA3

Hps
EIJ81375.1
387589055

Bacillus methanolicus PB1

RmpA
BAA83096.1
5706381

Methylomonas aminofaciens

RmpA
BAA90546.1
6899861

Mycobacterium gastri

YckG
BAA08980.1
1805418

Bacillus subtilis

Hps
YP_544362.1
91774606

Methylobacillus flagellatus

Hps
YP_545763.1
91776007

Methylobacillus flagellatus

Hps
AAG29505.1
11093955

Aminomonas aminovorus

SgbH
YP_004038706.1
313200048

Methylovorus sp. MP688

Hps
YP_003050044.1
253997981

Methylovorus glucosetrophus

SIP3-4

Hps
YP_003990382.1
312112066

Geobacillus sp. Y4.1MC1

Hps
gb|AAR91478.1
40795504

Geobacillus sp. M10EXG

Hps
YP_007402409.1
448238351

Geobacillus sp. GHH01

Exemplary gene candidates for 6-phospho-3-hexuloisomerase are:

Protein
GenBank ID
GI Number
Organism

Phi
AAR39393.1
40074228

Bacillus methanolicus MGA3

Phi
EIJ81376.1
387589056

Bacillus methanolicus PB1

Phi
BAA83098.1
5706383

Methylomonas aminofaciens

RmpB
BAA90545.1
6899860

Mycobacterium gastri

Phi
YP_545762.1
91776006

Methylobacillus flagellatus

KT

Phi
YP_003051269.1
253999206

Methylovorus glucosetrophus

Phi
YP_003990383.1
312112067

Geobacillus sp. Y4.1MC1

Phi
YP_007402408.1
448238350

Geobacillus sp. GHH01

Candidates for enzymes where both of these functions have been fused into a single open reading frame include the following.

Protein
GenBank ID
GI number
Organism

PH1938
NP_143767.1
14591680

Pyrococcus horikoshii OT3

PF0220
NP_577949.1
18976592

Pyrococcus furiosus

TK0475
YP_182888.1
57640410

Thermococcus

kodakaraensis

PAB1222
NP_127388.1
14521911

Pyrococcus abyssi

MCA2738
YP_115138.1
53803128

Methylococcus capsulatas

Metal_3152
EIC30826.1
380884949

Methylomicrobium album

FIG. 1, Step D—Dihydroxyacetone Synthase

The dihydroxyacetone synthase enzyme in Candida boidinii uses thiamine pyrophosphate and Mg²⁺as cofactors and is localized in the peroxisome. The enzyme from the methanol-growing carboxydobacterium, Mycobacter sp. strain JC1 DSM 3803, was also found to have DHA synthase and kinase activities (Ro et al., 1997, J Bac 179(19):6041-7). DHA synthase from this organism also has similar cofactor requirements as the enzyme from C. boidinii. The K_ms for formaldehyde and xylulose 5-phosphate were reported to be 1.86 mM and 33.3 microM, respectively. Several other mycobacteria, excluding only Mycobacterium tuberculosis, can use methanol as the sole source of carbon and energy and are reported to use dihydroxyacetone synthase (Part et al., 2003, J Bac 185(1):142-7.

Protein
GenBank ID
GI number
Organism

DAS1
AAC83349.1
3978466

Candida boidinii

HPODL_2613
EFW95760.1
320581540

Ogataea

parapolymorpha DL-1

(Hansenula polymorpha

DL-1)

AAG12171.2
18497328

Mycobacter sp. strain

JC1 DSM 3803

FIG. 1, Step Z—Fructose-6-phosphate Aldolase

Fructose-6-phosphate aldolase (F6P aldolase) can catalyze the combination of dihydroxyacetone (DHA) and glyceraldehyde-3-phosphate (G3P) to form fructose-6-phosphate. This activity was recently discovered in E. coli and the corresponding gene candidate has been termed fsa (Schurmann and Sprenger, J. Biol. Chem., 2001, 276(14), 11055-11061). The enzyme has narrow substrate specificity and cannot utilize fructose, fructose 1-phosphate, fructose 1,6-bisphosphate, or dihydroxyacetone phosphate. It can however use hydroxybutanone and acetol instead of DHA. The purified enzyme displayed a V_maxof 7 units/mg of protein for fructose 6-phosphate cleavage (at 30 degrees C., pH 8.5 in 50 mm glycylglycine buffer). For the aldolization reaction a V_maxof 45 units/mg of protein was found; K_mvalues for the substrates were 9 mM for fructose 6-phosphate, 35 mM for dihydroxyacetone, and 0.8 mM for glyceraldehyde 3-phosphate. The enzyme prefers the aldol formation over the cleavage reaction.

The selectivity of the E. coli enzyme towards DHA can be improved by introducing point mutations. For example, the mutation A129S improved reactivity towards DHA by over 17 fold in terms of Kcat/Km (Gutierrez et al., Chem Commun (Camb), 2011, 47(20), 5762-5764). The same mutation reduced the catalytic efficiency on hydroxyacetone by more than 3 fold and reduced the affinity for glycoaldehyde by more than 3 fold compared to that of the wild type enzyme (Castillo et al., Advanced Synthesis & Catalysis, 352(6), 1039-1046). Genes similar to fsa have been found in other genomes by sequence homology. Some exemplary gene candidates have been listed below.

Protein accession

Gene
no.
GI number
Organism

fsa
AAC73912.2
87081788

Escherichia coli K12

talC
AAC76928.1
1790382

Escherichia coli K12

fsa
WP_017209835.1
515777235

Clostridium beijerinckii

DR_1337
AAF10909.1
6459090

Deinococcus

radiodurans R1

talC
NP_213080.1
15605703

Aquifex aeolicus VF5

MJ_0960
NP_247955.1
15669150

Methanocaldococcus

janaschii

mipB
NP_993370.2
161511381

Yersinia pestis

As described below, there is an energetic advantage to using F6P aldolase in the DHA pathway. The assimilation of formaldehyde formed by the oxidation of methanol can proceed either via the dihydroxyacetone (DHA) pathway (step D, FIG. 1) or the Ribulose monophosphate (RuMP) pathway (steps B and C, FIG. 1). In the RuMP pathway, formaldehyde combines with ribulose-5-phosphate to form F6P. F6P is then either metabolized via glycolysis or used for regeneration of ribulose-5-phosphate to enable further formaldehyde assimilation. Notably, ATP hydrolysis is not required to form F6P from formaldehyde and ribulose-5-phosphate via the RuMP pathway.

In contrast, in the DHA pathway, formaldehyde combines with xylulose-5-phosphate (X5P) to form dihydroxyacetone (DHA) and glyceraldehyde-3-phosphate (G3P). Some of the DHA and G3P must be metabolized to F6P to enable regeneration of xylulose-5-phosphate. In the standard DHA pathway, DHA and G3P are converted to F6P by three enzymes: DHA kinase, fructose bisphosphate aldolase, and fructose bisphosphatase. The net conversion of DHA and G3P to F6P requires ATP hydrolysis as described below. First, DHA is phosphorylated to form DHA phosphate (DHAP) by DHA kinase at the expense of an ATP. DHAP and G3P are then combined by fructose bisphosphate aldolase to form fructose-1,6-diphosphate (FDP). FDP is converted to F6P by fructose bisphosphatase, thus wasting a high energy phosphate bond.

A more ATP efficient sequence of reactions is enabled if DHA synthase functions in combination with F6P aldolase as opposed to in combination with DHA kinase, fructose bisphosphate aldolase, and fructose bisphosphatase. F6P aldolase enables direct conversion of DHA and G3P to F6P, bypassing the need for ATP hydrolysis. Overall, DHA synthase when combined with F6P aldolase is identical in energy demand to the RuMP pathway. Both of these formaldehyde assimilation options (i.e., RuMP pathway, DHA synthase+F6P aldolase) are superior to DHA synthase combined with DHA kinase, fructose bisphosphate aldolase, and fructose bisphosphatase in terms of ATP demand.

Example VII
In Vivo Labeling Assay for Conversion of Methanol to CO₂

This example describes a functional methanol pathway in a microbial organism.

Strains with functional reductive TCA branch and pyruvate formate lyase deletion were grown aerobically in LB medium overnight, followed by inoculation of M9 high-seed media containing IPTG and aerobic growth for 4 hrs. These strains had methanol dehydrogenase/ACT pairs in the presence and absence of formaldehyde dehydrogenase or formate dehydrogenase. ACT is an activator protein (a Nudix hydrolase). At this time, strains were pelleted, resuspended in fresh M9 medium high-seed media containing 2% ¹³CH₃OH, and sealed in anaerobic vials. Head space was replaced with nitrogen and strains grown for 40 hours at 37° C. Following growth, headspace was analyzed for ¹³CO₂. Media was examined for residual methanol as well as 1,4-butanediol and byproducts. All constructs expressing methanol dehydrogenase (MeDH) mutants and MeDH/ACT pairs grew to slightly lower ODs than strains containing empty vector controls. This is likely due to the high expression of these constructs (Data not shown). One construct (2315/2317) displayed significant accumulation of labeled CO₂relative to controls in the presence of FalDH, FDH or no coexpressed protein. This shows a functional MeOH pathway in E. coli and that the endogenous glutathione-dependent formaldehyde detoxification genes (frmAB) are sufficient to carry flux generated by the current MeDH/ACT constructs.

2315 is internal laboratory designation for the MeDH from Bacillus methanolicus MGA3 (GenBank Accession number: EIJ77596.1; GI number: 387585261), and 2317 is internal laboratory designation for the activator protein from the same organism (locus tag: MGA3_09170; GenBank Accession number:EIJ83380; GI number: 387591061).

Sequence analysis of the NADH-dependent MeDH from Bacillus methanolicus places the enzyme in the alcohol dehydrogenase family III. It does not contain any tryptophan residues, resulting in a low extinction coefficient (18,500 M⁻¹, cm⁻¹) and should be detected on SDS gels by Coomassie staining.

The enzyme has been characterized as a multisubunit complex built from 43 kDa subunits containing one Zn and 1-2 Mg atoms per subunit. Electron microscopy and sedimentation studies determined it to be a decamer, in which two rings with five-fold symmetry are stacked on top of each other (Vonck et al., J. Biol. Chem. 266:3949-3954, 1991). It is described to contain a tightly but not covalently bound cofactor and requires exogenous NAD⁺ as e⁻-acceptor to measure activity in vitro. A strong increase (10-40-fold) of in vitro activity was observed in the presence of an activator protein (ACT), which is a homodimer (21 kDa subunits) and contains one Zn and one Mg atom per subunit.

The mechanism of the activation was investigated by Kloosterman et al., J. Biol. Chem. 277:34785-34792, 2002, showing that ACT is a Nudix hydrolase and Hektor et al., J. Biol. Chem. 277:46966-46973, 2002, demonstrating that mutation of residue S97 to G or T in MeDH changes activation characteristics along with the affinity for the cofactor. While mutation of residues G15 and D88 had no significant impact, a role of residue G13 for stability as well as of residues G95, D100, and K103 for the activity is suggested. Both papers together propose a hypothesis in which ACT cleaves MeDH-bound NAD⁺. MeDH retains AMP bound and enters an activated cycle with increased turnover.

The stoichiometric ratio between ACT and MeDH is not well defined in the literature. Kloosterman et al., supra determine the ratio of dimeric Act to decameric MeDH for full in vitro activation to be 10:1. In contrast, Arfman et al. J. Biol. Chem. 266:3955-3960, 1991 determined a ratio of 3:1 in vitro for maximum and a 1:6 ratio for significant activation, but observe a high sensitivity to dilution. Based on expression of both proteins in Bacillus, the authors estimate the ratio in vivo to be around 1:17.5.

However, our in vitro experiments with purified activator protein (2317A) and methanol dehydrogenase (2315A) showed the ratio of ACT to MeDH to be 10:1. This in vitro test was done with 5 M methanol, 2 mM NAD and 10 μM methanol dehydrogenase 2315A at pH 7.4.

Example VIII
Phosphoketolase-Dependent Acetyl-CoA Synthesis Enzymes

This Example provides genes that can be used for enhancing carbon flux through acetyl-CoA using phosphoketolase enzymes.

FIG. 1, Step T—Fructose-6-phosphate Phosphoketolase

Conversion of fructose-6-phosphate and phosphate to acetyl-phosphate and erythrose-5-phosphate can be carried out by fructose-6-phosphate phosphoketolase (EC 4.1.2.22). Conversion of fructose-6-phosphate and phosphate to acetyl-phosphate and erythrose-5-phosphate is one of the key reactions in the Bifidobacterium shunt. There is evidence for the existence of two distinct phosphoketolase enzymes in bifidobacteria (Sgorbati et al, 1976, Antonie Van Leeuwenhoek, 42(1-2) 49-57; Grill et al, 1995, Curr Microbiol, 31(1); 49-54). The enzyme from Bifidobacterium dentium appeared to be specific solely for fructose-6-phosphate (EC: 4.1.2.22) while the enzyme from Bifidobacterium pseudolongum subsp. globosum is able to utilize both fructose-6-phosphate and D-xylulose 5-phosphate (EC: 4.1.2.9) (Sgorbati et al, 1976, Antonie Van Leeuwenhoek, 42(1-2) 49-57). The enzyme encoded by the xfp gene, originally discovered in Bifidobacterium animalis lactis, is the dual-specificity enzyme (Meile et al., 2001, J Bacteriol, 183, 2929-2936; Yin et al, 2005, FEMS Microbiol Lett, 246(2); 251-257). Additional phosphoketolase enzymes can be found in Leuconostoc mesenteroides (Lee et al, Biotechnol Lett. 2005 June; 27(12):853-8), Clostridium acetobutylicum ATCC 824 (Servinsky et al, Journal of Industrial Microbiology & Biotechnology, 2012, 39, 1859-1867), Aspergillus nidulans (Kocharin et al, 2013, Biotechnol Bioeng, 110(8), 2216-2224; Papini, 2012, Appl Microbiol Biotechnol, 95 (4), 1001-1010), Bifidobacterium breve (Suziki et al, 2010, Acta Crystallogr Sect F Struct Biol Cryst Commun., 66(Pt 8):941-3), Lactobacillus paraplantarum (Jeong et al, 2007, J Microbiol Biotechnol, 17(5), 822-9).

GI

Protein
GENBANK ID
NUMBER
ORGANISM

xfp
YP_006280131.1
386867137

Bifidobacterium

animalis lactis

xfp
AAV66077.1
55818565

Leuconostoc

mesenteroides

CAC1343
NP_347971.1
15894622

Clostridium

acetobutylicum

ATCC 824

xpkA
CBF76492.1
259482219

Aspergillus nidulans

xfp
WP_003840380.1
489937073

Bifidobacterium dentium

ATCC 27678

xfp
AAR98788.1
41056827

Bifidobacterium

pseudolongum

subsp. globosum

xfp
WP_022857642.1
551237197

Bifidobacterium

pseudolongum

subsp. globosum

xfp
ADF97524.1
295314695

Bifidobacterium breve

xfp
AAQ64626.1
34333987

Lactobacillus

paraplantarum

FIG. 1, Step U—Xylulose-5-phosphate Phosphoketolase

Conversion of xylulose-5-phosphate and phosphate to acetyl-phosphate and glyceraldehyde-3-phosphate can be carried out by xylulose-5-phosphate phosphoketolase (EC 4.1.2.9). There is evidence for the existence of two distinct phosphoketolase enzymes in bifidobacteria (Sgorbati et al, 1976, Antonie Van Leeuwenhoek, 42(1-2) 49-57; Grill et al, 1995, Curr Microbiol, 31(1); 49-54). The enzyme from Bifidobacterium dentium appeared to be specific solely for fructose-6-phosphate (EC: 4.1.2.22) while the enzyme from Bifidobacterium pseudolongum subsp. globosum is able to utilize both fructose-6-phosphate and D-xylulose 5-phosphate (EC: 4.1.2.9) (Sgorbati et al, 1976, Antonie Van Leeuwenhoek, 42(1-2) 49-57). Many characterized enzymes have dual-specificity for xylulose-5-phosphate and fructose-6-phosphate. The enzyme encoded by the xfp gene, originally discovered in Bifidobacterium animalis lactis, is the dual-specificity enzyme (Meile et al., 2001, J Bacteriol, 183, 2929-2936; Yin et al, 2005, FEMS Microbiol Lett, 246(2); 251-257). Additional phosphoketolase enzymes can be found in Leuconostoc mesenteroides (Lee et al, Biotechnol Lett. 2005 June; 27(12):853-8), Clostridium acetobutylicum ATCC 824 (Servinsky et al, Journal of Industrial Microbiology & Biotechnology, 2012, 39, 1859-1867), Aspergillus nidulans (Kocharin et al, 2013, Biotechnol Bioeng, 110(8), 2216-2224; Papini, 2012, Appl Microbiol Biotechnol, 95 (4), 1001-1010), Bifidobacterium breve (Suziki et al, 2010, Acta Crystallogr Sect F Struct Biol Cryst Commun., 66(Pt 8):941-3), and Lactobacillus paraplantarum (Jeong et al, 2007, J Microbiol Biotechnol, 17(5), 822-9).

GI

Protein
GENBANK ID
NUMBER
ORGANISM

xfp
YP_006280131.1
386867137

Bifidobacterium

animalis lactis

xfp
AAV66077.1
55818565

Leuconostoc

mesenteroides

CAC1343
NP_347971.1
15894622

Clostridium

acetobutylicum

ATCC 824

xpkA
CBF76492.1
259482219

Aspergillus nidulans

xfp
AAR98788.1
41056827

Bifidobacterium

pseudolongum subsp.

globosum

xfp
WP_022857642.1
551237197

Bifidobacterium

pseudolongum

subsp. globosum

xfp
ADF97524.1
295314695

Bifidobacterium breve

xfp
AAQ64626.1
34333987

Lactobacillus

paraplantarum

FIG. 1, Step V—Phosphotransacetylase

The formation of acetyl-CoA from acetyl-phosphate can be catalyzed by phosphotransacetylase (EC 2.3.1.8). The pta gene from E. coli encodes an enzyme that reversibly converts acetyl-CoA into acetyl-phosphate (Suzuki, T., Biochim. Biophys. Acta 191:559-569 (969)). Additional acetyltransferase enzymes have been characterized in Bacillus subtilis (Rado and Hoch, Biochim. Biophys. Acta 321:114-125 (1973), Clostridium kluyveri (Stadtman, E., Methods Enzymol. 1:5896-599 (1955), and Thermotoga maritima (Bock et al., J. Bacteriol. 181:1861-1867 (1999)). This reaction can also be catalyzed by some phosphotransbutyrylase enzymes (EC 2.3.1.19), including the ptb gene products from Clostridium acetobutylicum (Wiesenborn et al., App. Environ. Microbiol. 55:317-322 (1989); Walter et al., Gene 134:107-111 (1993)). Additional ptb genes are found in butyrate-producing bacterium L2-50 (Louis et al., J. Bacteriol. 186:2099-2106 (2004) and Bacillus megaterium (Vazquez et al., Curr. Microbiol. 42:345-349 (2001). Homologs to the E. coli pta gene exist in several other organisms including Salmonella enterica and Chlamydomonas reinhardtii.

Protein
GenBank ID
GI Number
Organism

Pta
NP_416800.1
71152910

Escherichia coli

Pta
P39646
730415

Bacillus subtilis

Pta
A5N801
146346896

Clostridium kluyveri

Pta
Q9X0L4
6685776

Thermotoga maritime

Ptb
NP_349676
34540484

Clostridium acetobutylicum

Ptb
AAR19757.1
38425288
butyrate-producing

bacterium L2-50

Ptb
CAC07932.1
10046659

Bacillus megaterium

Pta
NP_461280.1
16765665

Salmonella enterica

subsp. enterica

serovar Typhimurium str. LT2

PAT2
XP_001694504.1
159472743

Chlamydomonas reinhardtii

PAT1
XP_001691787.1
159467202

Chlamydomonas reinhardtii

FIG. 1, Step W—Acetate Kinase

Acetate kinase (EC 2.7.2.1) can catalyze the reversible ATP-dependent phosphorylation of acetate to acetylphosphate. Exemplary acetate kinase enzymes have been characterized in many organisms including E. coli, Clostridium acetobutylicum and Methanosarcina thermophila (Ingram-Smith et al., J. Bacteriol. 187:2386-2394 (2005); Fox and Roseman, J. Biol. Chem. 261:13487-13497 (1986); Winzer et al., Microbioloy 143 (Pt 10):3279-3286 (1997)). Acetate kinase activity has also been demonstrated in the gene product of E. coli purT (Marolewski et al., Biochemistry 33:2531-2537 (1994). Some butyrate kinase enzymes (EC 2.7.2.7), for example buk1 and buk2 from Clostridium acetobutylicum, also accept acetate as a substrate (Hartmanis, M. G., J. Biol. Chem. 262:617-621 (1987)). Homologs exist in several other organisms including Salmonella enterica and Chlamydomonas reinhardtii.

Protein
GenBank ID
GI Number
Organism

ackA
NP_416799.1
16130231

Escherichia coli

Ack
AAB18301.1
1491790

Clostridium

acetobutylicum

Ack
AAA72042.1
349834

Methanosarcina

thermophila

purT
AAC74919.1
1788155

Escherichia coli

buk1
NP_349675
15896326

Clostridium

acetobutylicum

buk2
Q97II1
20137415

Clostridium

acetobutylicum

ackA
NP_461279.1
16765664

Salmonella typhimurium

ACK1
XP_001694505.1
159472745

Chlamydomonas

reinhardtii

ACK2
XP_001691682.1
159466992

Chlamydomonas

reinhardtii

FIG. 1, Step X—Acetyl-CoA Transferase, Synthetase, or Ligase

The acylation of acetate to acetyl-CoA can be catalyzed by enzymes with acetyl-CoA synthetase, ligase or transferase activity. Two enzymes that can catalyze this reaction are AMP-forming acetyl-CoA synthetase or ligase (EC 6.2.1.1) and ADP-forming acetyl-CoA synthetase (EC 6.2.1.13). AMP-forming acetyl-CoA synthetase (ACS) is the predominant enzyme for activation of acetate to acetyl-CoA. Exemplary ACS enzymes are found in E. coli (Brown et al., J. Gen. Microbiol. 102:327-336 (1977)), Ralstonia eutropha (Priefert and Steinbuchel, J. Bacteriol. 174:6590-6599 (1992)), Methanothermobacter thermautotrophicus (Ingram-Smith and Smith, Archaea 2:95-107 (2007)), Salmonella enterica (Gulick et al., Biochemistry 42:2866-2873 (2003)) and Saccharomyces cerevisiae (Jogl and Tong, Biochemistry 43:1425-1431 (2004)). ADP-forming acetyl-CoA synthetases are reversible enzymes with a generally broad substrate range (Musfeldt and Schonheit, J. Bacteriol. 184:636-644 (2002)). Two isozymes of ADP-forming acetyl-CoA synthetases are encoded in the Archaeoglobus fulgidus genome by are encoded by AF1211 and AF1983 (Musfeldt and Schonheit, supra (2002)). The enzyme from Haloarcula marismortui (annotated as a succinyl-CoA synthetase) also accepts acetate as a substrate and reversibility of the enzyme was demonstrated (Brasen and Schonheit, Arch. Microbiol. 182:277-287 (2004)). The ACD encoded by PAE3250 from hyperthermophilic crenarchaeon Pyrobaculum aerophilum showed the broadest substrate range of all characterized ACDs, reacting with acetate, isobutyryl-CoA (preferred substrate) and phenylacetyl-CoA (Brasen and Schonheit, supra (2004)). Directed evolution or engineering can be used to modify this enzyme to operate at the physiological temperature of the host organism. The enzymes from A. fulgidus, H. marismortui and P. aerophilum have all been cloned, functionally expressed, and characterized in E. coli (Brasen and Schonheit, supra (2004); Musfeldt and Schonheit, supra (2002)). Additional candidates include the succinyl-CoA synthetase encoded by sucCD in E. coli (Buck et al., Biochemistry 24:6245-6252 (1985)) and the acyl-CoA ligase from Pseudomonas putida (Fernandez-Valverde et al., Appl. Environ. Microbiol. 59:1149-1154 (1993)). The aforementioned proteins are shown below.

Protein
GenBank ID
GI Number
Organism

Acs
AAC77039.1
1790505

Escherichia coli

acoE
AAA21945.1
141890

Ralstonia eutropha

acs1
ABC87079.1
86169671

Methanothermobacter

thermautotrophicus

acs1
AAL23099.1
16422835

Salmonella enterica

ACS1
Q01574.2
257050994

Saccharomyces cerevisiae

AF1211
NP_070039.1
11498810

Archaeoglobus fulgidus

AF1983
NP_070807.1
11499565

Archaeoglobus fulgidus

Scs
YP_135572.1
55377722

Haloarcula marismortui

PAE3250
NP_560604.1
18313937

Pyrobaculum aerophilum

str. IM2

sucC
NP_415256.1
16128703

Escherichia coli

sucD
AAC73823.1
1786949

Escherichia coli

paaF
AAC24333.2
22711873

Pseudomonas putida

An acetyl-CoA transferase that can utilize acetate as the CoA acceptor is acetoacetyl-CoA transferase, encoded by the E. coli atoA (alpha subunit) and atoD (beta subunit) genes (Vanderwinkel et al., Biochem. Biophys. Res Commun. 33:902-908 (1968); Korolev et al., Acta Crystallogr. D Biol Crystallogr. 58:2116-2121 (2002)). This enzyme has also been shown to transfer the CoA moiety to acetate from a variety of branched and linear acyl-CoA substrates, including isobutyrate (Matthies et al., Appl Environ Microbiol 58:1435-1439 (1992)), valerate (Vanderwinkel et al., supra) and butanoate (Vanderwinkel et al., supra). Similar enzymes exist in Corynebacterium glutamicum ATCC 13032 (Duncan et al., Appl Environ Microbiol 68:5186-5190 (2002)), Clostridium acetobutylicum (Cary et al., Appl Environ Microbiol 56:1576-1583 (1990)), and Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci. Biotechnol Biochem. 71:58-68 (2007)). These proteins are identified below.

Protein
GenBank ID
GI Number
Organism

atoA
P76459.1
2492994

Escherichia coli K12

atoD
P76458.1
2492990

Escherichia coli K12

actA
YP_226809.1
62391407

Corynebacterium glutamicum

ATCC 13032

cg0592
YP_224801.1
62389399

Corynebacterium glutamicum

ATCC 13032

ctfA
NP_149326.1
15004866

Clostridium acetobutylicum

ctfB
NP_149327.1
15004867

Clostridium acetobutylicum

ctfA
AAP42564.1
31075384

Clostridium

saccharoperbutylacetonicum

ctfB
AAP42565.1
31075385

Clostridium

saccharoperbutylacetonicum

Additional exemplary acetyl-CoA transferase candidates are catalyzed by the gene products of cat1, cat2, and cat3 of Clostridium kluyveri which have been shown to exhibit succinyl-CoA, 4-hydroxybutyryl-CoA, and butyryl-CoA transferase activity, respectively (Seedorf et al., supra; Sohling et al., Eur. J Biochem. 212:121-127 (1993); Sohling et al., J Bacteriol. 178:871-880 (1996)). Similar CoA transferase activities are also present in Trichomonas vaginalis (van Grinsven et al., J. Biol. Chem. 283:1411-1418 (2008)) and Trypanosoma brucei (Riviere et al., J. Biol. Chem. 279:45337-45346 (2004)). These proteins are identified below.

Protein
GenBank ID
GI Number
Organism

cat1
P38946.1
729048

Clostridium kluyveri

cat2
P38942.2
172046066

Clostridium kluyveri

cat3
EDK35586.1
146349050

Clostridium kluyveri

TVAG_395550
XP_001330176
123975034

Trichomonas

vaginalis G3

Tb11.02.0290
XP_828352
71754875

Trypanosoma brucei

Example IX
Acetyl-CoA, Oxaloacetate and Succinyl-CoA Synthesis Enzymes

This Example provides genes that can be used for conversion of glycolysis intermediate glyceraldehyde-3-phosphate (G3P) to acetyl-CoA and/or succinyl-CoA as depicted in the pathways of FIG. 4.

A. PEP Carboxylase or PEP Carboxykinase.

Carboxylation of phosphoenolpyruvate to oxaloacetate is catalyzed by phosphoenolpyruvate carboxylase. Exemplary PEP carboxylase enzymes are encoded by ppc in E. coli (Kai et al., Arch. Biochem. Biophys. 414:170-179 (2003), ppcA in Methylobacterium extorquens AM1 (Arps et al., J. Bacteriol. 175:3776-3783 (1993), and ppc in Corynebacterium glutamicum (Eikmanns et al., Mol. Gen. Genet. 218:330-339 (1989).

Protein
GenBank ID
GI Number
Organism

Ppc
NP_418391
16131794

Escherichia coli

ppcA
AAB58883
28572162

Methylobacterium

extorquens

Ppc
ABB53270
80973080

Corynebacterium

glutamicum

An alternative enzyme for converting phosphoenolpyruvate to oxaloacetate is PEP carboxykinase, which simultaneously forms an ATP while carboxylating PEP. In most organisms PEP carboxykinase serves a gluconeogenic function and converts oxaloacetate to PEP at the expense of one ATP. S. cerevisiae is one such organism whose native PEP carboxykinase, PCK1, serves a gluconeogenic role (Valdes-Hevia et al., FEBS Lett. 258:313-316 (1989). E. coli is another such organism, as the role of PEP carboxykinase in producing oxaloacetate is believed to be minor when compared to PEP carboxylase, which does not form ATP, possibly due to the higher K_mfor bicarbonate of PEP carboxykinase (Kim et al., Appl. Environ. Microbiol. 70:1238-1241 (2004)). Nevertheless, activity of the native E. coli PEP carboxykinase from PEP towards oxaloacetate has been recently demonstrated in ppc mutants of E. coli K-12 (Kwon et al., J. Microbiol. Biotechnol. 16:1448-1452 (2006)). These strains exhibited no growth defects and had increased succinate production at high NaHCO₃concentrations. Mutant strains of E. coli can adopt Pck as the dominant CO2-fixing enzyme following adaptive evolution (Zhang et al. 2009). In some organisms, particularly rumen bacteria, PEP carboxykinase is quite efficient in producing oxaloacetate from PEP and generating ATP. Examples of PEP carboxykinase genes that have been cloned into E. coli include those from Mannheimia succiniciproducens (Lee et al., Biotechnol. Bioprocess Eng. 7:95-99 (2002)), Anaerobiospirillum succiniciproducens (Laivenieks et al., Appl. Environ. Microbiol. 63:2273-2280 (1997), and Actinobacillus succinogenes (Kim et al. supra). The PEP carboxykinase enzyme encoded by Haemophilus influenza is effective at forming oxaloacetate from PEP.

Protein
GenBank ID
GI Number
Organism

PCK1
NP_013023
6322950

Saccharomyces cerevisiae

pck
NP_417862.1
16131280

Escherichia coli

pckA
YP_089485.1
52426348

Mannheimia succiniciproducens

pckA
O09460.1
3122621

Anaerobiospirillum

succiniciproducens

pckA
Q6W6X5
75440571

Actinobacillus succinogenes

pckA
P43923.1
1172573

Haemophilus influenza

B. Malate Dehydrogenase.

Oxaloacetate is converted into malate by malate dehydrogenase (EC 1.1.1.37), an enzyme which functions in both the forward and reverse direction. S. cerevisiae possesses three copies of malate dehydrogenase, MDH1 (McAlister-Henn and Thompson, J. Bacteriol. 169:5157-5166 (1987), MDH2 (Minard and McAlister-Henn, Mol. Cell. Biol. 11:370-380 (1991); Gibson and McAlister-Henn, J. Biol. Chem. 278:25628-25636 (2003)), and MDH3 (Steffan and McAlister-Henn, J. Biol. Chem. 267:24708-24715 (1992)), which localize to the mitochondrion, cytosol, and peroxisome, respectively. E. coli is known to have an active malate dehydrogenase encoded by mdh.

Protein
GenBank ID
GI Number
Organism

MDH1
NP_012838
6322765

Saccharomyces cerevisiae

MDH2
NP_014515
116006499

Saccharomyces cerevisiae

MDH3
NP_010205
6320125

Saccharomyces cerevisiae

Mdh
NP_417703.1
16131126

Escherichia coli

C. Fumarase.

Fumarate hydratase (EC 4.2.1.2) catalyzes the reversible hydration of fumarate to malate. The three fumarases of E. coli, encoded by fumA, fumB and fumC, are regulated under different conditions of oxygen availability. FumB is oxygen sensitive and is active under anaerobic conditions. FumA is active under microanaerobic conditions, and FumC is active under aerobic growth conditions (Tseng et al., J. Bacteriol. 183:461-467 (2001); Woods et al., Biochim. Biophys. Acta 954:14-26 (1988); Guest et al., J. Gen. Microbiol. 131:2971-2984 (1985)). S. cerevisiae contains one copy of a fumarase-encoding gene, FUM1, whose product localizes to both the cytosol and mitochondrion (Sass et al., J. Biol. Chem. 278:45109-45116 (2003)). Additional fumarase enzymes are found in Campylobacter jejuni (Smith et al., Int. J. Biochem. Cell. Biol. 31:961-975 (1999)), Thermus thermophilus (Mizobata et al., Arch. Biochem. Biophys. 355:49-55 (1998)) and Rattus norvegicus (Kobayashi et al., J. Biochem. 89:1923-1931 (1981)). Similar enzymes with high sequence homology include fum1 from Arabidopsis thaliana and fumC from Corynebacterium glutamicum. The MmcBC fumarase from Pelotomaculum thermopropionicum is another class of fumarase with two subunits (Shimoyama et al., FEMS Microbiol. Lett. 270:207-213 (2007)).

Protein
GenBank ID
GI Number
Organism

fumA
NP_416129.1
16129570

Escherichia coli

fumB
NP_418546.1
16131948

Escherichia coli

fumC
NP_416128.1
16129569

Escherichia coli

FUM1
NP_015061
6324993

Saccharomyces cerevisiae

fumC
Q8NRN8.1
39931596

Corynebacterium glutamicum

fumC
O69294.1
9789756

Campylobacter jejuni

fumC
P84127
75427690

Thermus thermophilus

fumH
P14408.1
120605

Rattus norvegicus

MmcB
YP_001211906
147677691

Pelotomaculum

thermopropionicum

MmcC
YP_001211907
147677692

Pelotomaculum

thermopropionicum

D. Fumarate Reductase.

Fumarate reductase catalyzes the reduction of fumarate to succinate. The fumarate reductase of E. coli, composed of four subunits encoded by frdABCD, is membrane-bound and active under anaerobic conditions. The electron donor for this reaction is menaquinone and the two protons produced in this reaction do not contribute to the proton gradient (Iverson et al., Science 284:1961-1966 (1999)). The yeast genome encodes two soluble fumarate reductase isozymes encoded by FRDS1 (Enomoto et al., DNA Res. 3:263-267 (1996)) and FRDS2 (Muratsubaki et al., Arch. Biochem. Biophys. 352:175-181 (1998)), which localize to the cytosol and promitochondrion, respectively, and are used during anaerobic growth on glucose (Arikawa et al., FEMS Microbiol. Lett. 165:111-116 (1998)).

Protein
GenBank ID
GI Number
Organism

FRDS1
P32614
418423

Saccharomyces cerevisiae

FRDS2
NP_012585
6322511

Saccharomyces cerevisiae

frdA
NP_418578.1
16131979

Escherichia coli

frdB
NP_418577.1
16131978

Escherichia coli

frdC
NP_418576.1
16131977

Escherichia coli

frdD
NP_418475.1
16131877

Escherichia coli

E. Succinyl-CoA Synthetase or Transferase.

The ATP-dependent acylation of succinate to succinyl-CoA is catalyzed by succinyl-CoA synthetase (EC 6.2.1.5). The product of the LSC1 and LSC2 genes of S. cerevisiae and the sucC and sucD genes of E. coli naturally form a succinyl-CoA synthetase complex that catalyzes the formation of succinyl-CoA from succinate with the concomitant consumption of one ATP, a reaction which is reversible in vivo (Buck et al., Biochemistry 24:6245-6252 (1985)). These proteins are identified below:

Protein
GenBank ID
GI Number
Organism

LSC1
NP_014785
6324716

Saccharomyces cerevisiae

LSC2
NP_011760
6321683

Saccharomyces cerevisiae

sucC
NP_415256.1
16128703

Escherichia coli

sucD
AAC73823.1
1786949

Escherichia coli

Succinyl-CoA transferase converts succinate and an acyl-CoA donor to succinyl-CoA and an acid. Succinyl-CoA transferase enzymes include ygfH of E. coli and cat1 of Clostridium kluyveri (Seedorf et al., Proc. Natl. Acad. Sci U.S.A. 105:2128-2133 (2008); Sohling et al., J Bacteriol. 178:871-880 (1996); Haller et al., Biochemistry, 39(16) 4622-4629). Homologs can be found in, for example, Citrobacter youngae ATCC 29220, Salmonella enterica subsp. arizonae serovar, and Yersinia intermedia ATCC 29909. Succinyl-CoA transferase enzymes are encoded by pcaI and pcaJ in Pseudomonas putida (Kaschabek et al., J Bacteriol. 184:207-215 (2002)). Similar enzymes are found in Acinetobacter sp. ADP1 (Kowalchuk et al., Gene 146:23-30 (1994)), Streptomyces coelicolor and Pseudomonas knackmussii (formerly sp. B13) (Gobel et al., J Bacteriol. 184:216-223 (2002); Kaschabek et al., J Bacteriol. 184:207-215 (2002)). Additional exemplary succinyl-CoA transferases have been characterized in Helicobacter pylori (Corthesy-Theulaz et al., J Biol. Chem. 272:25659-25667 (1997)), Bacillus subtilis (Stols et al., Protein Expr. Purif. 53:396-403 (2007)) and Homo sapiens (Fukao, T., et al., Genomics 68:144-151 (2000); Tanaka, H., et al., Mol Hum Reprod 8:16-23 (2002)). Additional CoA transferases, described herein, are also suitable candidates.

Gene
GI #
Accession No.
Organism

ygfH
AAC75957.1
1789287

Escherichia coli

cat1
P38946.1
729048

Clostridium

kluyveri

CIT292_04485
ZP_03838384.1
227334728

Citrobacter

youngae

SARI_04582
YP_001573497.1
161506385

Salmonella

enterica

yinte0001_14430
ZP_04635364.1
238791727

Yersinia

intermedia

pcaI
24985644
AAN69545.1

Pseudomonas

putida

pcaJ
26990657
NP_746082.1

Pseudomonas

putida

pcaI
50084858
YP_046368.1

Acinetobacter

sp. ADP1

pcaJ
141776
AAC37147.1

Acinetobacter

sp. ADP1

pcaI
21224997
NP_630776.1

Streptomyces

coelicolor

pcaJ
21224996
NP_630775.1

Streptomyces

coelicolor

catI
75404583
Q8VPF3

Pseudomonas

knackmussii

catJ
75404582
Q8VPF2

Pseudomonas

knackmussii

HPAG1_0676
108563101
YP_627417

Helicobacter

pylori

HPAG1_0677
108563102
YP_627418

Helicobacter

pylori

ScoA
16080950
NP_391778

Bacillus

subtilis

ScoB
16080949
NP_391777

Bacillus

subtilis

OXCT1
NP_000427
4557817

Homo sapiens

OXCT2
NP_071403
11545841

Homo sapiens

F. Pyruvate Kinase or PTS-Dependent Substrate Import.

See elsewhere herein.

G. Pyruvate Dehydrogenase, Pyruvate Formate Lyase or Pyruvate:Ferredoxin Oxidoreductase.

Pyruvate:ferredoxin oxidoreductase (PFOR) catalyzes the reversible oxidation of pyruvate to form acetyl-CoA. Exemplary PFOR enzymes are found in Desulfovibrio africanus (Pieulle et al., J. Bacteriol. 179:5684-5692 (1997)) and other Desulfovibrio species (Vita et al., Biochemistry, 47: 957-64 (2008)). The M. thermoacetica PFOR is also well characterized (Menon and Ragsdale, Biochemistry 36:8484-8494 (1997)) and was shown to have high activity in the direction of pyruvate synthesis during autotrophic growth (Furdui and Ragsdale, J. Biol. Chem. 275:28494-28499 (2000)). Further, E. coli possesses an uncharacterized open reading frame, ydbK, encoding a protein that is 51% identical to the M. thermoacetica PFOR. Evidence for pyruvate oxidoreductase activity in E. coli has been described (Blaschkowski et al., Eur. J. Biochem. 123:563-569 (1982)). Finally, flavodoxin reductases (e.g., fqrB from Helicobacter pylori or Campylobacter jejuni) (St Maurice et al., J. Bacteriol. 189:4764-4773 (2007)) or Rnf-type proteins (Seedorf et al., Proc. Natl. Acad. Sci. U.S.A. 105:2128-2133 (2008); and Herrmann, J. Bacteriol 190:784-791 (2008)) provide a means to generate NADH or NADPH from the reduced ferredoxin generated by PFOR.

GI

Protein
GenBank ID
Number
Organism

DesfrDRAFT_0121
ZP_07331646.1
303245362

Desulfovibrio

fructosovorans

JJ

Por
CAA70873.1
1770208

Desulfovibrio

africanus

por
YP_012236.1
46581428

Desulfovibrio

vulgaris str.

Hildenborough

Dde_3237
ABB40031.1
78220682

DesulfoVibrio

desulfuricans

G20

Ddes_0298
YP_002478891.1
220903579

Desulfovibrio

desulfuricans

subsp.

desulfuricans

str. ATCC 27774

Por
YP_428946.1
83588937

Moorella

thermoacetica

YdbK
NP_415896.1
16129339

Escherichia

coli

The conversion of pyruvate into acetyl-CoA can be catalyzed by several other enzymes or their combinations thereof. For example, pyruvate dehydrogenase can transform pyruvate into acetyl-CoA with the concomitant reduction of a molecule of NAD into NADH. It is a multi-enzyme complex that catalyzes a series of partial reactions which results in acylating oxidative decarboxylation of pyruvate. The enzyme comprises of three subunits: pyruvate decarboxylase (E1), dihydrolipoamide acyltransferase (E2) and dihydrolipoamide dehydrogenase (E3). This enzyme is naturally present in several organisms, including E. coli and S. cerevisiae. In the E. coli enzyme, specific residues in the E1 component are responsible for substrate specificity (Bisswanger, H., J. Biol. Chem. 256:815-82 (1981); Bremer, J., Eur. J. Biochem. 8:535-540 (1969); Gong et al., J. Biol. Chem. 275:13645-13653 (2000)). Enzyme engineering efforts have improved the E. coli PDH enzyme activity under anaerobic conditions (Kim et al., J. Bacteriol. 190:3851-3858 (2008); Kim et al., Appl. Environ. Microbiol. 73:1766-1771 (2007); Zhou et al., Biotechnol. Lett. 30:335-342 (2008)). In contrast to the E. coli PDH, the B. subtilis complex is active and required for growth under anaerobic conditions (Nakano et al., J. Bacteriol. 179:6749-6755 (1997)). The Klebsiella pneumoniae PDH, characterized during growth on glycerol, is also active under anaerobic conditions (5).

Gene
Accession No.
GI #
Organism

aceE
NP_414656.1
16128107

Escherichia coli

aceF
NP_414657.1
16128108

Escherichia coli

lpd
NP_414658.1
16128109

Escherichia coli

pdhA
P21881.1
3123238

Bacillus subtilis

pdhB
P21882.1
129068

Bacillus subtilis

pdhC
P21883.2
129054

Bacillus subtilis

pdhD
P21880.1
118672

Bacillus subtilis

LAT1
NP_014328
6324258

Saccharomyces cerevisiae

PDA1
NP_011105
37362644

Saccharomyces cerevisiae

PDB1
NP_009780
6319698

Saccharomyces cerevisiae

LPD1
NP_116635
14318501

Saccharomyces cerevisiae

PDX1
NP_011709
6321632

Saccharomyces cerevisiae

Yet another enzyme that can catalyze this conversion is pyruvate formate lyase. This enzyme catalyzes the conversion of pyruvate and CoA into acetyl-CoA and formate. Pyruvate formate lyase is a common enzyme in prokaryotic organisms that is used to help modulate anaerobic redox balance. Exemplary enzymes can be found in Escherichia coli encoded by pflB (Knappe and Sawers, FEMS. Microbiol Rev. 6:383-398 (1990)), Lactococcus lactis (Melchiorsen et al., Appl Microbiol Biotechnol 58:338-344 (2002)), and Streptococcus mutans (Takahashi-Abbe et al., Oral. Microbiol Immunol. 18:293-297 (2003)). E. coli possesses an additional pyruvate formate lyase, encoded by tdcE, that catalyzes the conversion of pyruvate or 2-oxobutanoate to acetyl-CoA or propionyl-CoA, respectively (Hesslinger et al., Mol. Microbiol 27:477-492 (1998)). Both pflB and tdcE from E. coli require the presence of pyruvate formate lyase activating enzyme, encoded by pflA. Further, a short protein encoded by yfiD in E. coli can associate with and restore activity to oxygen-cleaved pyruvate formate lyase (Vey et al., Proc. Natl. Acad. Sci. U.S.A. 105:16137-16141 (2008). Note that pflA and pflB from E. coli were expressed in S. cerevisiae as a means to increase cytosolic acetyl-CoA for butanol production as described in WO/2008/080124]. Additional pyruvate formate lyase and activating enzyme candidates, encoded by pfl and act, respectively, are found in Clostridium pasteurianum (Weidner et al., J Bacteriol. 178:2440-2444 (1996)).

Protein
GenBank ID
GI Number
Organism

pflB
NP_415423
16128870

Escherichia coli

pflA
NP_415422.1
16128869

Escherichia coli

tdcE
AAT48170.1
48994926

Escherichia coli

yfiD
AAC75632.1
1788933

Escherichia coli

pfl
Q46266.1
2500058

Clostridium pasteurianum

act
CAA63749.1
1072362

Clostridium pasteurianum

Further, different enzymes can be used in combination to convert pyruvate into acetyl-CoA in multiple steps. For example, in S. cerevisiae, acetyl-CoA is obtained in the cytosol by first decarboxylating pyruvate to form acetaldehyde; the latter is oxidized to acetate by acetaldehyde dehydrogenase and subsequently activated to form acetyl-CoA by acetyl-CoA synthetase. Acetyl-CoA synthetase is a native enzyme in several other organisms including E. coli (Kumari et al., J. Bacteriol. 177:2878-2886 (1995)), Salmonella enterica (Starai et al., Microbiology 151:3793-3801 (2005); Starai et al., J. Biol. Chem. 280:26200-26205 (2005)), and Moorella thermoacetica (described already). Alternatively, acetate can be activated to form acetyl-CoA by acetate kinase and phosphotransacetylase. Acetate kinase first converts acetate into acetyl-phosphate with the accompanying use of an ATP molecule. Acetyl-phosphate and CoA are next converted into acetyl-CoA with the release of one phosphate by phosphotransacetylase. Exemplary enzymes encoding acetate kinase, acetyl-CoA synthetase and phosphotransacetlyase are described above.

Yet another way of converting pyruvate to acetyl-CoA is via pyruvate oxidase. Pyruvate oxidase converts pyruvate into acetate, using ubiquinone as the electron acceptor. In E. coli, this activity is encoded by poxB. PoxB has similarity to pyruvate decarboxylase of S. cerevisiae and Zymomonas mobilis. The enzyme has a thiamin pyrophosphate cofactor (Koland and Gennis, Biochemistry 21:4438-4442 (1982)); O'Brien et al., Biochemistry 16:3105-3109 (1977); O'Brien and Gennis, J. Biol. Chem. 255:3302-3307 (1980)) and a flavin adenine dinucleotide (FAD) cofactor. Acetate can then be converted into acetyl-CoA by either acetyl-CoA synthetase or by acetate kinase and phosphotransacetylase, as described earlier. Some of these enzymes can also catalyze the reverse reaction from acetyl-CoA to pyruvate.

H. Citrate Synthase.

Citrate synthases are well known in the art. For example, the gltA gene of E. coli encodes for a citrate synthase. It was previously shown that this gene is inhibited allosterically by NADH, and the amino acids involved in this inhibition have been identified (Pereira et al., J. Biol. Chem. 269(1):412-417 (1994); Stokell et al., J. Biol. Chem. 278(37):35435-35443 (2003)). An NADH insensitive citrate synthase can be encoded by gltA, such as an R163L mutant of gltA. Other citrate synthase enzymes are less sensitive to NADH, including the aarA enzyme of Acetobacter aceti (Francois et al, Biochem 45:13487-99 (2006)).

Protein
GenBank ID
GI number
Organism

gltA
NP_415248.1
16128695

Escherichia coli

AarA
P20901.1
116462

Acetobacter aceti

CIT1
NP_014398.1
6324328

Saccharomyces cerevisiae

CS
NP_999441.1
47523618

Sus scrofa

I. Aconitase.

Aconitase (EC 4.2.1.3) is an iron-sulfur-containing protein catalyzing the reversible isomerization of citrate and iso-citrate via the intermediate cis-aconitate. Two aconitase enzymes of E. coli are encoded by acnA and acnB. AcnB is the main catabolic enzyme, while AcnA is more stable and appears to be active under conditions of oxidative or acid stress (Cunningham et al., Microbiology 143 (Pt 12):3795-3805 (1997)). Two isozymes of aconitase in Salmonella typhimurium are encoded by acnA and acnB (Horswill and Escalante-Semerena, Biochemistry 40:4703-4713 (2001)). The S. cerevisiae aconitase, encoded by ACO1, is localized to the mitochondria where it participates in the TCA cycle (Gangloff et al., Mol. Cell. Biol. 10:3551-3561 (1990)) and the cytosol where it participates in the glyoxylate shunt (Regev-Rudzki et al., Mol. Biol. Cell. 16:4163-4171 (2005)).

Protein
GenBank ID
GI Number
Organism

acnA
AAC7438.1
1787531

Escherichia coli

acnB
AAC73229.1
2367097

Escherichia coli

HP0779
NP_207572.1
15645398

Helicobacter pylori

26695

H16_B0568
CAJ95365.1
113529018

Ralstonia eutropha

DesfrDRAFT_3783
ZP_07335307.1
303249064

Desulfovibrio

fructosovorans JJ

Suden_1040
ABB44318.1
78497778

Sulfurimonas

(acnB)

denitrificans

Hydth_0755
ADO45152.1
308751669

Hydrogenobacter

thermophilus

CT0543 (acn)
AAM71785.1
21646475

Chlorobium tepidum

Clim_2436
YP_001944436.1
189347907

Chlorobium limicola

Clim_0515
ACD89607.1
189340204

Chlorobium limicola

acnA
NP_460671.1
16765056

Salmonella

typhimurium

acnB
NP_459163.1
16763548

Salmonella

typhimurium

ACO1
AAA34389.1
170982

Saccharomyces

cerevisiae

J. Isocitrate Dehydrogenase.

Isocitrate dehydrogenase catalyzes the decarboxylation of isocitrate to 2-oxoglutarate coupled to the reduction of NAD(P)⁺. IDH enzymes in Saccharomyces cerevisiae and Escherichia coli are encoded by IDP1 and icd, respectively (Haselbeck and McAlister-Henn, J. Biol. Chem. 266:2339-2345 (1991); Nimmo, H. G., Biochem. J. 234:317-2332 (1986)). The reverse reaction in the reductive TCA cycle, the reductive carboxylation of 2-oxoglutarate to isocitrate, is favored by the NADPH-dependent CO₂-fixing IDH from Chlorobium limicola (Kanao et al., Eur. J. Biochem. 269:1926-1931 (2002)). A similar enzyme with 95% sequence identity is found in the C. tepidum genome in addition to some other candidates listed below.

Protein
GenBank ID
GI Number
Organism

Icd
ACI84720.1
209772816

Escherichia coli

IDP1
AAA34703.1
171749

Saccharomyces cerevisiae

Idh
BAC00856.1
21396513

Chlorobium limicola

Icd
AAM71597.1
21646271

Chlorobium tepidum

icd
NP_952516.1
39996565

Geobacter sulfurreducens

icd
YP_393560.
78777245

Sulfurimonas denitrificans

K. AKG Dehydrogenase.

Alpha-ketoglutarate dehydrogenase (AKGD) converts alpha-ketoglutarate to succinyl-CoA and is the primary site of control of metabolic flux through the TCA cycle (Hansford, Curr. Top. Bioenerg. 10:217-278 (1980)). Encoded by genes sucA, sucB and lpd in E. coli, AKGD gene expression is downregulated under anaerobic conditions and during growth on glucose (Park et al., Mol Micro 15:473-482 (1995)). Other exemplary AKGDH enzymes are found in organisms such as Bacillus subtilis and S. cerevisiae (Resnekov et al., Mol. Gen. Genet. 234:285-296 (1992); Repetto et al., Mol. Cell Biol. 9:2695-2705 (1989)).

Gene
GI #
Accession No.
Organism

sucA
16128701
NP_415254.1

Escherichia coli

sucB
16128702
NP_415255.1

Escherichia coli

lpd
16128109
NP_414658.1

Escherichia coli

odhA
51704265
P23129.2

Bacillus subtilis

odhB
129041
P16263.1

Bacillus subtilis

pdhD
118672
P21880.1

Bacillus subtilis

KGD1
6322066
NP_012141.1

Saccharomyces cerevisiae

KGD2
6320352
NP_010432.1

Saccharomyces cerevisiae

LPD1
14318501
NP_116635.1

Saccharomyces cerevisiae

The conversion of alpha-ketoglutarate to succinyl-CoA can also be catalyzed by alpha-ketoglutarate:ferredoxin oxidoreductase (EC 1.2.7.3), also known as 2-oxoglutarate synthase or 2-oxoglutarate:ferredoxin oxidoreductase (OFOR). OFOR and pyruvate:ferredoxin oxidoreductase (PFOR) are members of a diverse family of 2-oxoacid:ferredoxin (flavodoxin) oxidoreductases which utilize thiamine pyrophosphate, CoA and iron-sulfur clusters as cofactors and ferredoxin, flavodoxin and FAD as electron carriers (Adams et al., Archaea. Adv. Protein Chem. 48:101-180 (1996)). Exemplary OFOR enzymes are found in organisms such as Hydrogenobacter thermophilus, Desulfobacter hydrogenophilus and Chlorobium species (Shiba et al. 1985; Evans et al., Proc. Natl. Acad. ScI. U.S.A. 55:92934 (1966); Buchanan, 1971). The two-subunit enzyme from H. thermophilus, encoded by korAB, has been cloned and expressed in E. coli (Yun et al., Biochem. Biophys. Res. Commun. 282:589-594 (2001)). A five subunit OFOR from the same organism with strict substrate specificity for succinyl-CoA, encoded by forDABGE, was recently identified and expressed in E. coli (Yun et al. Biochem. Biophys. Res. Commun. 292:280-286 (2002)). Another exemplary OFOR is encoded by oorDABC in Helicobacter pylori (Hughes et al., J. Bacteriol. 180:1119-1128 (1998)). An enzyme specific to alpha-ketoglutarate has been reported in Thauera aromatica (Dorner and Boll, J. Bacteriol. 184 (14), 3975-83 (2002).

Protein
GenBank ID
GI Number
Organism

korA
BAB21494
12583691

Hydrogenobacter

thermophilus

korB
BAB21495
12583692

Hydrogenobacter

thermophilus

forD
BAB62132.1
14970994

Hydrogenobacter

thermophilus

forA
BAB62133.1
14970995

Hydrogenobacter

thermophilus

forB
BAB62134.1
14970996

Hydrogenobacter

thermophilus

forG
BAB62135.1
14970997

Hydrogenobacter

thermophilus

forE
BAB62136.1
14970998

Hydrogenobacter

thermophilus

Clim_0204
ACD89303.1
189339900

Chlorobium limicola

Clim_0205
ACD89302.1
189339899

Chlorobium limicola

Clim_1123
ACD90192.1
189340789

Chlorobium limicola

Clim_1124
ACD90193.1
189340790

Chlorobium limicola

korA
CAA12243.2
19571179

Thauera aromatica

korB
CAD27440.1
19571178

Thauera aromatica

L. Pyruvate Carboxylase.

Pyruvate carboxylase (EC 6.4.1.1) directly converts pyruvate to oxaloacetate at the cost of one ATP. Pyruvate carboxylase enzymes are encoded by PYC1 (Walker et al., Biochem. Biophys. Res. Commun. 176:1210-1217 (1991) and PYC2 (Walker et al., supra) in Saccharomyces cerevisiae, and pyc in Mycobacterium smegmatis (Mukhopadhyay and Purwantini, Biochim. Biophys. Acta 1475:191-206 (2000)).

Protein
GenBank ID
GI Number
Organism

PYC1
NP_011453
6321376

Saccharomyces cerevisiae

PYC2
NP_009777
6319695

Saccharomyces cerevisiae

Pyc
YP_890857.1
118470447

Mycobacterium smegmatis

M. Malic Enzyme.

Malic enzyme can be applied to convert CO₂and pyruvate to malate at the expense of one reducing equivalent. Malic enzymes for this purpose can include, without limitation, malic enzyme (NAD-dependent) and malic enzyme (NADP-dependent). For example, one of the E. coli malic enzymes (Takeo, J. Biochem. 66:379-387 (1969)) or a similar enzyme with higher activity can be expressed to enable the conversion of pyruvate and CO₂to malate. By fixing carbon to pyruvate as opposed to PEP, malic enzyme allows the high-energy phosphate bond from PEP to be conserved by pyruvate kinase whereby ATP is generated in the formation of pyruvate or by the phosphotransferase system for glucose transport. Although malic enzyme is typically assumed to operate in the direction of pyruvate formation from malate, overexpression of the NAD-dependent enzyme, encoded by maeA, has been demonstrated to increase succinate production in E. coli while restoring the lethal delta pfl-delta ldhA phenotype (inactive or deleted pfl and ldhA) under anaerobic conditions by operating in the carbon-fixing direction (Stols and Donnelly, Appl. Environ. Microbiol. 63(7) 2695-2701 (1997)). A similar observation was made upon overexpressing the malic enzyme from Ascaris suum in E. coli (Stols et al., Appl. Biochem. Biotechnol. 63-65(1), 153-158 (1997)). The second E. coli malic enzyme, encoded by maeB, is NADP-dependent and also decarboxylates oxaloacetate and other alpha-keto acids (Iwakura et al., J. Biochem. 85(5):1355-65 (1979)).

Protein
GenBank ID
GI Number
Organism

maeA
NP_415996
90111281

Escherichia coli

maeB
NP_416958
16130388

Escherichia coli

NAD-ME
P27443
126732

Ascaris suum

PEP synthetase: Also, known as pyruvate water dikinase, this enzyme converts pyruvate back into PEP at the expense of two ATP equivalents. It converts ATP into AMP. In E coli, this enzyme is encoded by ppsA. It is functional mainly during gluconeogenesis and provides the biomass precursors (Cooper and Kornberg, Biochim Biophys Acta, 104(2); 618-20, (1965)). Its activity is regulated by a regulatory protein encoded by ppsR that catalyzes both the P_i-dependent activation and ADP/ATP-dependent inactivation of PEP synthetase. PEP synthetase is protected from inactivation by the presence of pyruvate (Brunell, BMC Biochem. January 3; 11:1, (2010)). The overexpression of this enzyme has been shown to increase the production of aromatic amino acids by increasing availability of PEP, which is a precursor for aromatic amino acid biosynthesis pathways (Yi et al., Biotechnol Prog., 18(6):1141-8., (2002); Patnaik and Liao. Appl Environ Microbiol. 1994 November; 60(11):3903-8 (2001))). This enzyme has been studied in other organisms, such as Pyrococcus furiosus (Hutchins et al., J Bacteriol., 183(2):709-15 (2001)) and Psuedomonas fluorescens (J Biotechnol. 2013 Sep. 10; 167(3):309-15 (2013)).

Protein
GenBank ID
GI Number
Organism

ppsA
NP_416217.1
16129658

Escherichia coli

ppsA
CAA56785.1
967060

Pyrococcus furiosus

pps
EFQ61998.1
311283408

Pseudomonas fluorescens

Example X
1,3-Butanediol, Crotyl Alcohol, 3-Buten-2-ol, and Butadiene Synthesis Enzymes

This Example provides genes that can be used for conversion of acetyl-CoA to 1,3-butanediol, crotyl alcohol, 3-buten-2-ol, butadiene as depicted in the pathways of FIGS. 5 and 6.

FIG. 5. Pathways for converting 1,3-butanediol to 3-buten-2-ol and/or butadiene. A) acetyl-CoA carboxylase, B) an acetoacetyl-CoA synthase, C) an acetyl-CoA:acetyl-CoA acyltransferase, D) an acetoacetyl-CoA reductase (ketone reducing), E) a 3-hydroxybutyryl-CoA reductase (aldehyde forming), F) a 3-hydroxybutyryl-CoA hydrolase, transferase or synthetase, G) a 3-hydroxybutyrate reductase, H) a 3-hydroxybutyraldehyde reductase, I) chemical dehydration or corresponding step in FIG. 6, J) a 3-hydroxybutyryl-CoA dehydratase, K) a crotonyl-CoA reductase (aldehyde forming), L) a crotonyl-CoA hydrolase, transferase or synthetase, M) a crotonate reductase, N) a crotonaldehyde reductase, O) a crotyl alcohol kinase, P) a 2-butenyl-4-phosphate kinase, Q) a butadiene synthase, R) a crotyl alcohol diphosphokinase, S) chemical dehydration or a crotyl alcohol dehydratase, T) a butadiene synthase (monophosphate), T) a butadiene synthase (monophosphate), U) a crotonyl-CoA reductase (alcohol forming), and V) a 3-hydroxybutyryl-CoA reductase (alcohol forming).

A. Acetyl-CoA Carboxylase.

Acetyl-CoA carboxylase (EC 6.4.1.2) catalyzes the ATP-dependent carboxylation of acetyl-CoA to malonyl-CoA. This enzyme is biotin dependent and is the first reaction of fatty acid biosynthesis initiation in several organisms. Exemplary enzymes are encoded by accABCD of E. coli (Davis et al, J Biol Chem 275:28593-8 (2000)), ACC1 of Saccharomyces cerevisiae and homologs (Sumper et al, Methods Enzym 71:34-7 (1981)).

Protein
GenBank ID
GI Number
Organism

ACC1
CAA96294.1
1302498

Saccharomyces

KLLA0F06072g
XP_455355.1
50310667

Kluyveromyces lactis

ACC1
XP_718624.1
68474502

Candida albicans

YALI0C11407p
XP_501721.1
50548503

Yarrowia lipolytica

ANI_1_1724104
XP_001395476.1
145246454

Aspergillus niger

accA
AAC73296.1
1786382

Escherichia coli

accB
AAC76287.1
1789653

Escherichia coli

accC
AAC76288.1
1789654

Escherichia coli

accD
AAC75376.1
1788655

Escherichia coli

B. Acetoacetyl-CoA Synthase.

The conversion of malonyl-CoA and acetyl-CoA substrates to acetoacetyl-CoA can be catalyzed by a CoA synthetase in the 2.3.1 family of enzymes. Several enzymes catalyzing the CoA synthetase activities have been described in the literature and represent suitable candidates. 3-Oxoacyl-CoA products such as acetoacetyl-CoA, 3-oxopentanoyl-CoA, 3-oxo-5-hydroxypentanoyl-CoA can be synthesized from acyl-CoA and malonyl-CoA substrates by 3-oxoacyl-CoA synthases. As enzymes in this class catalyze an essentially irreversible reaction, they are particularly useful for metabolic engineering applications for overproducing metabolites, fuels or chemicals derived from 3-oxoacyl-CoA intermediates such as acetoacetyl-CoA. Acetoacetyl-CoA synthase, for example, has been heterologously expressed in organisms that biosynthesize butanol (Lan et al, PNAS USA (2012)) and poly-(3-hydroxybutyrate) (Matsumoto et al, Biosci Biotech Biochem, 75:364-366 (2011). An acetoacetyl-CoA synthase (EC 2.3.1.194) enzyme (FhsA) has been characterized in the soil bacterium Streptomyces sp. CL190 where it participates in mevalonate biosynthesis (Okamura et al, PNAS USA 107:11265-70 (2010)). Other acetoacetyl-CoA synthase genes can be identified by sequence homology to fhsA.

Protein
GenBank ID
GI
Organism

fhsA
BAJ83474.1
325302227

Streptomyces sp CL190

AB183750.1:
BAD86806.1
57753876

Streptomyces sp.

11991..12971

KO-3988

epzT
ADQ43379.1
312190954

Streptomyces

cinnamonensis

ppzT
CAX48662.1
238623523

Streptomyces anulatus

O3I_22085
ZP_09840373.1
378817444

Nocardia brasiliensis

C. Acetyl-CoA:Acetyl-CoA Acyltransferase (Acetoacetyl-CoA Thiolase).

Acetoacetyl-CoA thiolase (also known as acetyl-CoA acetyltransferase) converts two molecules of acetyl-CoA into one molecule each of acetoacetyl-CoA and CoA. Exemplary acetoacetyl-CoA thiolase enzymes include the gene products of atoB from E. coli (Martin et al., Nat. Biotechnol 21:796-802 (2003)), thlA and thlB from C. acetobutylicum (Hanai et al., Appl Environ Microbiol 73:7814-7818 (2007); Winzer et al., J. Mol. Microbiol Biotechnol 2:531-541 (2000), and ERG10 from S. cerevisiae Hiser et al., J. Biol. Chem. 269:31383-31389 (1994)). The acetoacetyl-CoA thiolase from Zoogloea ramigera is irreversible in the biosynthetic direction and a crystal structure is available (Merilainen et al, Biochem 48: 11011-25 (2009)). These genes/proteins are identified in the Table below.

Gene
GenBank ID
GI Number
Organism

AtoB
NP_416728
16130161

Escherichia coli

ThlA
NP_349476.1
15896127

Clostridium

ThlB
NP_149242.1
15004782

Clostridium

ERG10
NP_015297
6325229

Saccharomyces

phbA
P07097.4
135759

Zoogloea ramigera

D. Acetoacetyl-CoA Reductase.

A suitable enzyme activity is 1.1.1.a Oxidoreductase (oxo to alcohol). See herein. In addition, Acetoacetyl-CoA reductase (EC 1.1.1.36) catalyzes the reduction of acetoacetyl-CoA to 3-hydroxybutyryl-CoA. This enzyme participates in the acetyl-CoA fermentation pathway to butyrate in several species of Clostridia and has been studied in detail (Jones et al., Microbiol Rev. 50:484-524 (1986)). Acetoacetyl-CoA reductase also participates in polyhydroxybutyrate biosynthesis in many organisms, and has also been used in metabolic engineering applications for overproducing PHB and 3-hydroxyisobutyrate (Liu et al., Appl. Microbiol. Biotechnol. 76:811-818 (2007); Qui et al., Appl. Microbiol. Biotechnol. 69:537-542 (2006)). The enzyme from Clostridium acetobutylicum, encoded by hbd, has been cloned and functionally expressed in E. coli (Youngleson et al., J Bacteriol. 171:6800-6807 (1989)). Additional gene candidates include phbB from Zoogloea ramigera (Ploux et al., Eur. J Biochem. 174:177-182 (1988)) and phaB from Rhodobacter sphaeroides (Alber et al., Mol. Microbiol 61:297-309 (2006)). The Z. ramigera gene is NADPH-dependent and the gene has been expressed in E. coli (Peoples et al., Mol. Microbiol 3:349-357 (1989)). Substrate specificity studies on the gene led to the conclusion that it could accept 3-oxopropionyl-CoA as a substrate besides acetoacetyl-CoA (Ploux et al., Eur. J Biochem. 174:177-182 (1988)). Additional genes include phaB in Paracoccus denitrificans, Hbd1 (C-terminal domain) and Hbd2 (N-terminal domain) in Clostridium kluyveri (Hillmer and Gottschalk, Biochim. Biophys. Acta 3334:12-23 (1974)) and HSD17B10 in Bos taurus (Wakil et al., J Biol. Chem. 207:631-638 (1954)). The enzyme from Paracoccus denitrificans has been functionally expressed and characterized in E. coli (Yabutani et al., FEMS Microbiol Lett. 133:85-90 (1995)). A number of similar enzymes have been found in other species of Clostridia and in Metallosphaera sedula (Berg et al., Science. 318:1782-1786 (2007)). The enzyme from Candida tropicalis is a component of the peroxisomal fatty acid beta-oxidation multifunctional enzyme type 2 (MFE-2). The dehydrogenase B domain of this protein is catalytically active on acetoacetyl-CoA. The domain has been functionally expressed in E. coli, a crystal structure is available, and the catalytic mechanism is well-understood (Ylianttila et al., Biochem Biophys Res Commun 324:25-30 (2004); Ylianttila et al., J Mol Biol 358:1286-1295 (2006)).

Protein
Genbank ID
GI Number
Organism

fadB
P21177.2
119811

Escherichia coli

fadJ
P77399.1
3334437

Escherichia coli

paaH
NP_415913.1
16129356

Escherichia coli

Hbd2
EDK34807.1
146348271

Clostridium kluyveri

Hbd1
EDK32512.1
146345976

Clostridium kluyveri

phaC
NP_745425.1
26990000

Pseudomonas putida

paaC
ABF82235.1
106636095

Pseudomonas fluorescens

HSD17B10
O02691.3
3183024

Bos taurus

phbB
P23238.1
130017

Zoogloea ramigera

phaB
YP_353825.1
77464321

Rhodobacter sphaeroides

phaB
BAA08358
675524

Paracoccus denitrificans

Hbd
NP_349314.1
15895965

Clostridium acetobutylicum

Hbd
AAM14586.1
20162442

Clostridium beijerinckii

Msed_1423
YP_001191505
146304189

Metallosphaera sedula

Msed_0399
YP_001190500
146303184

Metallosphaera sedula

Msed_0389
YP_001190490
146303174

Metallosphaera sedula

Msed_1993
YP_001192057
146304741

Metallosphaera sedula

Fox2
Q02207
399508

Candida tropicalis

E) 3-Hydroxybutyryl-CoA Reductase (Aldehyde Forming).

An EC 1.2.1.b Oxidoreductase (acyl-CoA to aldehyde) provides suitable enzyme activity. Acyl-CoA reductases or acylating aldehyde dehydrogenases reduce an acyl-CoA to its corresponding aldehyde. Exemplary enzymes include fatty acyl-CoA reductase, succinyl-CoA reductase (EC 1.2.1.76), acetyl-CoA reductase, butyryl-CoA reductase, propionyl-CoA reductase (EC 1.2.1.3) and others shown in the table below.

EC Number
Enzyme name

1.2.1.10
Acetaldehyde dehydrogenase (acetylating)

1.2.1.42
(Fatty) acyl-CoA reductase

1.2.1.44
Cinnamoyl-CoA reductase

1.2.1.50
Long chain fatty acyl-CoA reductase

1.2.1.57
Butanal dehydrogenase

1.2.1.75
Malonate semialdehyde dehydrogenase

1.2.1.76
Succinate semialdehyde dehydrogenase

1.2.1.81
Sulfoacetaldehyde dehydrogenase

1.2.1.-
Propanal dehydrogenase

1.2.1.-
Hexanal dehydrogenase

1.2.1.-
4-Hydroxybutyraldehyde dehydrogenase

Exemplary fatty acyl-CoA reductases enzymes are encoded by acr1 of Acinetobacter calcoaceticus (Reiser, Journal of Bacteriology 179:2969-2975 (1997)) and Acinetobacter sp. M-1 (Ishige et al., Appl. Environ. Microbiol. 68:1192-1195 (2002)). Enzymes with succinyl-CoA reductase activity are encoded by sucD of Clostridium kluyveri (Sohling, J. Bacteriol. 178:871-880 (1996)) and sucD of P. gingivalis (Takahashi, J. Bacteriol 182:4704-4710 (2000)). Additional succinyl-CoA reductase enzymes participate in the 3-hydroxypropionate/4-hydroxybutyrate cycle of thermophilic archaea including Metallosphaera sedula (Berg et al., Science 318:1782-1786 (2007)) and Thermoproteus neutrophilus (Ramos-Vera et al., J Bacteriol., 191:4286-4297 (2009)). The M. sedula enzyme, encoded by Msed_0709, is strictly NADPH-dependent and also has malonyl-CoA reductase activity. The T. neutrophilus enzyme is active with both NADPH and NADH. The enzyme acylating acetaldehyde dehydrogenase in Pseudomonas sp, encoded by bphG, is yet another as it has been demonstrated to oxidize and acylate acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde and formaldehyde (Powlowski, J. Bacteriol. 175:377-385 (1993)). In addition to reducing acetyl-CoA to ethanol, the enzyme encoded by adhE in Leuconostoc mesenteroides has been shown to oxidize the branched chain compound isobutyraldehyde to isobutyryl-CoA (Kazahaya, J. Gen. Appl. Microbiol. 18:43-55 (1972); and Koo et al., Biotechnol Lett. 27:505-510 (2005)). Butyraldehyde dehydrogenase catalyzes a similar reaction, conversion of butyryl-CoA to butyraldehyde, in solventogenic organisms such as Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci Biotechnol Biochem., 71:58-68 (2007)). Exemplary propionyl-CoA reductase enzymes include pduP of Salmonella typhimurium LT2 (Leal, Arch. Microbiol. 180:353-361 (2003)) and eutE from E. coli (Skraly, WO Patent No. 2004/024876). The propionyl-CoA reductase of Salmonella typhimurium LT2, which naturally converts propionyl-CoA to propionaldehyde, also catalyzes the reduction of 5-hydroxyvaleryl-CoA to 5-hydroxypentanal (WO 2010/068953A2).

Protein
GenBank ID
GI Number
Organism

acr1
YP_047869.1
50086359

Acinetobacter calcoaceticus

acr1
AAC45217
1684886

Acinetobacter baylyi

acr1
BAB85476.1
18857901

Acinetobacter sp. Strain M-1

MSED_0709
YP_001190808.1
146303492

Metallosphaera sedula

Tneu_0421
ACB39369.1
170934108

Thermoproteus neutrophilus

sucD
P38947.1
172046062

Clostridium kluyveri

sucD
NP_904963.1
34540484

Porphyromonas gingivalis

bphG
BAA03892.1
425213

Pseudomonas sp

adhE
AAV66076.1
55818563

Leuconostoc mesenteroides

bld
AAP42563.1
31075383

Clostridium

saccharoperbutylacetonicum

pduP
NP_460996
16765381

Salmonella typhimurium LT2

eutE
NP_416950
16130380

Escherichia coli

An additional enzyme that converts an acyl-CoA to its corresponding aldehyde is malonyl-CoA reductase which transforms malonyl-CoA to malonic semialdehyde. Malonyl-CoA reductase is a key enzyme in autotrophic carbon fixation via the 3-hydroxypropionate cycle in thermoacidophilic archaeal bacteria (Berg, Science 318:1782-1786 (2007); and Thauer, Science 318:1732-1733 (2007)). The enzyme utilizes NADPH as a cofactor and has been characterized in Metallosphaera and Sulfolobus sp. (Alber et al., J. Bacteriol. 188:8551-8559 (2006); and Hugler, J. Bacteriol. 184:2404-2410 (2002)). The enzyme is encoded by Msed_0709 in Metallosphaera sedula (Alber et al., J. Bacteriol. 188:8551-8559 (2006); and Berg, Science 318:1782-1786 (2007)). A gene encoding a malonyl-CoA reductase from Sulfolobus tokodaii was cloned and heterologously expressed in E. coli (Alber et al., J. Bacteriol 188:8551-8559 (2006). This enzyme has also been shown to catalyze the conversion of methylmalonyl-CoA to its corresponding aldehyde (WO2007141208 (2007)). Although the aldehyde dehydrogenase functionality of these enzymes is similar to the bifunctional dehydrogenase from Chloroflexus aurantiacus, there is little sequence similarity. Both malonyl-CoA reductase enzyme candidates have high sequence similarity to aspartate-semialdehyde dehydrogenase, an enzyme catalyzing the reduction and concurrent dephosphorylation of aspartyl-4-phosphate to aspartate semialdehyde. Additional gene candidates can be found by sequence homology to proteins in other organisms including Sulfolobus solfataricus and Sulfolobus acidocaldarius and have been listed below. Yet another candidate for CoA-acylating aldehyde dehydrogenase is the ald gene from Clostridium beijerinckii (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999). This enzyme has been reported to reduce acetyl-CoA and butyryl-CoA to their corresponding aldehydes. This gene is very similar to eutE that encodes acetaldehyde dehydrogenase of Salmonella typhimurium and E. coli (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999).

Protein
GenBank ID
GI Number
Organism

Msed_0709
YP_001190808.1
146303492

Metallosphaera sedula

Mcr
NP_378167.1
15922498

Sulfolobus tokodaii

asd-2
NP_343563.1
15898958

Sulfolobus solfataricus

Saci_2370
YP_256941.1
70608071

Sulfolobus acidocaldarius

Ald
AAT66436
49473535

Clostridium beijerinckii

eutE
AAA80209
687645

Salmonella typhimurium

4-Hydroxybutyryl-CoA reductase catalyzes the reduction of 4-hydroxybutyryl-CoA to its corresponding aldehyde. Several acyl-CoA dehydrogenases are capable of catalyzing this activity. The succinate semialdehyde dehydrogenases (SucD) of Clostridium kluyveri and P. gingivalis were shown in ref (WO/2008/115840) to convert 4-hydroxybutyryl-CoA to 4-hydroxybutanal as part of a pathway to produce 1,4-butanediol. Many butyraldehyde dehydrogenases are also active on 4-hydroxybutyraldehyde, including bld of Clostridium saccharoperbutylacetonicum and bphG of Pseudomonas sp (Powlowski et al., J. Bacteriol. 175:377-385 (1993)). Yet another candidate is the ald gene from Clostridium beijerinckii (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999). This gene is very similar to eutE that encodes acetaldehyde dehydrogenase of Salmonella typhimurium and E. coli (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999). These and additional proteins with 4-hydroxybutyryl-CoA reductase activity are identified below.

Protein
GenBank ID
GI Number
Organism

bphG
BAA03892.1
425213

Pseudomonas sp

ald
YP_001310903.1
150018649

Clostridium beijerinckii NCIMB 8052

Ald
ZP_03778292.1
225569267

Clostridium hylemonae DSM 15053

Ald
ZP_03705305.1
225016072

Clostridium methylpentosum DSM 5476

Ald
ZP_03715465.1
225026273

Eubacterium hallii DSM 3353

Ald
ZP_01962381.1
153809713

Ruminococcus obeum ATCC 29174

Ald
YP_003701164.1
297585384

Bacillus selenitireducens MLS10

Ald
AAP42563.1
31075383

Clostridium

saccharoperbutylacetonicum N1-4

Ald
YP_795711.1
116334184

Lactobacillus brevis ATCC 367

Ald
YP_002434126.1
218782808

Desulfatibacillum alkenivorans AK-01

Ald
YP_001558295.1
160879327

Clostridium phytofermentans ISDg

Ald
ZP_02089671.1
160942363

Clostridium bolteae ATCC BAA-613

Ald
ZP_01222600.1
90414628

Photobacterium profundum 3TCK

Ald
YP_001452373.1
157145054

Citrobacter koseri ATCC BAA-895

Ald
NP_460996.1
16765381

Salmonella enterica
typhimurium

Ald
YP_003307836.1
269119659

Sebaldella termitidis ATCC 33386

Ald
ZP_04969437.1
254302079

Fusobacterium nucleatum subsp.

polymorphum ATCC 10953

Ald
YP_002892893.1
237808453

Tolumonas auensis DSM 9187

Ald
YP_426002.1
83592250

Rhodospirillum rubrum ATCC 11170

F) 3-Hydroxybutyryl-CoA Hydrolase, Transferase or Synthetase.

An EC 3.1.2.a CoA hydrolase, EC 2.8.3.a CoA transferase, and/or an EC 6.2.1.a CoA synthetase provide suitable enzyme activity. See below and herein.

G) 3-Hydroxybutyrate Reductase.

An EC 1.2.1.e Oxidoreductase (acid to aldehyde) provides suitable activity. See below and herein.

H) 3-Hydroxybutyraldehyde Reductase.

An EC 1.1.1.a Oxidoreductase (oxo to alcohol) provides suitable activity. See herein.

I) Chemical Dehydration or Alternatively See Corresponding Enzymatic Pathway in FIG. 6.
J) 3-Hydroxybutyryl-CoA Dehydratase.

An EC 4.2.1. Hydro-lyase provides suitable enzyme activity, and are described below and herein. The enoyl-CoA hydratase of Pseudomonas putida, encoded by ech, catalyzes the conversion of 3-hydroxybutyryl-CoA to crotonyl-CoA (Roberts et al., Arch. Microbiol 117:99-108 (1978)). This transformation is also catalyzed by the crt gene product of Clostridium acetobutylicum, the crt1 gene product of C. kluyveri, and other clostridial organisms Atsumi et al., Metab Eng 10:305-311 (2008); Boynton et al., J Bacteriol. 178:3015-3024 (1996); Hillmer et al., FEBS Lett. 21:351-354 (1972)). Additional enoyl-CoA hydratase candidates are phaA and phaB, of P. putida, and paaA and paaB from P. fluorescens (Olivera et al., Proc. Natl. Acad. Sci U.S.A. 95:6419-6424 (1998)). The gene product of pimF in Rhodopseudomonas palustris is predicted to encode an enoyl-CoA hydratase that participates in pimeloyl-CoA degradation (Harrison et al., Microbiology 151:727-736 (2005)). Lastly, a number of Escherichia coli genes have been shown to demonstrate enoyl-CoA hydratase functionality including maoC (Park et al., J Bacteriol. 185:5391-5397 (2003)), paaF (Ismail et al., Eur. J Biochem. 270:3047-3054 (2003); Park et al., Appl. Biochem. Biotechnol 113-116:335-346 (2004); Park et al., Biotechnol Bioeng 86:681-686 (2004)) and paaG (Ismail et al., Eur. J Biochem. 270:3047-3054 (2003); Park and Lee, Appl. Biochem. Biotechnol 113-116:335-346 (2004); Park and Yup, Biotechnol Bioeng 86:681-686 (2004)).

Protein
GenBank No.
GI No.
Organism

ech
NP_745498.1
26990073

Pseudomonas putida

crt
NP_349318.1
15895969

Clostridium acetobutylicum

crt1
YP_001393856
153953091

Clostridium kluyveri

phaA
ABF82233.1
26990002

Pseudomonas putida

phaB
ABF82234.1
26990001

Pseudomonas putida

paaA
NP_745427.1
106636093

Pseudomonas fluorescens

paaB
NP_745426.1
106636094

Pseudomonas fluorescens

maoC
NP_415905.1
16129348

Escherichia coli

paaF
NP_415911.1
16129354

Escherichia coli

paaG
NP_415912.1
16129355

Escherichia coli

K) Crotonyl-CoA Reductase (Aldehyde Forming).

An EC 1.2.1.b Oxidoreductase (acyl-CoA to aldehyde) provides suitable enzyme activity. Acyl-CoA reductases in the 1.2.1 family reduce an acyl-CoA to its corresponding aldehyde. Several acyl-CoA reductase enzymes have been described in the open literature and represent suitable candidates for this step. These are described above and herein.

L) Crotonyl-CoA Hydrolase, Transferase or Synthetase.

An EC 3.1.2.a CoA hydrolase, EC 2.8.3.a CoA transferase, and/or an EC 6.2.1.a CoA synthetase provide suitable enzyme activity, and are described herein and in the following sections.

EC 3.1.2.a CoA Hydrolase.

Enzymes in the 3.1.2 family hydrolyze acyl-CoA molecules to their corresponding acids. Several such enzymes have been described in the literature and represent suitable candidates for these steps.

For example, the enzyme encoded by acot12 from Rattus norvegicus brain (Robinson et al., Biochem. Biophys. Res. Commun. 71:959-965 (1976)) can react with butyryl-CoA, hexanoyl-CoA and malonyl-CoA. The human dicarboxylic acid thioesterase, encoded by acot8, exhibits activity on glutaryl-CoA, adipyl-CoA, suberyl-CoA, sebacyl-CoA, and dodecanedioyl-CoA (Westin et al., J. Biol. Chem. 280:38125-38132 (2005)). The closest E. coli homolog to this enzyme, tesB, can also hydrolyze a range of CoA thiolesters (Naggert et al., J Biol Chem 266:11044-11050 (1991)). A similar enzyme has also been characterized in the rat liver (Deana R., Biochem Int 26:767-773 (1992)). Additional enzymes with hydrolase activity in E. coli include ybgC, paaI, and ybdB (Kuznetsova, et al., FEMS Microbiol Rev, 2005, 29(2):263-279; Song et al., J Biol Chem, 2006, 281(16):11028-38). Though its sequence has not been reported, the enzyme from the mitochondrion of the pea leaf has a broad substrate specificity, with demonstrated activity on acetyl-CoA, propionyl-CoA, butyryl-CoA, palmitoyl-CoA, oleoyl-CoA, succinyl-CoA, and crotonyl-CoA (Zeiher et al., Plant. Physiol. 94:20-27 (1990)) The acetyl-CoA hydrolase, ACH1, from S. cerevisiae represents another candidate hydrolase (Buu et al., J. Biol. Chem. 278:17203-17209 (2003)).

Protein
GenBank Accession
GI Number
Organism

acot12
NP_570103.1
18543355

Rattus norvegicus

tesB
NP_414986
16128437

Escherichia coli

acot8
CAA15502
3191970

Homo sapiens

acot8
NP_570112
51036669

Rattus norvegicus

tesA
NP_415027
16128478

Escherichia coli

ybgC
NP_415264
16128711

Escherichia coli

paaI
NP_415914
16129357

Escherichia coli

ybdB
NP_415129
16128580

Escherichia coli

ACH1
NP_009538
6319456

Saccharomyces cerevisiae

Additional hydrolase enzymes include 3-hydroxyisobutyryl-CoA hydrolase which has been described to efficiently catalyze the conversion of 3-hydroxyisobutyryl-CoA to 3-hydroxyisobutyrate during valine degradation (Shimomura et al., J Biol Chem. 269:14248-14253 (1994)). Genes encoding this enzyme include hibch of Rattus norvegicus (Shimomura et al., Methods Enzymol. 324:229-240 (2000)) and Homo sapiens (Shimomura et al., supra). Similar gene candidates can also be identified by sequence homology, including hibch of Saccharomyces cerevisiae and BC_2292 of Bacillus cereus.

Protein
GenBank No.
GI Number
Organism

hibch
Q5XIE6.2
146324906

Rattus norvegicus

hibch
Q6NVY1.2
146324905

Homo sapiens

hibch
P28817.2
2506374

Saccharomyces cerevisiae

BC_2292
AP09256
29895975

Bacillus cereus

EC 2.8.3.a CoA Transferase.

Enzymes in the 2.8.3 family catalyze the reversible transfer of a CoA moiety from one molecule to another. Several CoA transferase enzymes have been described in the open literature and represent suitable candidates for these steps. These are described below.

Many transferases have broad specificity and thus can utilize CoA acceptors as diverse as acetate, succinate, propionate, butyrate, 2-methylacetoacetate, 3-ketohexanoate, 3-ketopentanoate, valerate, crotonate, 3-mercaptopropionate, propionate, vinylacetate, butyrate, among others. For example, an enzyme from Roseburia sp. A2-183 was shown to have butyryl-CoA:acetate:CoA transferase and propionyl-CoA:acetate:CoA transferase activity (Charrier et al., Microbiology 152, 179-185 (2006)). Close homologs can be found in, for example, Roseburia intestinalis L1-82, Roseburia inulinivorans DSM 16841, Eubacterium rectale ATCC 33656. Another enzyme with propionyl-CoA transferase activity can be found in Clostridium propionicum (Selmer et al., Eur J Biochem 269, 372-380 (2002)). This enzyme can use acetate, (R)-lactate, (S)-lactate, acrylate, and butyrate as the CoA acceptor (Selmer et al., Eur J Biochem 269, 372-380 (2002); Schweiger and Buckel, FEBS Letters, 171(1) 79-84 (1984)). Close homologs can be found in, for example, Clostridium novyi NT, Clostridium beijerinckii NCIMB 8052, and Clostridium botulinum C str. Eklund. YgfH encodes a propionyl CoA:succinate CoA transferase in E. coli (Haller et al., Biochemistry, 39(16) 4622-4629). Close homologs can be found in, for example, Citrobacter youngae ATCC 29220, Salmonella enterica subsp. arizonae serovar, and Yersinia intermedia ATCC 29909.

GI

Protein
GenBank ID
Number
Organism

Ach1
AAX19660.1
60396828

Roseburia sp. A2-183

ROSINTL182_07121
ZP_04743841.2
257413684

Roseburia intestinalis L1-82

ROSEINA2194_03642
ZP_03755203.1
225377982

Roseburia inulinivorans

EUBREC_3075
YP_002938937.1
238925420

Eubacterium rectale ATCC 33656

Pct
CAB77207.1
7242549

Clostridium propionicum

NT01CX_2372
YP_878445.1
118444712

Clostridium novyi NT

Cbei_4543
YP_001311608.1
150019354

Clostridium beijerinckii

CBC_A0889
ZP_02621218.1
168186583

Clostridium botulinum C str. Eklund

ygfH
NP_417395.1
16130821

Escherichia coli

CIT292_04485
ZP_03838384.1
227334728

Citrobacter youngae ATCC 29220

SARI_04582
YP_001573497.1
161506385

Salmonella enterica subsp. arizonae

serovar

yinte0001_14430
ZP_04635364.1
238791727

Yersinia intermedia ATCC 29909

An additional candidate enzyme is the two-unit enzyme encoded by pcaI and pcaJ in Pseudomonas, which has been shown to have 3-oxoadipyl-CoA/succinate transferase activity (Kaschabek et al., supra). Similar enzymes based on homology exist in Acinetobacter sp. ADP1 (Kowalchuk et al., Gene 146:23-30 (1994)) and Streptomyces coelicolor. Additional exemplary succinyl-CoA:3:oxoacid-CoA transferases are present in Helicobacter pylori (Corthesy-Theulaz et al., J. Biol. Chem. 272:25659-25667 (1997)) and Bacillus subtilis (Stols et al., Protein. Expr. Purif. 53:396-403 (2007)). These proteins are identified below.

Protein
GenBank ID
GI Number
Organism

pcaI
AAN69545.1
24985644

Pseudomonas putida

pcaJ
NP_746082.1
26990657

Pseudomonas putida

pcaI
YP_046368.1
50084858

Acinetobacter sp. ADP1

pcaJ
AAC37147.1
141776

Acinetobacter sp. ADP1

pcaI
NP_630776.1
21224997

Streptomyces coelicolor

pcaJ
NP_630775.1
21224996

Streptomyces coelicolor

HPAG1_0676
YP_627417
108563101

Helicobacter pylori

HPAG1_0677
YP_627418
108563102

Helicobacter pylori

ScoA
NP_391778
16080950

Bacillus subtilis

ScoB
NP_391777
16080949

Bacillus subtilis

A CoA transferase that can utilize acetate as the CoA acceptor is acetoacetyl-CoA transferase, encoded by the E. coli atoA (alpha subunit) and atoD (beta subunit) genes (Vanderwinkel et al., Biochem. Biophys. Res Commun. 33:902-908 (1968); Korolev et al., Acta Crystallogr. D Biol Crystallogr. 58:2116-2121 (2002)). This enzyme has also been shown to transfer the CoA moiety to acetate from a variety of branched and linear acyl-CoA substrates, including isobutyrate (Matthies et al., Appl Environ Microbiol 58:1435-1439 (1992)), valerate (Vanderwinkel et al., supra) and butanoate (Vanderwinkel et al., supra). Similar enzymes exist in Corynebacterium glutamicum ATCC 13032 (Duncan et al., Appl Environ Microbiol 68:5186-5190 (2002)), Clostridium acetobutylicum (Cary et al., Appl Environ Microbiol 56:1576-1583 (1990)), and Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci. Biotechnol Biochem. 71:58-68 (2007)). These proteins are identified below.

Protein
GenBank ID
GI
Organism

atoA
P76459.1
2492994

Escherichia coli K12

atoD
P76458.1
2492990

Escherichia coli K12

actA
YP_226809.1
62391407

Corynebacterium glutamicum ATCC

cg0592
YP_224801.1
62389399

Corynebacterium glutamicum ATCC

ctfA
NP_149326.1
15004866

Clostridium acetobutylicum

ctfB
NP_149327.1
15004867

Clostridium acetobutylicum

ctfA
AAP42564.1
31075384

Clostridium

ctfB
AAP42565.1
31075385

Clostridium

Additional exemplary transferase candidates are catalyzed by the gene products of cat1, cat2, and cat3 of Clostridium kluyveri which have been shown to exhibit succinyl-CoA, 4-hydroxybutyryl-CoA, and butyryl-CoA transferase activity, respectively (Seedorf et al., supra; Sohling et al., Eur. J Biochem. 212:121-127 (1993); Sohling et al., J Bacteriol. 178:871-880 (1996)). Similar CoA transferase activities are also present in Trichomonas vaginalis (van Grinsven et al., J. Biol. Chem. 283:1411-1418 (2008)) and Trypanosoma brucei (Riviere et al., J. Biol. Chem. 279:45337-45346 (2004)). These proteins are identified below.

The glutaconate-CoA-transferase (EC 2.8.3.12) enzyme from anaerobic bacterium Acidaminococcus fermentans reacts with diacid glutaconyl-CoA and 3-butenoyl-CoA (Mack et al., FEBS Lett. 405:209-212 (1997)). The genes encoding this enzyme are gctA and gctB. This enzyme has reduced but detectable activity with other CoA derivatives including glutaryl-CoA, 2-hydroxyglutaryl-CoA, adipyl-CoA and acrylyl-CoA (Buckel et al., Eur. J. Biochem. 118:315-321 (1981)). The enzyme has been cloned and expressed in E. coli (Mack et al., Eur. J. Biochem. 226:41-51 (1994)). These proteins are identified below.

Protein
GenBank ID
GI Number
Organism

gctA
CAA57199.1
559392

Acidaminococcus fermentans

gctB
CAA57200.1
559393

Acidaminococcus fermentans

EC 6.2.1.a CoA Synthase (Acid-Thiol Ligase).

The conversion of acyl-CoA substrates to their acid products can be catalyzed by a CoA acid-thiol ligase or CoA synthetase in the 6.2.1 family of enzymes, several of which are reversible. Several enzymes catalyzing CoA acid-thiol ligase or CoA synthetase activities have been described in the literature and represent suitable candidates for these steps. For example, ADP-forming acetyl-CoA synthetase (ACD, EC 6.2.1.13) is an enzyme that couples the conversion of acyl-CoA esters to their corresponding acids with the concomitant synthesis of ATP. ACD I from Archaeoglobus fulgidus, encoded by AF1211, was shown to operate on a variety of linear and branched-chain substrates including isobutyrate, isopentanoate, and fumarate (Musfeldt et al., J Bacteriol. 184:636-644 (2002)). A second reversible ACD in Archaeoglobus fulgidus, encoded by AF1983, was also shown to have a broad substrate range with high activity on cyclic compounds phenylacetate and indoleacetate (Musfeldt and Schonheit, J Bacteriol. 184:636-644 (2002)). The enzyme from Haloarcula marismortui (annotated as a succinyl-CoA synthetase) accepts propionate, butyrate, and branched-chain acids (isovalerate and isobutyrate) as substrates, and was shown to operate in the forward and reverse directions (Brasen et al., Arch Microbiol 182:277-287 (2004)). The ACD encoded by PAE3250 from hyperthermophilic crenarchaeon Pyrobaculum aerophilum showed the broadest substrate range of all characterized ACDs, reacting with acetyl-CoA, isobutyryl-CoA (preferred substrate) and phenylacetyl-CoA (Brasen et al, supra). Directed evolution or engineering can be used to modify this enzyme to operate at the physiological temperature of the host organism. The enzymes from A. fulgidus, H. marismortui and P. aerophilum have all been cloned, functionally expressed, and characterized in E. coli (Brasen and Schonheit, supra; Musfeldt and Schonheit, J Bacteriol. 184:636-644 (2002)). An additional candidate is succinyl-CoA synthetase, encoded by sucCD of E. coli and LSC1 and LSC2 genes of Saccharomyces cerevisiae. These enzymes catalyze the formation of succinyl-CoA from succinate with the concomitant consumption of one ATP in a reaction which is reversible in vivo (Buck et al., Biochemistry 24:6245-6252 (1985)). The acyl CoA ligase from Pseudomonas putida has been demonstrated to work on several aliphatic substrates including acetic, propionic, butyric, valeric, hexanoic, heptanoic, and octanoic acids and on aromatic compounds such as phenylacetic and phenoxyacetic acids (Fernandez-Valverde et al., Appl. Environ. Microbiol. 59:1149-1154 (1993)). A related enzyme, malonyl CoA synthetase (6.3.4.9) from Rhizobium leguminosarum could convert several diacids, namely, ethyl-, propyl-, allyl-, isopropyl-, dimethyl-, cyclopropyl-, cyclopropylmethylene-, cyclobutyl-, and benzyl-malonate into their corresponding monothioesters (Pohl et al., J. Am. Chem. Soc. 123:5822-5823 (2001)).

Protein
GenBank ID
GI Number
Organism

AF1211
NP_070039.1
11498810

Archaeoglobus fulgidus

AF1983
NP_070807.1
11499565

Archaeoglobus fulgidus

Scs
YP_135572.1
55377722

Haloarcula marismortui

PAE3250
NP_560604.1
18313937

Pyrobaculum aerophilum

sucC
NP_415256.1
16128703

Escherichia coli

sucD
AAC73823.1
1786949

Escherichia coli

LSC1
NP_014785
6324716

Saccharomyces cerevisiae

LSC2
NP_011760
6321683

Saccharomyces cerevisiae

paaF
AAC24333.2
22711873

Pseudomonas putida

matB
AAC83455.1
3982573

Rhizobium leguminosarum

Another candidate enzyme for these steps is 6-carboxyhexanoate-CoA ligase, also known as pimeloyl-CoA ligase (EC 6.2.1.14), which naturally activates pimelate to pimeloyl-CoA during biotin biosynthesis in gram-positive bacteria. The enzyme from Pseudomonas mendocina, cloned into E. coli, was shown to accept the alternate substrates hexanedioate and nonanedioate (Binieda et al., Biochem. J 340 (Pt 3):793-801 (1999)). Other candidates are found in Bacillus subtilis (Bower et al., J Bacteriol. 178:4122-4130 (1996)) and Lysinibacillus sphaericus (formerly Bacillus sphaericus) (Ploux et al., Biochem. J 287 (Pt 3):685-690 (1992)).

Protein
GenBank ID
GI Number
Organism

bioW
NP_390902.2
50812281

Bacillus subtilis

bioW
CAA10043.1
3850837

Pseudomonas mendocina

bioW
P22822.1
115012

Bacillus sphaericus

Additional CoA-ligases include the rat dicarboxylate-CoA ligase for which the sequence is yet uncharacterized (Vamecq et al., Biochem. J 230:683-693 (1985)), either of the two characterized phenylacetate-CoA ligases from P. chrysogenum (Lamas-Maceiras et al., Biochem. J 395:147-155 (2006); Wang et al., 360:453-458 (2007)), the phenylacetate-CoA ligase from Pseudomonas putida (Martinez-Blanco et al., J Biol Chem 265:7084-7090 (1990)) and the 6-carboxyhexanoate-CoA ligase from Bacillus subtilis (Bower et al. J Bacteriol 178(14):4122-4130 (1996)). Acetoacetyl-CoA synthetases from Mus musculus (Hasegawa et al., Biochim Biophys Acta 1779:414-419 (2008)) and Homo sapiens (Ohgami et al., Biochem. Pharmacol. 65:989-994 (2003)) naturally catalyze the ATP-dependent conversion of acetoacetate into acetoacetyl-CoA.

Protein
Accession No.
GI No.
Organism

phl
CAJ15517.1
77019264

Penicillium chrysogenum

phlB
ABS19624.1
152002983

Penicillium chrysogenum

paaF
AAC24333.2
22711873

Pseudomonas putida

bioW
NP_390902.2
50812281

Bacillus subtilis

AACS
NP_084486.1
21313520

Mus musculus

AACS
NP_076417.2
31982927

Homo sapiens

Like enzymes in other classes, certain enzymes in the EC class 6.2.1 have been determined to have broad substrate specificity. The acyl CoA ligase from Pseudomonas putida has been demonstrated to work on several aliphatic substrates including acetic, propionic, butyric, valeric, hexanoic, heptanoic, and octanoic acids and on aromatic compounds such as phenylacetic and phenoxyacetic acids (Fernandez-Valverde et al., Applied and Environmental Microbiology 59:1149-1154 (1993)). A related enzyme, malonyl CoA synthetase (6.3.4.9) from Rhizobium trifolii could convert several diacids, namely, ethyl-, propyl-, allyl-, isopropyl-, dimethyl-, cyclopropyl-, cyclopropylmethylene-, cyclobutyl-, and benzyl-malonate into their corresponding monothioesters (Pohl et al., J. Am. Chem. Soc. 123:5822-5823 (2001)).

M) Crotonate Reductase.

A suitable enzyme activity is an 1.2.1.e Oxidoreductase (acid to aldehyde), which include the following.

The conversion of an acid to an aldehyde is thermodynamically unfavorable and typically requires energy-rich cofactors and multiple enzymatic steps. Direct conversion of the acid to aldehyde by a single enzyme is catalyzed by an acid reductase enzyme in the 1.2.1 family. Exemplary acid reductase enzymes include carboxylic acid reductase, alpha-aminoadipate reductase and retinoic acid reductase. Carboxylic acid reductase (CAR), found in Nocardia iowensis, catalyzes the magnesium, ATP and NADPH-dependent reduction of carboxylic acids to their corresponding aldehydes (Venkitasubramanian et al., J Biol. Chem. 282:478-485 (2007)). The natural substrate of this enzyme is benzoate and the enzyme exhibits broad acceptance of aromatic substrates including p-toluate (Venkitasubramanian et al., Biocatalysis in Pharmaceutical and Biotechnology Industries. CRC press (2006)). The enzyme from Nocardia iowensis, encoded by car, was cloned and functionally expressed in E. coli (Venkitasubramanian et al., J Biol. Chem. 282:478-485 (2007)). CAR requires post-translational activation by a phosphopantetheine transferase (PPTase) that converts the inactive apo-enzyme to the active holo-enzyme (Hansen et al., Appl. Environ. Microbiol 75:2765-2774 (2009)). Expression of the npt gene, encoding a specific PPTase, product improved activity of the enzyme. An additional enzyme candidate found in Streptomyces griseus is encoded by the griC and griD genes. This enzyme is believed to convert 3-amino-4-hydroxybenzoic acid to 3-amino-4-hydroxybenzaldehyde as deletion of either griC or griD led to accumulation of extracellular 3-acetylamino-4-hydroxybenzoic acid, a shunt product of 3-amino-4-hydroxybenzoic acid metabolism (Suzuki, et al., J. Antibiot. 60(6):380-387 (2007)). Co-expression of griC and griD with SGR_665, an enzyme similar in sequence to the Nocardia iowensis npt, can be beneficial.

Gene
GenBank Accession
GI No.
Organism

car
AAR91681.1
40796035

Nocardia iowensis

npt
ABI83656.1
114848891

Nocardia iowensis

griC
YP_001825755.1
182438036

Streptomyces griseus

griD
YP_001825756.1
182438037

Streptomyces griseus

Additional car and npt genes can be identified based on sequence homology.

GenBank

Gene name
GI No.
Accession No.
Organism

fadD9
121638475
YP_978699.1

Mycobacterium

bovis BCG

BCG_2812c
121638674
YP_978898.1

Mycobacterium

bovis BCG

nfa20150
54023983
YP_118225.1

Nocardia farcinica

IFM 10152

nfa40540
54026024
YP_120266.1

Nocardia farcinica

IFM 10152

SGR_6790
182440583
YP_001828302.1

Streptomyces

griseus subsp.

griseus NBRC

13350

SGR_665
182434458
YP_001822177.1

Streptomyces

griseus subsp.

griseus NBRC

13350

MSMEG_2956
YP_887275.1
YP_887275.1

Mycobacterium

smegmatis MC2

155

MSMEG_5739
YP_889972.1
118469671

Mycobacterium

smegmatis MC2

155

MSMEG_2648
YP_886985.1
118471293

Mycobacterium

smegmatis MC2

155

MAP1040c
NP_959974.1
41407138

Mycobacterium

avium subsp.

paratuberculosis

K-10

MAP2899c
NP_961833.1
41408997

Mycobacterium

avium subsp.

paratuberculosis

K-10

MMAR_2117
YP_001850422.1
183982131

Mycobacterium

marinum M

MMAR_2936
YP_001851230.1
183982939

Mycobacterium

marinum M

MMAR_1916
YP_001850220.1
183981929

Mycobacterium

marinum M

TpauDRAFT_
ZP_04027864.1
227980601

Tsukamurella

33060

paurometabola

DSM 20162

TpauDRAFT_
ZP_04026660.1
ZP_04026660.1

Tsukamurella

20920

paurometabola

DSM 20162

CPCC7001_1320
ZP 05045132.1
254431429

Cyanobium

PCC7001

DDBDRAFT_
XP 636931.1
66806417

Dictyostelium

0187729

discoideum AX4

An enzyme with similar characteristics, alpha-aminoadipate reductase (AAR, EC 1.2.1.31), participates in lysine biosynthesis pathways in some fungal species. This enzyme naturally reduces alpha-aminoadipate to alpha-aminoadipate semialdehyde. The carboxyl group is first activated through the ATP-dependent formation of an adenylate that is then reduced by NAD(P)H to yield the aldehyde and AMP. Like CAR, this enzyme utilizes magnesium and requires activation by a PPTase. Enzyme candidates for AAR and its corresponding PPTase are found in Saccharomyces cerevisiae (Morris et al., Gene 98:141-145 (1991)), Candida albicans (Guo et al., Mol. Genet. Genomics 269:271-279 (2003)), and Schizosaccharomyces pombe (Ford et al., Curr. Genet. 28:131-137 (1995)). The AAR from S. pombe exhibited significant activity when expressed in E. coli (Guo et al., Yeast 21:1279-1288 (2004)). The AAR from Penicillium chrysogenum accepts S-carboxymethyl-L-cysteine as an alternate substrate, but did not react with adipate, L-glutamate or diaminopimelate (Hijarrubia et al., J Biol. Chem. 278:8250-8256 (2003)). The gene encoding the P. chrysogenum PPTase has not been identified to date and no high-confidence hits were identified by sequence comparison homology searching.

Gene
GenBank Accession
GI No.
Organism

LYS2
AAA34747.1
171867

Saccharomyces cerevisiae

LYS5
P50113.1
1708896

Saccharomyces cerevisiae

LYS2
AAC02241.1
2853226

Candida albicans

LYS5
AAO26020.1
28136195

Candida albicans

Lys1p
P40976.3
13124791

Schizosaccharomyces pombe

Lys7p
Q10474.1
1723561

Schizosaccharomyces pombe

Lys2
CAA74300.1
3282044

Penicillium chrysogenum

N) Crotonaldehyde Reductase.

A suitable enzyme activity is provided by an EC 1.1.1.a Oxidoreductase (oxo to alcohol). EC 1.1.1.a Oxidoreductase (oxo to alcohol) includes the following:

The reduction of glutarate semialdehyde to 5-hydroxyvalerate by glutarate semialdehyde reductase entails reduction of an aldehyde to its corresponding alcohol. Enzymes with glutarate semialdehyde reductase activity include the ATEG_00539 gene product of Aspergillus terreus and 4-hydroxybutyrate dehydrogenase of Arabidopsis thaliana, encoded by 4hbd (WO 2010/068953A2). The A. thaliana enzyme was cloned and characterized in yeast (Breitkreuz et al., J. Biol. Chem. 278:41552-41556 (2003)).

PROTEIN
GENBANK ID
GI NUMBER
ORGANISM

ATEG_00539
XP_001210625.1
115491995

Aspergillus

terreus NIH2624

4hbd
AAK94781.1
15375068

Arabidopsis

thaliana

Additional genes encoding enzymes that catalyze the reduction of an aldehyde to alcohol (i.e., alcohol dehydrogenase or equivalently aldehyde reductase) include alrA encoding a medium-chain alcohol dehydrogenase for C2-C14 (Tani et al., Appl. Environ. Microbiol. 66:5231-5235 (2000)), yqhD and fucO from E. coli (Sulzenbacher et al., 342:489-502 (2004)), and bdh I and bdh II from C. acetobutylicum which converts butyraldehyde into butanol (Walter et al., 174:7149-7158 (1992)). YqhD catalyzes the reduction of a wide range of aldehydes using NADPH as the cofactor, with a preference for chain lengths longer than C(3) (Sulzenbacher et al., 342:489-502 (2004); Perez et al., J Biol. Chem. 283:7346-7353 (2008)). The adhA gene product from Zymomonas mobilisE has been demonstrated to have activity on a number of aldehydes including formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and acrolein (Kinoshita et al., Appl Microbiol Biotechnol 22:249-254 (1985)). Additional aldehyde reductase candidates are encoded by bdh in C. saccharoperbutylacetonicum and Cbei_1722, Cbei_2181 and Cbei_2421 in C. Beijerinckii. Additional aldehyde reductase gene candidates in Saccharomyces cerevisiae include the aldehyde reductases GRE3, ALD2-6 and HFD1, glyoxylate reductases GOR1 and YPL113C and glycerol dehydrogenase GCY1 (WO 2011/022651A1; Atsumi et al., Nature 451:86-89 (2008)). The enzyme candidates described previously for catalyzing the reduction of methylglyoxal to acetol or lactaldehyde are also suitable lactaldehyde reductase enzyme candidates.

Protein
GENBANK
GI
ORGANISM

alrA
BAB12273.1
9967138

Acinetobacter sp.

strain M-1

ADH2
NP_014032.1
6323961

Saccharomyces

cerevisiae

yqhD
NP_417484.1
16130909

Escherichia coli

fucO
NP_417279.1
16130706

Escherichia coli

bdh I
NP_349892.1
15896543

Clostridium

acetobutylicum

bdh II
NP_349891.1
15896542

Clostridium

acetobutylicum

adhA
YP_162971.1
56552132

Zymomonas mobilis

bdh
BAF45463.1
124221917

Clostridium

Cbei_1722
YP_001308850
150016596

Clostridium beijerinckii

Cbei_2181
YP_001309304
150017050

Clostridium beijerinckii

Cbei_2421
YP_001309535
150017281

Clostridium beijerinckii

GRE3
P38715.1
731691

Saccharomyces

cerevisiae

ALD2
CAA89806.1
825575

Saccharomyces

cerevisiae

ALD3
NP_013892.1
6323821

Saccharomyces

cerevisiae

ALD4
NP_015019.1
6324950

Saccharomyces

cerevisiae

ALD5
NP_010996.2
330443526

Saccharomyces

cerevisiae

ALD6
ABX39192.1
160415767

Saccharomyces

cerevisiae

HFD1
Q04458.1
2494079

Saccharomyces

cerevisiae

GOR1
NP_014125.1
6324055

Saccharomyces

cerevisiae

YPL113C
AAB68248.1
1163100

Saccharomyces

cerevisiae

GCY1
CAA99318.1
1420317

Saccharomyces

cerevisiae

Enzymes exhibiting 4-hydroxybutyrate dehydrogenase activity (EC 1.1.1.61) also fall into this category. Such enzymes have been characterized in Ralstonia eutropha (Bravo et al., J Forens Sci, 49:379-387 (2004)) and Clostridium kluyveri (Wolff et al., Protein Expr. Purif. 6:206-212 (1995)). Yet another gene is the alcohol dehydrogenase adhI from Geobacillus thermoglucosidasius (Jeon et al., J Biotechnol 135:127-133 (2008)).

PROTEIN
GENBANK ID
GI NUMBER
ORGANISM

4hbd
YP_726053.1
113867564

Ralstonia eutropha H16

4hbd
L21902.1
146348486

Clostridium kluyveri

DSM 555

adhI
AAR91477.1
40795502

Geobacillus

thermoglucosidasius

Another exemplary aldehyde reductase is methylmalonate semialdehyde reductase, also known as 3-hydroxyisobutyrate dehydrogenase (EC 1.1.1.31). This enzyme participates in valine, leucine and isoleucine degradation and has been identified in bacteria, eukaryotes, and mammals. The enzyme encoded by P84067 from Thermus thermophilus HB8 has been structurally characterized (Lokanath et al., J Mol Biol, 352:905-17 (2005)). The reversibility of the human 3-hydroxyisobutyrate dehydrogenase was demonstrated using isotopically-labeled substrate (Manning et al., Biochem J, 231:481-4 (1985)). Additional genes encoding this enzyme include 3hidh in Homo sapiens (Hawes et al., Methods Enzymol, 324:218-228 (2000)) and Oryctolagus cuniculus (Hawes et al., supra; Chowdhury et al., Biosci. Biotechnol Biochem. 60:2043-2047 (1996)), mmsB in Pseudomonas aeruginosa and Pseudomonas putida, and dhat in Pseudomonas putida (Aberhart et al., J Chem. Soc. [Perkin 1] 6:1404-1406 (1979); Chowdhury et al., Biosci. Biotechnol Biochem. 60:2043-2047 (1996); Chowdhury et al., Biosci. Biotechnol Biochem. 67:438-441 (2003)). Several 3-hydroxyisobutyrate dehydrogenase enzymes have been characterized in the reductive direction, including mmsB from Pseudomonas aeruginosa (Gokarn et al., U.S. Pat. No. 739,676, (2008)) and mmsB from Pseudomonas putida.

PROTEIN
GENBANK ID
GI NUMBER
ORGANISM

P84067
P84067
75345323

Thermus thermophilus

3hidh
P31937.2
12643395

Homo sapiens

3hidh
P32185.1
416872

Oryctolagus cuniculus

mmsB
NP_746775.1
26991350

Pseudomonas putida

mmsB
P28811.1
127211

Pseudomonas aeruginosa

dhat
Q59477.1
2842618

Pseudomonas putida

There exist several exemplary alcohol dehydrogenases that convert a ketone to a hydroxyl functional group. Two such enzymes from E. coli are encoded by malate dehydrogenase (mdh) and lactate dehydrogenase (ldhA). In addition, lactate dehydrogenase from Ralstonia eutropha has been shown to demonstrate high activities on 2-ketoacids of various chain lengths including lactate, 2-oxobutyrate, 2-oxopentanoate and 2-oxoglutarate (Steinbuchel et al., Eur. J. Biochem. 130:329-334 (1983)). Conversion of alpha-ketoadipate into alpha-hydroxyadipate can be catalyzed by 2-ketoadipate reductase, an enzyme reported to be found in rat and in human placenta (Suda et al., Arch. Biochem. Biophys. 176:610-620 (1976); Suda et al., Biochem. Biophys. Res. Commun. 77:586-591 (1977)). An additional oxidoreductase is the mitochondrial 3-hydroxybutyrate dehydrogenase (bdh) from the human heart which has been cloned and characterized (Marks et al., J. Biol. Chem. 267:15459-15463 (1992)). Alcohol dehydrogenase enzymes of C. beijerinckii (Ismaiel et al., J. Bacteriol. 175:5097-5105 (1993)) and T. brockii (Lamed et al., Biochem. J. 195:183-190 (1981); Peretz et al., Biochemistry. 28:6549-6555 (1989)) convert acetone to isopropanol. Methyl ethyl ketone reductase catalyzes the reduction of MEK to 2-butanol. Exemplary MEK reductase enzymes can be found in Rhodococcus ruber (Kosjek et al., Biotechnol Bioeng. 86:55-62 (2004)) and Pyrococcus furiosus (van der Oost et al., Eur. J. Biochem. 268:3062-3068 (2001)).

Protein
Genbank ID
GI Number
Organism

mdh
AAC76268.1
1789632

Escherichia coli

ldhA
NP_415898.1
16129341

Escherichia coli

ldh
YP_725182.1
113866693

Ralstonia eutropha

bdh
AAA58352.1
177198

Homo sapiens

adh
AAA23199.2
60592974

Clostridium beijerinckii

NRRL B593

adh
P14941.1
113443

Thermoanaerobacter brockii

HTD4

sadh
CAD36475
21615553

Rhodococcus ruber

adhA
AAC25556
3288810

Pyrococcus furiosus

A number of organisms encode genes that catalyze the reduction of 3-oxobutanol to 1,3-butanediol, including those belonging to the genus Bacillus, Brevibacterium, Candida, and Klebsiella among others, as described by Matsuyama et al. J Mol Cat B Enz, 11:513-521 (2001). One of these enzymes, SADH from Candida parapsilosis, was cloned and characterized in E. coli. A mutated Rhodococcus phenylacetaldehyde reductase (Sar268) and a Leifonia alcohol dehydrogenase have also been shown to catalyze this transformation at high yields (Itoh et al., Appl. Microbiol Biotechnol. 75:1249-1256 (2007)).

Protein
Genbank ID
GI Number
Organism

sadh
BAA24528.1
2815409

Candida parapsilosis

O) Crotyl Alcohol Kinase.

Crotyl alcohol kinase enzymes catalyze the transfer of a phosphate group to the hydroxyl group of crotyl alcohol. The enzymes described below naturally possess such activity or can be engineered to exhibit this activity. Kinases that catalyze transfer of a phosphate group to an alcohol group are members of the EC 2.7.1 enzyme class. The table below lists several useful kinase enzymes in the EC 2.7.1 enzyme class.

Enzyme Commission

Number
Enzyme Name

2.7.1.1
hexokinase

2.7.1.2
glucokinase

2.7.1.3
ketohexokinase

2.7.1.4
fructokinase

2.7.1.5
rhamnulokinase

2.7.1.6
galactokinase

2.7.1.7
mannokinase

2.7.1.8
glucosamine kinase

2.7.1.10
phosphoglucokinase

2.7.1.11
6-phosphofructokinase

2.7.1.12
gluconokinase

2.7.1.13
dehydrogluconokinase

2.7.1.14
sedoheptulokinase

2.7.1.15
ribokinase

2.7.1.16
ribulokinase

2.7.1.17
xylulokinase

2.7.1.18
phosphoribokinase

2.7.1.19
phosphoribulokinase

2.7.1.20
adenosine kinase

2.7.1.21
thymidine kinase

2.7.1.22
ribosylnicotinamide kinase

2.7.1.23
NAD+ kinase

2.7.1.24
dephospho-CoA kinase

2.7.1.25
adenylyl-sulfate kinase

2.7.1.26
riboflavin kinase

2.7.1.27
erythritol kinase

2.7.1.28
triokinase

2.7.1.29
glycerone kinase

2.7.1.30
glycerol kinase

2.7.1.31
glycerate kinase

2.7.1.32
choline kinase

2.7.1.33
pantothenate kinase

2.7.1.34
pantetheine kinase

2.7.1.35
pyridoxal kinase

2.7.1.36
mevalonate kinase

2.7.1.39
homoserine kinase

2.7.1.40
pyruvate kinase

2.7.1.41
glucose-1-phosphate phosphodismutase

2.7.1.42
riboflavin phosphotransferase

2.7.1.43
glucuronokinase

2.7.1.44
galacturonokinase

2.7.1.45
2-dehydro-3-deoxygluconokinase

2.7.1.46
L-arabinokinase

2.7.1.47
D-ribulokinase

2.7.1.48
uridine kinase

2.7.1.49
hydroxymethylpyrimidine kinase

2.7.1.50
hydroxyethylthiazole kinase

2.7.1.51
L-fuculokinase

2.7.1.52
fucokinase

2.7.1.53
L-xylulokinase

2.7.1.54
D-arabinokinase

2.7.1.55
allose kinase

2.7.1.56
1-phosphofructokinase

2.7.1.58
2-dehydro-3-deoxygalactonokinase

2.7.1.59
N-acetylglucosamine kinase

2.7.1.60
N-acylmannosamine kinase

2.7.1.61
acyl-phosphate-hexose phosphotransferase

2.7.1.62
phosphoramidate-hexose phosphotransferase

2.7.1.63
polyphosphate-glucose phosphotransferase

2.7.1.64
inositol 3-kinase

2.7.1.65
scyllo-inosamine 4-kinase

2.7.1.66
undecaprenol kinase

2.7.1.67
1-phosphatidylinositol 4-kinase

2.7.1.68
1-phosphatidylinositol-4-phosphate 5-kinase

2.7.1.69
protein-Np-phosphohistidine-sugar

phosphotransferase

2.7.1.70
identical to EC 2.7.1.37.

2.7.1.71
shikimate kinase

2.7.1.72
streptomycin 6-kinase

2.7.1.73
inosine kinase

2.7.1.74
deoxycytidine kinase

2.7.1.76
deoxyadenosine kinase

2.7.1.77
nucleoside phosphotransferase

2.7.1.78
polynucleotide 5′-hydroxyl-kinase

2.7.1.79
diphosphate-glycerol phosphotransferase

2.7.1.80
diphosphate-serine phosphotransferase

2.7.1.81
hydroxylysine kinase

2.7.1.82
ethanolamine kinase

2.7.1.83
pseudouridine kinase

2.7.1.84
alkylglycerone kinase

2.7.1.85
β-glucoside kinase

2.7.1.86
NADH kinase

2.7.1.87
streptomycin 3″-kinase

2.7.1.88
dihydrostreptomycin-6-phosphate 3′a-kinase

2.7.1.89
thiamine kinase

2.7.1.90
diphosphate-fructose-6-phosphate 1-

phosphotransferase

2.7.1.91
sphinganine kinase

2.7.1.92
5-dehydro-2-deoxygluconokinase

2.7.1.93
alkylglycerol kinase

2.7.1.94
acylglycerol kinase

2.7.1.95
kanamycin kinase

2.7.1.100
S-methyl-5-thioribose kinase

2.7.1.101
tagatose kinase

2.7.1.102
hamamelose kinase

2.7.1.103
viomycin kinase

2.7.1.105
6-phosphofructo-2-kinase

2.7.1.106
glucose-1,6-bisphosphate synthase

2.7.1.107
diacylglycerol kinase

2.7.1.108
dolichol kinase

2.7.1.113
deoxyguanosine kinase

2.7.1.114
AMP-thymidine kinase

2.7.1.118
ADP-thymidine kinase

2.7.1.119
hygromycin-B 7″-O-kinase

2.7.1.121
phosphoenolpyruvate-glycerone

phosphotransferase

2.7.1.122
xylitol kinase

2.7.1.127
inositol-trisphosphate 3-kinase

2.7.1.130
tetraacyldisaccharide 4′-kinase

2.7.1.134
inositol-tetrakisphosphate 1-kinase

2.7.1.136
macrolide 2′-kinase

2.7.1.137
phosphatidylinositol 3-kinase

2.7.1.138
ceramide kinase

2.7.1.140
inositol-tetrakisphosphate 5-kinase

2.7.1.142
glycerol-3-phosphate-glucose phosphotransferase

2.7.1.143
diphosphate-purine nucleoside kinase

2.7.1.144
tagatose-6-phosphate kinase

2.7.1.145
deoxynucleoside kinase

2.7.1.146
ADP-dependent phosphofructokinase

2.7.1.147
ADP-dependent glucokinase

2.7.1.148
4-(cytidine 5′-diphospho)-2-C-methyl-D-

erythritol kinase

2.7.1.149
1-phosphatidylinositol-5-phosphate 4-kinase

2.7.1.150
1-phosphatidylinositol-3-phosphate 5-kinase

2.7.1.151
inositol-polyphosphate multikinase

2.7.1.153
phosphatidylinositol-4,5-bisphosphate 3-kinase

2.7.1.154
phosphatidylinositol-4-phosphate 3-kinase

2.7.1.156
adenosylcobinamide kinase

2.7.1.157
N-acetylgalactosamine kinase

2.7.1.158
inositol-pentakisphosphate 2-kinase

2.7.1.159
inositol-1,3,4-trisphosphate 5/6-kinase

2.7.1.160
2′-phosphotransferase

2.7.1.161
CTP-dependent riboflavin kinase

2.7.1.162
N-acetylhexosamine 1-kinase

2.7.1.163
hygromycin B 4-O-kinase

2.7.1.164
O-phosphoseryl-tRNASec kinase

Mevalonate kinase (EC 2.7.1.36) phosphorylates the terminal hydroxyl group of mevalonate. Gene candidates for this step include erg12 from S. cerevisiae, mvk from Methanocaldococcus jannaschi, MVK from Homo sapeins, and mvk from Arabidopsis thaliana col. Additional mevalonate kinase candidates include the feedback-resistant mevalonate kinase from the archeon Methanosarcina mazei (Primak et al, AEM, in press (2011)) and the Mvk protein from Streptococcus pneumoniae (Andreassi et al, Protein Sci, 16:983-9 (2007)). Mvk proteins from S. cerevisiae, S. pneumoniae and M. mazei were heterologously expressed and characterized in E. coli (Primak et al, supra). The S. pneumoniae mevalonate kinase was active on several alternate substrates including cylopropylmevalonate, vinylmevalonate and ethynylmevalonate (Kudoh et al, Bioorg Med Chem 18:1124-34 (2010)), and a subsequent study determined that the ligand binding site is selective for compact, electron-rich C(3)-substituents (Lefurgy et al, J Biol Chem 285:20654-63 (2010)).

Protein
GenBank ID
GI Number
Organism

erg12
CAA39359.1
3684

Sachharomyces cerevisiae

mvk
Q58487.1
2497517

Methanocaldococcus jannaschii

mvk
AAH16140.1
16359371

Homo sapiens

mvk
NP_851084.1
30690651

Arabidopsis thaliana

mvk
NP_633786.1
21227864

Methanosarcina mazei

mvk
NP_357932.1
15902382

Streptococcus pneumoniae

Glycerol kinase also phosphorylates the terminal hydroxyl group in glycerol to form glycerol-3-phosphate. This reaction occurs in several species, including Escherichia coli, Saccharomyces cerevisiae, and Thermotoga maritima. The E. coli glycerol kinase has been shown to accept alternate substrates such as dihydroxyacetone and glyceraldehyde (Hayashi et al., J Biol. Chem. 242:1030-1035 (1967)). T, maritime has two glycerol kinases (Nelson et al., Nature 399:323-329 (1999)). Glycerol kinases have been shown to have a wide range of substrate specificity. Crans and Whiteside studied glycerol kinases from four different organisms (Escherichia coli, S. cerevisiae, Bacillus stearothermophilus, and Candida mycoderma) (Crans et al., J. Am. Chem. Soc. 107:7008-7018 (2010); Nelson et al., supra, (1999)). They studied 66 different analogs of glycerol and concluded that the enzyme could accept a range of substituents in place of one terminal hydroxyl group and that the hydrogen atom at C2 could be replaced by a methyl group. Interestingly, the kinetic constants of the enzyme from all four organisms were very similar.

Protein
GenBank ID
GI Number
Organism

glpK
AP_003883.1
89110103

Escherichia coli K12

glpK1
NP_228760.1
15642775

Thermotoga maritime MSB8

glpK2
NP_229230.1
15642775

Thermotoga maritime MSB8

Gut1
NP_011831.1
82795252

Saccharomyces cerevisiae

Homoserine kinase is another possible candidate. This enzyme is also present in a number of organisms including E. coli, Streptomyces sp, and S. cerevisiae. Homoserine kinase from E. coli has been shown to have activity on numerous substrates, including, L-2-amino,1,4-butanediol, aspartate semialdehyde, and 2-amino-5-hydroxyvalerate (Huo et al., Biochemistry 35:16180-16185 (1996); Huo et al., Arch. Biochem. Biophys. 330:373-379 (1996)). This enzyme can act on substrates where the carboxyl group at the alpha position has been replaced by an ester or by a hydroxymethyl group. The gene candidates are:

Protein
GenBank ID
GI Number
Organism

thrB
BAB96580.2
85674277

Escherichia coli K12

SACT1DRAFT_4809
ZP_06280784.1
282871792

Streptomyces sp. ACT-

Thr1
AAA35154.1
172978

Saccharomyces

P) 2-Butenyl-4-phosphate Kinase.

2-Butenyl-4-phosphate kinase enzymes catalyze the transfer of a phosphate group to the phosphate group of 2-butenyl-4-phosphate. The enzymes described below naturally possess such activity or can be engineered to exhibit this activity. Kinases that catalyze transfer of a phosphate group to another phosphate group are members of the EC 2.7.4 enzyme class. The table below lists several useful kinase enzymes in the EC 2.7.4 enzyme class.

Enzyme Commission

Number
Enzyme Name

2.7.4.1
polyphosphate kinase

2.7.4.2
phosphomevalonate kinase

2.7.4.3
adenylate kinase

2.7.4.4
nucleoside-phosphate kinase

2.7.4.6
nucleoside-diphosphate kinase

2.7.4.7
phosphomethylpyrimidine kinase

2.7.4.8
guanylate kinase

2.7.4.9
dTMP kinase

2.7.4.10
nucleoside-triphosphate-adenylate kinase

2.7.4.11
(deoxy)adenylate kinase

2.7.4.12
T2-induced deoxynucleotide kinase

2.7.4.13
(deoxy)nucleoside-phosphate kinase

2.7.4.14
cytidylate kinase

2.7.4.15
thiamine-diphosphate kinase

2.7.4.16
thiamine-phosphate kinase

2.7.4.17
3-phosphoglyceroyl-phosphate-polyphosphate

phosphotransferase

2.7.4.18
farnesyl-diphosphate kinase

2.7.4.19
5-methyldeoxycytidine-5′-phosphate

kinase

2.7.4.20
dolichyl-diphosphate-polyphosphate

phosphotransferase

2.7.4.21
inositol-hexakisphosphate kinase

2.7.4.22
UMP kinase

2.7.4.23
ribose 1,5-bisphosphate phosphokinase

2.7.4.24
diphosphoinositol-pentakisphosphate kinase

2.7.4.—
Farnesyl monophosphate kinase

2.7.4.—
Geranyl-geranyl monophosphate kinase

2.7.4.—
Phytyl-phosphate kinase

Phosphomevalonate kinase enzymes are of particular interest. Phosphomevalonate kinase (EC 2.7.4.2) catalyzes the analogous transformation to 2-butenyl-4-phosphate kinase. This enzyme is encoded by erg8 in Saccharomyces cerevisiae (Tsay et al., Mol. Cell Biol. 11:620-631 (1991)) and mvaK2 in Streptococcus pneumoniae, Staphylococcus aureus and Enterococcus faecalis (Doun et al., Protein Sci. 14:1134-1139 (2005); Wilding et al., J Bacteriol. 182:4319-4327 (2000)). The Streptococcus pneumoniae and Enterococcus faecalis enzymes were cloned and characterized in E. coli (Pilloff et al., J Biol. Chem. 278:4510-4515 (2003); Doun et al., Protein Sci. 14:1134-1139 (2005)). The S. pneumoniae phosphomevalonate kinase was active on several alternate substrates including cylopropylmevalonate phosphate, vinylmevalonate phosphate and ethynylmevalonate phosphate (Kudoh et al, Bioorg Med Chem 18:1124-34 (2010)).

Protein
GenBank ID
GI Number
Organism

Erg8
AAA34596.1
171479

Saccharomyces cerevisiae

mvaK2
AAG02426.1
9937366

Staphylococcus aureus

mvaK2
AAG02457.1
9937409

Streptococcus pneumoniae

mvaK2
AAG02442.1
9937388

Enterococcus faecalis

Farnesyl monophosphate kinase enzymes catalyze the CTP dependent phosphorylation of farnesyl monophosphate to farnesyl diphosphate. Similarly, geranylgeranyl phosphate kinase catalyzes CTP dependent phosphorylation. Enzymes with these activities were identified in the microsomal fraction of cultured Nicotiana tabacum (Thai et al, PNAS 96:13080-5 (1999)). However, the associated genes have not been identified to date.

Q) Butadiene Synthase.

Butadiene synthase catalyzes the conversion of 2-butenyl-4-diphosphate to 1,3-butadiene. The enzymes described below naturally possess such activity or can be engineered to exhibit this activity. Carbon-oxygen lyases that operate on phosphates are found in the EC 4.2.3 enzyme class. The table below lists several useful enzymes in EC class 4.2.3.

Enzyme Commission

Number
Enzyme Name

4.2.3.15
Myrcene synthase

4.2.3.26
Linalool synthase

4.2.3.27
Isoprene synthase

4.2.3.36
Terpentriene sythase

4.2.3.46
(E,E)-alpha-Farnesene synthase

4.2.3.47
Beta-Farnesene synthase

4.2.3.49
Nerolidol synthase

Particularly useful enzymes include isoprene synthase, myrcene synthase and farnesene synthase. Enzyme candidates are described below.

Isoprene synthase naturally catalyzes the conversion of dimethylallyl diphosphate to isoprene, but can also catalyze the synthesis of 1,3-butadiene from 2-butenyl-4-diphosphate. Isoprene synthases can be found in several organisms including Populus alba (Sasaki et al., FEBS Letters, 2005, 579 (11), 2514-2518), Pueraria montana (Lindberg et al., Metabolic Eng, 12(1):70-79 (2010); Sharkey et al., Plant Physiol., 137(2):700-712 (2005)), and Populus tremula×Populus alba, also called Populus canescens (Miller et al., Planta, 2001, 213 (3), 483-487). The crystal structure of the Populus canescens isoprene synthase was determined (Koksal et al, J Mol Biol 402:363-373 (2010)). Additional isoprene synthase enzymes are described in (Chotani et al., WO/2010/031079, Systems Using Cell Culture for Production of Isoprene; Cervin et al., US Patent Application 20100003716, Isoprene Synthase Variants for Improved Microbial Production of Isoprene).

Protein
GenBank ID
GI
Organism

ispS
BAD98243.1
63108310

Populus alba

ispS
AAQ84170.1
35187004

Pueraria montana

ispS
CAC35696.1
13539551

Populus tremula × Populus alba

Myrcene synthase enzymes catalyze the dephosphorylation of geranyl diphosphate to beta-myrcene (EC 4.2.3.15). Exemplary myrcene synthases are encoded by MST2 of Solanum lycopersicum (van Schie et al, Plant Mol Biol 64:D473-79 (2007)), TPS-Myr of Picea abies (Martin et al, Plant Physiol 135:1908-27 (2004)) g-myr of Abies grandis (Bohlmann et al, J Biol Chem 272:21784-92 (1997)) and TPS10 of Arabidopsis thaliana (Bohlmann et al, Arch Biochem Biophys 375:261-9 (2000)). These enzymes were heterologously expressed in E. coli.

Protein
GenBank ID
GI Number
Organism

MST2
ACN58229.1
224579303

Solarium lycopersicum

TPS-Myr
AAS47690.2
77546864

Picea abies

G-myr
O24474.1
17367921

Abies grandis

TPS10
EC07543.1
330252449

Arabidopsis thaliana

Farnesyl diphosphate is converted to alpha-farnesene and beta-farnesene by alpha-farnesene synthase and beta-farnesene synthase, respectively. Exemplary alpha-farnesene synthase enzymes include TPS03 and TPS02 of Arabidopsis thaliana (Faldt et al, Planta 216:745-51 (2003); Huang et al, Plant Physiol 153:1293-310 (2010)), afs of Cucumis sativus (Mercke et al, Plant Physiol 135:2012-14 (2004), eafar of Malus×domestica (Green et al, Phytochem 68:176-88 (2007)) and TPS-Far of Picea abies (Martin, supra). An exemplary beta-farnesene synthase enzyme is encoded by TPS1 of Zea mays (Schnee et al, Plant Physiol 130:2049-60 (2002)).

Protein
GenBank ID
GI Number
Organism

TPS03
A4FVP2.1
205829248

Arabidopsis thaliana

TPS02
P0CJ43.1
317411866

Arabidopsis thaliana

TPS-Far
AAS47697.1
44804601

Picea abies

afs
AAU05951.1
51537953

Cucumis sativus

eafar
Q84LB2.2
75241161

Malus × domestica

TPS1
Q84ZW8.1
75149279

Zea mays

R) Crotyl Alcohol Diphosphokinase.

Crotyl alcohol diphosphokinase enzymes catalyze the transfer of a diphosphate group to the hydroxyl group of crotyl alcohol. The enzymes described below naturally possess such activity or can be engineered to exhibit this activity. Kinases that catalyze transfer of a diphosphate group are members of the EC 2.7.6 enzyme class. The table below lists several useful kinase enzymes in the EC 2.7.6 enzyme class.

Enzyme Commission

Number
Enzyme Name

2.7.6.1
ribose-phosphate diphosphokinase

2.7.6.2
thiamine diphosphokinase

2.7.6.3
2-amino-4-hydroxy-6-hydroxymethyldi-

hydropteridine diphosphokinase

2.7.6.4
nucleotide diphosphokinase

2.7.6.5
GTP diphosphokinase

Of particular interest are ribose-phosphate diphosphokinase enzymes which have been identified in Escherichia coli (Hove-Jenson et al., J Biol Chem, 1986, 261(15); 6765-71) and Mycoplasma pneumoniae M129 (McElwain et al, International Journal of Systematic Bacteriology, 1988, 38:417-423) as well as thiamine diphosphokinase enzymes. Exemplary thiamine diphosphokinase enzymes are found in Arabidopsis thaliana (Ajjawi, Plant Mol Biol, 2007, 65(1-2); 151-62).

Protein
GenBank ID
GI Number
Organism

prs
NP_415725.1
16129170

Escherichia coli

prsA
NP_109761.1
13507812

Mycoplasma pneumoniae

M129

TPK1
BAH19964.1
222424006

Arabidopsis thaliana col

TPK2
BAH57065.1
227204427

Arabidopsis thaliana col

S) Chemical Dehydration or Crotyl Alcohol Dehydratase.

Converting crotyl alcohol to butadiene using a crotyl alcohol dehydratase can include combining the activities of the enzymatic isomerization of crotyl alcohol to 3-buten-2-ol then dehydration of 3-buten-2-ol to butadiene. An exemplary bifunctional enzyme with isomerase and dehydratase activities is the linalool dehydratase/isomerase of Castellaniella defragrans. This enzyme catalyzes the isomerization of geraniol to linalool and the dehydration of linalool to myrcene, reactants similar in structure to crotyl alcohol, 3-buten-2-ol and butadiene (Brodkorb et al, J Biol Chem 285:30436-42 (2010)). Enzyme accession numbers and homologs are listed in the table below.

Protein
GenBank ID
GI Number
Organism

Ldi
E1XUJ2.1
403399445

Castellaniella

defragrans

STEHIDRAFT_68678
EIM80109.1
389738914

Stereum hirsutum FP-

91666 SS1

NECHADRAFT_82460
XP_003040778.1
302883759

Nectria

haematococca mpVI

77-13-4

AS9A_2751
YP_004493998.1
333920417

Amycolicicoccus

subflavus DQS3-9A1

Alternatively, a fusion protein or protein conjugate can be generated using well know methods in the art to generate a bi-functional (dual-functional) enzyme having both the isomerase and dehydratase activities. The fusion protein or protein conjugate can include at least the active domains of the enzymes (or respective genes) of the isomerase and dehydratase reactions. For the first step, the conversion of crotyl alcohol to 3-buten-2-ol, enzymatic conversion can be catalyzed by a crotyl alcohol isomerase (classified as EC 5.4.4). A similar isomerization, the conversion of 2-methyl-3-buten-2-ol to 3-methyl-2-buten-1-ol, is catalyzed by cell extracts of Pseudomonas putida MB-1 (Malone et al, AEM 65 (6): 2622-30 (1999)). The extract may be used in vitro, or the protein or gene(s) associated with the isomerase activity can be isolated and used, even though they have not been identified to date. Alternatively, either or both steps can be done by chemical conversion, or by enzymatic conversion (in vivo or in vitro), or any combination. Enzymes having the desired activity for the conversion of 3-buten-2-ol to butadiene are provided elsewhere herein.

T) Butadiene Synthase (Monophosphate).

Butadiene synthase (monophosphate) catalyzes the conversion of 2-butenyl-4-phosphate to 1,3-butadiene. Butadiene synthase enzymes are of the EC 4.2.3 enzyme class as described herein that possess such activity or can be engineered to exhibit this activity. Diphosphate lyase enzymes catalyze the conversion of alkyl diphosphates to alkenes. Carbon-oxygen lyases that operate on phosphates are found in the EC 4.2.3 enzyme class. The table below lists several useful enzymes in EC class 4.2.3. Exemplary enzyme candidates are also phosphate lyases.

Enzyme Commission No.
Enzyme Name

4.2.3.5
Chorismate synthase

4.2.3.15
Myrcene synthase

4.2.3.27
Isoprene synthase

4.2.3.36
Terpentriene sythase

4.2.3.46
(E,E)-alpha-Farnesene synthase

4.2.3.47
Beta-Farnesene synthase

Phosphate lyase enzymes catalyze the conversion of alkyl phosphates to alkenes. Carbon-oxygen lyases that operate on phosphates are found in the EC 4.2.3 enzyme class. The table below lists several relevant enzymes in EC class 4.2.3.

Enzyme Commission

Number
Enzyme Name

4.2.3.5
Chorismate synthase

4.2.3.15
Myrcene synthase

4.2.3.26
Linalool synthase

4.2.3.27
Isoprene synthase

4.2.3.36
Terpentriene sythase

4.2.3.46
(E,E)-alpha-Farnesene synthase

4.2.3.47
Beta-Farnesene synthase

4.2.3.49
Nerolidol synthase

4.2.3.—
Methylbutenol synthase

Isoprene synthase enzymes catalyzes the conversion of dimethylallyl diphosphate to isoprene. Isoprene synthases can be found in several organisms including Populus alba (Sasaki et al., FEBS Letters, 2005, 579 (11), 2514-2518), Pueraria montana (Lindberg et al., Metabolic Eng, 12(1):70-79 (2010); Sharkey et al., Plant Physiol., 137(2):700-712 (2005)), and Populus tremula×Populus alba, also called Populus canescens (Miller et al., Planta, 2001, 213 (3), 483-487). The crystal structure of the Populus canescens isoprene synthase was determined (Koksal et al, J Mol Biol 402:363-373 (2010)). Additional isoprene synthase enzymes are described in (Chotani et al., WO/2010/031079, Systems Using Cell Culture for Production of Isoprene; Cervin et al., US Patent Application 20100003716, Isoprene Synthase Variants for Improved Microbial Production of Isoprene). Another isoprene synthase-like enzyme from Pinus sabiniana, methylbutenol synthase, catalyzes the formation of 2-methyl-3-buten-2-ol (Grey et al, J Biol Chem 286: 20582-90 (2011)).

Protein
GenBank ID
GI Number
Organism

ispS
BAD98243.1
63108310

Populus alba

ispS
AAQ84170.1
35187004

Pueraria montana

ispS
CAC35696.1
13539551

Populus tremula ×

Populus alba

Tps-MBO1
AEB53064.1
328834891

Pinus sabiniana

Chorismate synthase (EC 4.2.3.5) participates in the shikimate pathway, catalyzing the dephosphorylation of 5-enolpyruvylshikimate-3-phosphate to chorismate. The enzyme requires reduced flavin mononucleotide (FMN) as a cofactor, although the net reaction of the enzyme does not involve a redox change. In contrast to the enzyme found in plants and bacteria, the chorismate synthase in fungi is also able to reduce FMN at the expense of NADPH (Macheroux et al., Planta 207:325-334 (1999)). Representative monofunctional enzymes are encoded by aroC of E. coli (White et al., Biochem. J. 251:313-322 (1988)) and Streptococcus pneumoniae (Maclean and Ali, Structure 11:1499-1511 (2003)). Bifunctional fungal enzymes are found in Neurospora crassa (Kitzing et al., J. Biol. Chem. 276:42658-42666 (2001)) and Saccharomyces cerevisiae (Jones et al., Mol. Microbiol. 5:2143-2152 (1991)).

GenBank

Gene
Accession No.
GI No.
Organism

aroC
NP_416832.1
16130264

Escherichia coli

aroC
ACH47980.1
197205483

Streptococcus

U25818.1:19 . . .
AAC49056.1
976375

Neurospora crassa

1317

ARO2
CAA42745.1
3387

Saccharomyces

cerevisiae

Protein
GenBank ID
GI Number
Organism

MST2
ACN58229.1
224579303

Solanum lycopersicum

TPS-Myr
AAS47690.2
77546864

Picea abies

G-myr
O24474.1
17367921

Abies grandis

TPS10
EC07543.1
330252449

Arabidopsis thaliana

U) Crotonyl-CoA Reductase (Alcohol Forming) and V) 3-Hydroxybutyryl-CoA Reductase (Alcohol Forming).

The direct conversion of crotonyl-CoA and 3-hydroxybutyryl-CoA substrates to their corresponding alcohols is catalyzed by bifuncitonal enzymes with acyl-CoA reductase (aldehyde forming) activity and aldehyde reductase or alcohol dehydrogenase activities. Exemplary bifunctional oxidoreductases that convert an acyl-CoA to alcohol are described elsewhere herein. FIG. 6 shows pathways for converting 1,3-butanediol to 3-buten-2-ol and/or butadiene. Enzymes in FIG. 6 are A. 1,3-butanediol kinase, B. 3-hydroxybutyrylphosphate kinase, C. 3-hydroxybutyryldiphosphate lyase, D. 1,3-butanediol diphosphokinase, E. 1,3-butanediol dehydratase, F. 3-hydroxybutyrylphosphate lyase, G. 3-buten-2-ol dehydratase or chemical reaction.

A. 1,3-Butanediol Kinase.

Phosphorylation of 1,3-butanediol to 3-hydroxybutyrylphosphate is catalyzed by an alcohol kinase enzyme. Alcohol kinase enzymes catalyze the transfer of a phosphate group to a hydroxyl group. Kinases that catalyze transfer of a phosphate group to an alcohol group are members of the EC 2.7.1 enzyme class. The table below lists several useful kinase enzymes in the EC 2.7.1 enzyme class.

Enzyme Commission

Number
Enzyme Name

2.7.1.1
hexokinase

2.7.1.2
glucokinase

2.7.1.3
ketohexokinase

2.7.1.4
fructokinase

2.7.1.5
rhamnulokinase

2.7.1.6
galactokinase

2.7.1.7
mannokinase

2.7.1.8
glucosamine kinase

2.7.1.10
phosphoglucokinase

2.7.1.11
6-phosphofructokinase

2.7.1.12
gluconokinase

2.7.1.13
dehydrogluconokinase

2.7.1.14
sedoheptulokinase

2.7.1.15
ribokinase

2.7.1.16
ribulokinase

2.7.1.17
xylulokinase

2.7.1.18
phosphoribokinase

2.7.1.19
phosphoribulokinase

2.7.1.20
adenosine kinase

2.7.1.21
thymidine kinase

2.7.1.22
ribosylnicotinamide kinase

2.7.1.23
NAD+ kinase

2.7.1.24
dephospho-CoA kinase

2.7.1.25
adenylyl-sulfate kinase

2.7.1.26
riboflavin kinase

2.7.1.27
erythritol kinase

2.7.1.28
triokinase

2.7.1.29
glycerone kinase

2.7.1.30
glycerol kinase

2.7.1.31
glycerate kinase

2.7.1.32
choline kinase

2.7.1.33
pantothenate kinase

2.7.1.34
pantetheine kinase

2.7.1.35
pyridoxal kinase

2.7.1.36
mevalonate kinase

2.7.1.39
homoserine kinase

2.7.1.40
pyruvate kinase

2.7.1.41
glucose-1-phosphate phosphodismutase

2.7.1.42
riboflavin phosphotransferase

2.7.1.43
glucuronokinase

2.7.1.44
galacturonokinase

2.7.1.45
2-dehydro-3-deoxygluconokinase

2.7.1.46
L-arabinokinase

2.7.1.47
D-ribulokinase

2.7.1.48
uridine kinase

2.7.1.49
hydroxymethylpyrimidine kinase

2.7.1.50
hydroxyethylthiazole kinase

2.7.1.51
L-fuculokinase

2.7.1.52
fucokinase

2.7.1.53
L-xylulokinase

2.7.1.54
D-arabinokinase

2.7.1.55
allose kinase

2.7.1.56
1-phosphofructokinase

2.7.1.58
2-dehydro-3-deoxygalactonokinase

2.7.1.59
N-acetylglucosamine kinase

2.7.1.60
N-acylmannosamine kinase

2.7.1.61
acyl-phosphate-hexose phosphotransferase

2.7.1.62
phosphoramidate-hexose phosphotransferase

2.7.1.63
polyphosphate-glucose phosphotransferase

2.7.1.64
inositol 3-kinase

2.7.1.65
scyllo-inosamine 4-kinase

2.7.1.66
undecaprenol kinase

2.7.1.67
1-phosphatidylinositol 4-kinase

2.7.1.68
1-phosphatidylinositol-4-phosphate 5-kinase

2.7.1.69
protein-Np-phosphohistidine-sugar

phosphotransferase

2.7.1.70
identical to EC 2.7.1.37.

2.7.1.71
shikimate kinase

2.7.1.72
streptomycin 6-kinase

2.7.1.73
inosine kinase

2.7.1.74
deoxycytidine kinase

2.7.1.76
deoxyadenosine kinase

2.7.1.77
nucleoside phosphotransferase

2.7.1.78
polynucleotide 5′-hydroxyl-kinase

2.7.1.79
diphosphate-glycerol phosphotransferase

2.7.1.80
diphosphate-serine phosphotransferase

2.7.1.81
hydroxylysine kinase

2.7.1.82
ethanolamine kinase

2.7.1.83
pseudouridine kinase

2.7.1.84
alkylglycerone kinase

2.7.1.85
β-glucoside kinase

2.7.1.86
NADH kinase

2.7.1.87
streptomycin 3″-kinase

2.7.1.88
dihydrostreptomycin-6-phosphate 3′a-kinase

2.7.1.89
thiamine kinase

2.7.1.90
diphosphate-fructose-6-phosphate 1-

phosphotransferase

2.7.1.91
sphinganine kinase

2.7.1.92
5-dehydro-2-deoxygluconokinase

2.7.1.93
alkylglycerol kinase

2.7.1.94
acylglycerol kinase

2.7.1.95
kanamycin kinase

2.7.1.100
S-methyl-5-thioribose kinase

2.7.1.101
tagatose kinase

2.7.1.102
hamamelose kinase

2.7.1.103
viomycin kinase

2.7.1.105
6-phosphofructo-2-kinase

2.7.1.106
glucose-1,6-bisphosphate synthase

2.7.1.107
diacylglycerol kinase

2.7.1.108
dolichol kinase

2.7.1.113
deoxyguanosine kinase

2.7.1.114
AMP-thymidine kinase

2.7.1.118
ADP-thymidine kinase

2.7.1.119
hygromycin-B 7″-O-kinase

2.7.1.121
phosphoenolpyruvate-glycerone

phosphotransferase

2.7.1.122
xylitol kinase

2.7.1.127
inositol-trisphosphate 3-kinase

2.7.1.130
tetraacyldisaccharide 4′-kinase

2.7.1.134
inositol-tetrakisphosphate 1-kinase

2.7.1.136
macrolide 2′-kinase

2.7.1.137
phosphatidylinositol 3-kinase

2.7.1.138
ceramide kinase

2.7.1.140
inositol-tetrakisphosphate 5-kinase

2.7.1.142
glycerol-3-phosphate-glucose

phosphotransferase

2.7.1.143
diphosphate-purine nucleoside kinase

2.7.1.144
tagatose-6-phosphate kinase

2.7.1.145
deoxynucleoside kinase

2.7.1.146
ADP-dependent phosphofructokinase

2.7.1.147
ADP-dependent glucokinase

2.7.1.148
4-(cytidine 5′-diphospho)-2-C-methyl-D-

erythritol kinase

2.7.1.149
1-phosphatidylinositol-5-phosphate 4-kinase

2.7.1.150
1-phosphatidylinositol-3-phosphate 5-kinase

2.7.1.151
inositol-polyphosphate multikinase

2.7.1.153
phosphatidylinositol-4,5-bisphosphate 3-kinase

2.7.1.154
phosphatidylinositol-4-phosphate 3-kinase

2.7.1.156
adenosylcobinamide kinase

2.7.1.157
N-acetylgalactosamine kinase

2.7.1.158
inositol-pentakisphosphate 2-kinase

2.7.1.159
inositol-1,3,4-trisphosphate 5/6-kinase

2.7.1.160
2′-phosphotransferase

2.7.1.161
CTP-dependent riboflavin kinase

2.7.1.162
N-acetylhexosamine 1-kinase

2.7.1.163
hygromycin B 4-O-kinase

2.7.1.164
O-phosphoseryl-tRNASec kinase

Glycerol kinase also phosphorylates the terminal hydroxyl group in glycerol to form glycerol-3-phosphate. This reaction occurs in several species, including Escherichia coli, Saccharomyces cerevisiae, and Thermotoga maritima. The E. coli glycerol kinase has been shown to accept alternate substrates such as dihydroxyacetone and glyceraldehyde (Hayashi et al., J Biol. Chem. 242:1030-1035 (1967)). T. maritime has two glycerol kinases (Nelson et al., Nature 399:323-329 (1999)). Glycerol kinases have been shown to have a wide range of substrate specificity. Crans and Whiteside studied glycerol kinases from four different organisms (Escherichia coli, S. cerevisiae, Bacillus stearothermophilus, and Candida mycoderma) (Crans et al., J. Am. Chem. Soc. 107:7008-7018 (2010); Nelson et al., supra, (1999)). They studied 66 different analogs of glycerol and concluded that the enzyme could accept a range of substituents in place of one terminal hydroxyl group and that the hydrogen atom at C2 could be replaced by a methyl group. Interestingly, the kinetic constants of the enzyme from all four organisms were very similar.

Protein
GenBank ID
GI Number
Organism

glpK
AP_003883.1
89110103

Escherichia coli K12

glpK1
NP_228760.1
15642775

Thermotoga maritime

glpK2
NP_229230.1
15642775

Thermotoga maritime

Gut1
NP_011831.1
82795252

Saccaromyces
cerevisiae

Homoserine kinase is another similar enzyme candidate. This enzyme is also present in a number of organisms including E. coli, Streptomyces sp, and S. cerevisiae. Homoserine kinase from E. coli has been shown to have activity on numerous substrates, including, L-2-amino,1,4-butanediol, aspartate semialdehyde, and 2-amino-5-hydroxyvalerate (Huo et al., Biochemistry 35:16180-16185 (1996); Huo et al., Arch. Biochem. Biophys. 330:373-379 (1996)). This enzyme can act on substrates where the carboxyl group at the alpha position has been replaced by an ester or by a hydroxymethyl group. The gene candidates are:

Protein
GenBank ID
GI Number
Organism

thrB
BAB96580.2
85674277

Escherichia coli K12

SACT1DRAFT_4809
ZP_06280784.1
282871792

Streptomyces sp. ACT-

Thr1
AAA35154.1
172978

Saccharomyces

B. 3-Hydroxybutyrylphosphate Kinase.

Alkyl phosphate kinase enzymes catalyze the transfer of a phosphate group to the phosphate group of an alkyl phosphate. The enzymes described below naturally possess such activity or can be engineered to exhibit this activity. Kinases that catalyze transfer of a phosphate group to another phosphate group are members of the EC 2.7.4 enzyme class. The table below lists several useful kinase enzymes in the EC 2.7.4 enzyme class.

Enzyme Commission No.
Enzyme Name

2.7.4.1
polyphosphate kinase

2.7.4.2
phosphomevalonate kinase

2.7.4.3
adenylate kinase

2.7.4.4
nucleoside-phosphate kinase

2.7.4.6
nucleoside-diphosphate kinase

2.7.4.7
phosphomethylpyrimidine kinase

2.7.4.8
guanylate kinase

2.7.4.9
dTMP kinase

2.7.4.10
nucleoside-triphosphate-adenylate kinase

2.7.4.11
(deoxy)adenylate kinase

2.7.4.12
T2-induced deoxynucleotide kinase

2.7.4.13
(deoxy)nucleoside-phosphate kinase

2.7.4.14
cytidylate kinase

2.7.4.15
thiamine-diphosphate kinase

2.7.4.16
thiamine-phosphate kinase

2.7.4.17
3-phosphoglyceroyl-phosphate-polyphosphate

phosphotransferase

2.7.4.18
farnesyl-diphosphate kinase

2.7.4.19
5-methyldeoxycytidine-5′-phosphate kinase

2.7.4.20
dolichyl-diphosphate-polyphosphate

phosphotransferase

2.7.4.21
inositol-hexakisphosphate kinase

2.7.4.22
UMP kinase

2.7.4.23
ribose 1,5-bisphosphate phosphokinase

2.7.4.24
diphosphoinositol-pentakisphosphate kinase

2.7.4.—
Farnesyl monophosphate kinase

2.7.4.—
Geranyl-geranyl monophosphate kinase

2.7.4.—
Phytyl-phosphate kinase

Phosphomevalonate kinase enzymes are of particular interest. Phosphomevalonate kinase (EC 2.7.4.2) catalyzes the phosphorylation of phosphomevalonate. This enzyme is encoded by erg8 in Saccharomyces cerevisiae (Tsay et al., Mol. Cell Biol. 11:620-631 (1991)) and mvaK2 in Streptococcus pneumoniae, Staphylococcus aureus and Enterococcus faecalis (Doun et al., Protein Sci. 14:1134-1139 (2005); Wilding et al., J Bacteriol. 182:4319-4327 (2000)). The Streptococcus pneumoniae and Enterococcus faecalis enzymes were cloned and characterized in E. coli (Pilloff et al., J Biol. Chem. 278:4510-4515 (2003); Doun et al., Protein Sci. 14:1134-1139 (2005)). The S. pneumoniae phosphomevalonate kinase was active on several alternate substrates including cylopropylmevalonate phosphate, vinylmevalonate phosphate and ethynylmevalonate phosphate (Kudoh et al, Bioorg Med Chem 18:1124-34 (2010)).

Farnesyl monophosphate kinase enzymes catalyze the CTP dependent phosphorylation of farnesyl monophosphate to farnesyl diphosphate. Similarly, geranylgeranyl phosphate kinase catalyzes CTP dependent phosphorylation. Enzymes with these activities were identified in the microsomal fraction of cultured Nicotiana tabacum (Thai et al, PNAS 96:13080-5 (1999)). However, the associated genes have not been identified to date.

C. 3-Hydroxybutyryldiphosphate Lyase.

Diphosphate lyase enzymes catalyze the conversion of alkyl diphosphates to alkenes. Carbon-oxygen lyases that operate on phosphates are found in the EC 4.2.3 enzyme class. The table below lists several useful enzymes in EC class 4.2.3. described herein. Exemplary enzyme candidates also include phosphate lyases described herein.

Enzyme

Commission

No.
Enzyme Name

4.2.3.5
Chorismate synthase

4.2.3.15
Myrcene synthase

4.2.3.27
Isoprene synthase

4.2.3.36
Terpentriene sythase

4.2.3.46
(E, E)-alpha-Farnesene synthase

4.2.3.47
Beta-Farnesene synthase

D. 1,3-Butanediol Dehydratase.

Exemplary dehydratase enzymes suitable for dehydrating 1,3-butanediol to 3-buten-2-ol include oleate hydratases, acyclic 1,2-hydratases and linalool dehydratase. Exemplary enzyme candidates are described above.

E. 1,3-Butanediol Diphosphokinase.

Diphosphokinase enzymes catalyze the transfer of a diphosphate group to an alcohol group. The enzymes described below naturally possess such activity. Kinases that catalyze transfer of a diphosphate group are members of the EC 2.7.6 enzyme class. The table below lists several useful kinase enzymes in the EC 2.7.6 enzyme class.

Enzyme

Commission

No.
Enzyme Name

2.7.6.1
ribose-phosphate diphosphokinase

2.7.6.2
thiamine diphosphokinase

2-amino-4-hydroxy-6-

2.7.6.3
hydroxymethyldihydropteridine

diphosphokinase

2.7.6.4
nucleotide diphosphokinase

2.7.6.5
GTP diphosphokinase

Of particular interest are ribose-phosphate diphosphokinase enzymes, which have been identified in Escherichia coli (Hove-Jenson et al., J Biol Chem, 1986, 261(15); 6765-71) and Mycoplasma pneumoniae M129 (McElwain et al, International Journal of Systematic Bacteriology, 1988, 38:417-423) as well as thiamine diphosphokinase enzymes. Exemplary thiamine diphosphokinase enzymes are found in Arabidopsis thaliana (Ajjawi, Plant Mol Biol, 2007, 65(1-2); 151-62).

Protein
GenBank ID
GI Number
Organism

prs
NP_415725.1
16129170

Escherichia coli

prsA
NP_109761.1
13507812

Mycoplasma pneumoniae M129

TPK1
BAH19964.1
222424006

Arabidopsis thaliana col

TPK2
BAH57065.1
227204427

Arabidopsis thaliana col

F. 3-Hydroxybutyrylphosphate Lyase.

Enzyme

Commission

Number
Enzyme Name

4.2.3.5
Chorismate synthase

4.2.3.15
Myrcene synthase

4.2.3.26
Linalool synthase

4.2.3.27
Isoprene synthase

4.2.3.36
Terpentriene sythase

4.2.3.46
(E, E)-alpha-Farnesene synthase

4.2.3.47
Beta-Farnesene synthase

4.2.3.49
Nerolidol synthase

4.2.3.-
Methylbutenol synthase

Protein
GenBank ID
GI Number
Organism

ispS
BAD98243.1
63108310

Populus alba

ispS
AAQ84170.1
35187004

Pueraria montana

ispS
CAC35696.1
13539551

Populus tremula x

Populus alba

Tps-MBO1
AEB53064.1
328834891

Pinus sabiniana

Gene
GenBank
GI No.
Organism

aroC
NP_416832.1
16130264

Escherichia coli

aroC
ACH47980.1
197205483

Streptococcus

U25818.1:
AAC49056.1
976375

Neurospora crassa

19..1317

ARO2
CAA42745.1
3387

Saccharomyces

G. G. 3-Buten-2-ol Dehydratase.

Dehydration of 3-buten-2-ol to butadiene is catalyzed by a 3-buten-2-ol dehydratase enzyme or by chemical dehydration. Exemplary dehydratase enzymes suitable for dehydrating 3-buten-2-ol include oleate hydratase, acyclic 1,2-hydratase and linalool dehydratase enzymes. Exemplary enzymes are described above.

Example XI
1,4-Butanediol Synthesis Enzymes

This Example provides genes that can be used for conversion of succinyl-CoA to 1,4-butanediol as depicted in the pathways of FIG. 7.

FIG. 7. depicts A) a succinyl-CoA transferase or a succinyl-CoA synthetase, B) a succinyl-CoA reductase (aldehyde forming), C) a 4-HB dehydrogenase, D) a 4-HB kinase, E) a phosphotrans-4-hydroxybutyrylase, F) a 4-hydroxybutyryl-CoA reductase (aldehyde forming), G) a 1,4-butanediol dehydrogenase, H) a succinate reductase, I) a succinyl-CoA reductase (alcohol forming), J) a 4-hydroxybutyryl-CoA transferase or 4-hydroxybutyryl-CoA synthetase, K) a 4-HB reductase, L) a 4-hydroxybutyryl-phosphate reductase, and M) a 4-hydroxybutyryl-CoA reductase (alcohol forming).

A) Succinyl-CoA Transferase (Designated as EB1) or Succinyl-CoA Synthetase (Designated as EB2A).

The conversion of succinate to succinyl-CoA is catalyzed by EB1 or EB2A (synthetase or ligase). Exemplary EB1 and EB2A enzymes are described above.

b) succinyl-CoA Reductase (Aldehyde Forming).

Enzymes with succinyl-CoA reductase activity are encoded by sucD of Clostridium kluyveri (Sohling, J. Bacteriol. 178:871-880 (1996)) and sucD of Porphyromonas gingivalis (Takahashi, J. Bacteriol 182:4704-4710 (2000)). Additional succinyl-CoA reductase enzymes participate in the 3-hydroxypropionate/4-HB cycle of thermophilic archaea such as Metallosphaera sedula (Berg et al., Science 318:1782-1786 (2007)) and Thermoproteus neutrophilus (Ramos-Vera et al., J Bacteriol, 191:4286-4297 (2009)). These and other exemplary succinyl-CoA reductase enzymes are described above.

C) 4-HB Dehydrogenase (Designated as EB4).

Enzymes exhibiting EB4 activity (EC 1.1.1.61) have been characterized in Ralstonia eutropha (Bravo et al., J. Forensic Sci. 49:379-387 (2004), Clostridium kluyveri (Wolff and Kenealy, Protein Expr. Purif. 6:206-212 (1995)) and Arabidopsis thaliana (Breitkreuz et al., J. Biol. Chem. 278:41552-41556 (2003)). Other EB4 enzymes are found in Porphyromonas gingivalis and gbd of an uncultured bacterium. Accession numbers of these genes are listed in the table below.

Protein
GenBank ID
GI Number
Organism

4hbd
YP_726053.1
113867564

Ralstonia eutropha H16

4hbd
L21902.1
146348486

Clostridium kluyveri DSM

555

4hbd
Q94B07
75249805

Arabidopsis thaliana

4-hBd
NP_904964.1
34540485

Porphyromonas gingivalis

W83

gbd
AF148264.1
5916168
Uncultured bacterium

D) 4-HB Kinase (Designated as EB5).

Activation of 4-HB to 4-hydroxybutyryl-phosphate is catalyzed by EB5. Phosphotransferase enzymes in the EC class 2.7.2 transform carboxylic acids to phosphonic acids with concurrent hydrolysis of one ATP. Enzymes suitable for catalyzing this reaction include butyrate kinase, acetate kinase, aspartokinase and gamma-glutamyl kinase. Butyrate kinase carries out the reversible conversion of butyryl-phosphate to butyrate during acidogenesis in C. acetobutylicum (Cary et al., Appl. Environ. Microbiol. 56:1576-1583 (1990)). This enzyme is encoded by either of the two buk gene products (Huang et al., J. Mol. Microbiol. Biotechnol. 2:33-38 (2000)). Other butyrate kinase enzymes are found in C. butyricum, C. beijerinckii and C. tetanomorphum (Twarog and Wolfe, J. Bacteriol. 86:112-117 (1963)). A related enzyme, isobutyrate kinase from Thermotoga maritime, has also been expressed in E. coli and crystallized (Diao et al., Acta Crystallogr. D. Biol. Crystallogr. 59:1100-1102 (2003); Diao and Hasson, J. Bacteriol. 191:2521-2529 (2009)). Aspartokinase catalyzes the ATP-dependent phosphorylation of aspartate and participates in the synthesis of several amino acids. The aspartokinase III enzyme in E. coli, encoded by lysC, has a broad substrate range, and the catalytic residues involved in substrate specificity have been elucidated (Keng and Viola, Arch. Biochem. Biophys. 335:73-81 (1996)). Two additional kinases in E. coli are also good candidates: acetate kinase and gamma-glutamyl kinase. The E. coli acetate kinase, encoded by ackA (Skarstedt and Silverstein, J. Biol. Chem. 251:6775-6783 (1976)), phosphorylates propionate in addition to acetate (Hesslinger et al., Mol. Microbiol. 27:477-492 (1998)). The E. coli gamma-glutamyl kinase, encoded by proB (Smith et al., J. Bacteriol. 157:545-551 (1984)), phosphorylates the gamma carbonic acid group of glutamate.

Gene
Accession No.
GI No.
Organism

buk1
NP_349675
15896326

Clostridium acetobutylicum

buk2
Q97II1
20137415

Clostridium acetobutylicum

buk2
Q9X278.1
6685256

Thermotoga maritima

lysC
NP_418448.1
16131850

Escherichia coli

ackA
NP_416799.1
16130231

Escherichia coli

proB
NP_414777.1
16128228

Escherichia coli

buk
YP_001307350.1
150015096

Clostridium beijerinckii

buk2
YP_001311072.1
150018818

Clostridium beijerinckii

E) Phosphotrans-4-Hydroxybutyrylase (Designated as EB6).

EB6 catalyzes the transfer of the 4-hydroxybutyryl group from phosphate to CoA. Acyltransferases suitable for catalyzing this reaction include phosphotransacetylase and phosphotransbutyrylase. The pta gene from E. coli encodes an enzyme that can convert acetyl-phosphate into acetyl-CoA (Suzuki, Biochim. Biophys. Acta 191:559-569 (1969)). This enzyme can also utilize propionyl-CoA instead of acetyl-CoA (Hesslinger et al., Mol. Microbiol. 27:477-492 (1998)). Similarly, the ptb gene from C. acetobutylicum encodes an enzyme that can convert butyryl-CoA into butyryl-phosphate (Walter et al., Gene 134:107-111 (1993)); Huang et al., J Mol. Microbiol. Biotechno.l 2:33-38 (2000). Additional ptb genes can be found in Clostridial organisms, butyrate-producing bacterium L2-50 (Louis et al., J. Bacteriol. 186:2099-2106 (2004)) and Bacillus megaterium (Vazquez et al., Curr. Microbiol. 42:345-349 (2001)).

Gene
Accession No.
GI No.
Organism

pta
NP_416800.1
16130232

Escherichia coli

ptb
NP_349676
15896327

Clostridium acetobutylicum

ptb
YP_001307349.1
150015095

Clostridium beijerinckii

ptb
AAR19757.1
38425288
butyrate-producing bacterium L2-50

ptb
CAC07932.1
10046659

Bacillus megaterium

F) 4-Hydroxybutyryl-CoA Reductase (Aldehyde Forming).

Enzymes with this activity are described above.

G) 1,4-Butanediol Dehydrogenase (Designated as EB8).

EB8 catalyzes the reduction of 4-hydroxybutyraldehyde to 1,4-butanediol. Exemplary genes encoding this activity include alrA of Acinetobacter sp. strain M-1 (Tani et al., Appl. Environ. Microbiol. 66:5231-5235 (2000)), yqhD and fucO from E. coli (Sulzenbacher et al., J Mol Biol 342:489-502 (2004)) and bdh I and bdh II from C. acetobutylicum (Walter et al, J. Bacteriol 174:7149-7158 (1992)). Additional EB8 enzymes are encoded by bdh in C. saccharoperbutylacetonicum and Cbei_1722, Cbei_2181 and Cbei_2421 in C. beijerinckii. These and other enzymes with 1,4-butanediol activity are listed in the table below.

GI

Protein
GenBank ID
Number
Organism

alrA
BAB12273.1
9967138

Acinetobacter sp. strain M-1

ADH2
NP_014032.1
6323961

Saccharomyces cerevisiae

fucO
NP_417279.1
16130706

Escherichia coli

yqhD
NP_417484.1
16130909

Escherichia coli

bdh I
NP_349892.1
15896543

Clostridium acetobutylicum

bdh II
NP_349891.1
15896542

Clostridium acetobutylicum

bdh
BAF45463.1
124221917

Clostridium

saccharoperbutylacetonicum

Cbei_1722
YP_001308850
150016596

Clostridium beijerinckii

Cbei_2181
YP_001309304
150017050

Clostridium beijerinckii

Cbei_2421
YP_001309535
150017281

Clostridium beijerinckii

14bdh
AAC76047.1
1789386

Escherichia coli K-12

MG1655

14bdh
YP_001309304.1
150017050

Clostridium beijerinckii

NCIMB 8052

14bdh
P13604.1
113352

Clostridium saccharobutylicum

14bdh
ZP_03760651.1
225405462

Clostridium asparagiforme

DSM 15981

14bdh
ZP_02083621.1
160936248

Clostridium bolteae

ATCC BAA-613

14bdh
YP_003845251.1
302876618

Clostridium cellulovorans

743B

14bdh
ZP_03294286.1
210624270

Clostridium hiranonis

DSM 13275

14bdh
ZP_03705769.1
225016577

Clostridium methylpentosum

DSM 5476

14bdh
YP_003179160.1
257783943

Atopobium parvulum

DSM 20469

14bdh
YP_002893476.1
237809036

Tolumonas auensis

DSM 9187

14bdh
ZP_05394983.1
255528157

Clostridium

carboxidivorans P7

H) Succinate Reductase.

Direct reduction of succinate to succinate semialdehyde is catalyzed by a carboxylic acid reductase. Exemplary enzymes for catalyzing this transformation are also those described below and herein for K) 4-Hydroxybutyrate reductase.

I) Succinyl-CoA Reductase (Alcohol Forming) (Designated as EB10).

EB10 enzymes are bifunctional oxidoreductases that convert succinyl-CoA to 4-HB. Enzyme candidates described below and herein for M) 4-hydroxybutyryl-CoA reductase (alcohol forming) are also suitable for catalyzing the reduction of succinyl-CoA.

J) 4-Hydroxybutyryl-CoA Transferase or 4-Hydroxybutyryl-CoA Synthetase (Designated as EB11).

Conversion of 4-HB to 4-hydroxybutyryl-CoA is catalyzed by a CoA transferase or synthetase. EB11 enzymes include the gene products of cat1, cat2, and cat3 of Clostridium kluyveri (Seedorf et al., Proc. Natl. Acad. Sci U.S.A 105:2128-2133 (2008); Sohling et al., J Bacteriol. 178:871-880 (1996)). Similar CoA transferase activities are also present in Trichomonas vaginalis, Trypanosoma brucei, Clostridium aminobutyricum and Porphyromonas gingivalis (Riviere et al., J. Biol. Chem. 279:45337-45346 (2004); van Grinsven et al., J. Biol. Chem. 283:1411-1418 (2008)).

Protein
GenBank ID
GI Number
Organism

cat1
P38946.1
729048

Clostridium kluyveri

cat2
P38942.2
172046066

Clostridium kluyveri

cat3
EDK35586.1
146349050

Clostridium kluyveri

TVAG_395550
XP_001330176
123975034

Trichomonas vaginalis G3

Tb11.02.0290
XP_828352
71754875

Trypanosoma brucei

cat2
CAB60036.1
6249316

Clostridium

aminobutyricum

cat2
NP_906037.1
34541558

Porphyromonas gingivalis

W83

4HB-CoA synthetase catalyzes the ATP-dependent conversion of 4-HB to 4-hydroxybutyryl-CoA. AMP-forming 4-HB-CoA synthetase enzymes are found in organisms that assimilate carbon via the dicarboxylate/hydroxybutyrate cycle or the 3-hydroxypropionate/4-HB cycle. Enzymes with this activity have been characterized in Thermoproteus neutrophilus and Metallosphaera sedula (Ramos-Vera et al, J Bacteriol 192:5329-40 (2010); Berg et al, Science 318:1782-6 (2007)). Others can be inferred by sequence homology. ADP forming CoA synthetases, such EB2A, are also suitable candidates.

Protein
GenBank ID
GI Number
Organism

Tneu_0420
ACB39368.1
170934107

Thermoproteus

neutrophilus

Caur_0002
YP_001633649.1
163845605

Chloroflexus aurantiacus

J-10-fl

Cagg_3790
YP_002465062
219850629

Chloroflexus aggregans

DSM 9485

acs
YP_003431745
288817398

Hydrogenobacter

thermophilus TK-6

Pisl_0250
YP_929773.1
119871766

Pyrobaculum islandicum

DSM 4184

Msed_1422
ABP95580.1
145702438

Metallosphaera sedula

K) 4-HB Reductase.

Reduction of 4-HB to 4-hydroxybutanal is catalyzed by a carboxylic acid reductase (CAR) such as the Car enzyme found in Nocardia iowensis. This enzyme and other carboxylic acid reductases are described above (see EC 1.2.1.e).

L) 4-Hydroxybutyryl-Phosphate Reductase (Designated as EB14).

EB14 catalyzes the reduction of 4-hydroxybutyrylphosphate to 4-hydroxybutyraldehyde. An enzyme catalyzing this transformation has not been identified to date. However, similar enzymes include phosphate reductases in the EC class 1.2.1. Exemplary phosphonate reductase enzymes include G3P dehydrogenase (EC 1.2.1.12), aspartate-semialdehyde dehydrogenase (EC 1.2.1.11) acetylglutamylphosphate reductase (EC 1.2.1.38) and glutamate-5-semialdehyde dehydrogenase (EC 1.2.1.-). Aspartate semialdehyde dehydrogenase (ASD, EC 1.2.1.11) catalyzes the NADPH-dependent reduction of 4-aspartyl phosphate to aspartate-4-semialdehyde. ASD participates in amino acid biosynthesis and recently has been studied as an antimicrobial target (Hadfield et al., Biochemistry 40:14475-14483 (2001)). The E. coli ASD structure has been solved (Hadfield et al., J Mol. Biol. 289:991-1002 (1999)) and the enzyme has been shown to accept the alternate substrate beta-3-methylaspartyl phosphate (Shames et al., J Biol. Chem. 259:15331-15339 (1984)). The Haemophilus influenzae enzyme has been the subject of enzyme engineering studies to alter substrate binding affinities at the active site (Blanco et al., Acta Crystallogr. D. Biol. Crystallogr. 60:1388-1395 (2004); Blanco et al., Acta Crystallogr. D. Biol. Crystallogr. 60:1808-1815 (2004)). Other ASD candidates are found in Mycobacterium tuberculosis (Shafiani et al., J Appl Microbiol 98:832-838 (2005)), Methanococcus jannaschii (Faehnle et al., J Mol. Biol. 353:1055-1068 (2005)), and the infectious microorganisms Vibrio cholera and Heliobacter pylori (Moore et al., Protein Expr. Purif. 25:189-194 (2002)). A related enzyme candidate is acetylglutamylphosphate reductase (EC 1.2.1.38), an enzyme that naturally reduces acetylglutamylphosphate to acetylglutamate-5-semialdehyde, found in S. cerevisiae (Pauwels et al., Eur. J Biochem. 270:1014-1024 (2003)), B. subtilis (O'Reilly et al., Microbiology 140 (Pt 5):1023-1025 (1994)), E. coli (Parsot et al., Gene. 68:275-283 (1988)), and other organisms. Additional phosphate reductase enzymes of E. coli include glyceraldehyde 3-phosphate dehydrogenase (gapA (Branlant et al., Eur. J. Biochem. 150:61-66 (1985))) and glutamate-5-semialdehyde dehydrogenase (proA (Smith et al., J. Bacteriol. 157:545-551 (1984))). Genes encoding glutamate-5-semialdehyde dehydrogenase enzymes from Salmonella typhimurium (Mahan et al., J Bacteriol. 156:1249-1262 (1983)) and Campylobacter jejuni (Louie et al., Mol. Gen. Genet. 240:29-35 (1993)) were cloned and expressed in E. coli.

Protein
GenBank ID
GI Number
Organism

asd
NP_417891.1
16131307

Escherichia coli

asd
YP_248335.1
68249223

Haemophilus influenzae

asd
AAB49996
1899206

Mycobacterium

tuberculosis

VC2036
NP_231670
15642038

Vibrio cholera

asd
YP_002301787.1
210135348

Heliobacter pylori

ARG5,6
NP_010992.1
6320913

Saccharomyces cerevisiae

argC
NP_389001.1
16078184

Bacillus subtilis

argC
NP_418393.1
16131796

Escherichia coli

gapA
P0A9B2.2
71159358

Escherichia coli

proA
NP_414778.1
16128229

Escherichia coli

proA
NP_459319.1
16763704

Salmonella typhimurium

proA
P53000.2
9087222

Campylobacter jejuni

M) 4-Hydroxybutyryl-CoA Reductase (Alcohol Forming) (Designated as EB15).

EB15 enzymes are bifunctional oxidoreductases that convert an 4-hydroxybutyryl-CoA to 1,4-butanediol. Enzymes with this activity include adhE from E. coli, adhE2 from C. acetobutylicum (Fontaine et al., J. Bacteriol. 184:821-830 (2002)) and the C. acetobutylicum enzymes encoded by bdh I and bdh II (Walter, et al., J. Bacteriol. 174:7149-7158 (1992)). In addition to reducing acetyl-CoA to ethanol, the enzyme encoded by adhE in Leuconostoc mesenteroides has been shown to oxide the branched chain compound isobutyraldehyde to isobutyryl-CoA (Kazahaya et al., J. Gen. Appl. Microbiol. 18:43-55 (1972); Koo et al., Biotechnol Lett, 27:505-510 (2005)).

Protein
GenBank ID
GI Number
Organism

adhE
NP_415757.1
16129202

Escherichia coli

adhE2
AAK09379.1
12958626

Clostridium

acetobutylicum

bdh I
NP_349892.1
15896543

Clostridium

acetobutylicum

bdh II
NP_349891.1
15896542

Clostridium

acetobutylicum

adhE
AAV66076.1
55818563

Leuconostoc

mesenteroides

adhE
NP_781989.1
28211045

Clostridium tetani

adhE
NP_563447.1
18311513

Clostridium perfringens

adhE
YP_001089483.1
126700586

Clostridium difficile

Example XII
Adipate, 6-Aminocaproate, Caprolactam and Hexamethylenediamine Synthesis Enzymes

This Example provides genes that can be used for conversion of succinyl-CoA and acetyl-CoA to adipate, 6-aminocaproate, caprolactam and hexamethylenediamine as depicted in the pathways of FIG. 8.

FIG. 8. depicts enzymes: A) 3-oxoadipyl-CoA thiolase, B) 3-oxoadipyl-CoA reductase, C) 3-hydroxyadipyl-CoA dehydratase, D) 5-carboxy-2-pentenoyl-CoA reductase, E) adipyl-CoA reductase (aldehyde forming), F) 6-aminocaproate transaminase, or 6-aminocaproate dehydrogenase, G) 6-aminocaproyl-CoA/acyl-CoA transferase, or 6-aminocaproyl-CoA synthase, H) amidohydrolase, I) spontaneous cyclization, J) 6-aminocaproyl-CoA reductase (aldehyde forming), K) HMDA transaminase or HMDA dehydrogenase, L) Adipyl-CoA hydrolase, adipyl-CoA ligase, adipyl-CoA transferase, or phosphotransadipylase/adipate kinase. Transformations depicted in FIG. 8 fall into at least 10 general categories of transformations shown in the Table below. The first three digits of each label correspond to the first three Enzyme Commission number digits which denote the general type of transformation independent of substrate specificity. Below is described a number of biochemically characterized candidate genes in each category. Specifically listed are exemplary genes that can be applied to catalyze the appropriate transformations in FIG. 8 when cloned and expressed.

Step
Label
Function

FIG. 8, step B
1.1.1.a
Oxidoreductase (ketone

to hydroxyl or aldehyde

to alcohol)

FIG. 8, steps E and J
1.2.1.b
Oxidoreductase (acyl-CoA

to aldehyde)

FIG. 8, step D
1.3.1.a
Oxidoreductase operating on

CH-CH donors

FIG. 8, steps F and K
1.4.1.a
Oxidoreductase operating

on amino acids

FIG. 8, step A
2.3.1.b
Acyltransferase

FIG. 8, steps F and K
2.6.1.a
Aminotransferase

FIG. 8, steps G and L
2.8.3.a
Coenzyme-A transferase

FIG. 8, steps G and L
6.2.1.a
Acid-thiol ligase

FIG. 8, Step H
6.3.1.a/6.3.2.a
Amide synthases/peptide

synthases

FIG. 8, step I
No enzyme
Spontaneous cyclization

required

FIG. 8, Step A—3-Oxoadipyl-CoA Thiolase.
EC 2.3.1.b Acyl Transferase.

The first step in the pathway combines acetyl-CoA and succinyl-CoA to form 3-oxoadipyl-CoA. Step A can involve a 3-oxoadipyl-CoA thiolase, or equivalently, succinyl CoA:acetyl CoA acyl transferase (β-ketothiolase). The gene products encoded by pcaF in Pseudomonas strain B13 (Kaschabek et al., J. Bacteriol. 184:207-215 (2002)), phaD in Pseudomonas putida U (Olivera et al., Proc. Natl. Acad. Sci. USA 95:6419-6424 (1998)), paaE in Pseudomonas fluorescens ST (Di Gennaro et al., Arch. Microbiol. 188:117-125 (2007)), and paaJ from E. coli (Nogales et al., Microbiol. 153:357-365 (2007)) catalyze the conversion of 3-oxoadipyl-CoA into succinyl-CoA and acetyl-CoA during the degradation of aromatic compounds such as phenylacetate or styrene. Since beta-ketothiolase enzymes catalyze reversible transformations, these enzymes can be employed for the synthesis of 3-oxoadipyl-CoA. For example, the ketothiolase phaA from R. eutropha combines two molecules of acetyl-CoA to form acetoacetyl-CoA (Sato et al., J Biosci Bioeng 103:38-44 (2007)). Similarly, a β-keto thiolase (bktB) has been reported to catalyze the condensation of acetyl-CoA and propionyl-CoA to form β-ketovaleryl-CoA (Slater et al., J. Bacteriol. 180:1979-1987 (1998)) in R. eutropha. The protein sequences for the above-mentioned gene products are well known in the art and can be accessed in the public databases such as GenBank using the following accession numbers.

Gene name
GI Number
GenBank ID
Organism

paaJ
16129358
NP_415915.1

Escherichia coli

pcaF
17736947
AAL02407

Pseudomonas

knackmussii (B13)

phaD
3253200
AAC24332.1

Pseudomonas putida

paaE
106636097
ABF82237.1

Pseudomonas fluorescens

These exemplary sequences can be used to identify homologue proteins in GenBank or other databases through sequence similarity searches (for example, BLASTp). The resulting homologue proteins and their corresponding gene sequences provide additional exogenous DNA sequences for transformation into E. coli or other suitable host microorganisms to generate production hosts. For example, orthologs of paaJ from Escherichia coli K12 can be found using the following GenBank accession numbers:

GI Number
GenBank ID
Organism

152970031
YP_001335140.1

Klebsiella pneumoniae

157371321
YP_001479310.1

Serratia

3253200
AAC24332.1

Pseudomonas putida

Example orthologs of pcaF from Pseudomonas knackmussii can be found using the following GenBank accession numbers:

GI Number
GenBank ID
Organism

4530443
AAD22035.1

Streptomyces sp. 2065

24982839
AAN67000.1

Pseudomonas putida

115589162
ABJ15177.1

Pseudomonas

Additional native candidate genes for the ketothiolase step include atoB, which can catalyze the reversible condensation of 2 acetyl-CoA molecules (Sato et al., J. Biosci. Bioengineer. 103:38-44 (2007)), and its homolog yqeF. Non-native gene candidates include phaA (Sato et al., supra, 2007) and bktB (Slater et al., J. Bacteriol. 180:1979-1987 (1998)) from R. eutropha, and the two ketothiolases, thiA and thiB, from Clostridium acetobutylicum (Winzer et al., J. Mol. Microbiol. Biotechnol. 2:531-541 (2000)). The protein sequences for each of these exemplary gene products can be found using the following GenBank accession numbers:

Gene Name
GenBank ID
Organism

atoB
NP_416728.1

Escherichia coli

yqeF
NP_417321.2

Escherichia coli

phaA
YP_725941

Ralstonia eutropha

bktB
AAC38322.1

Ralstonia eutropha

thiA
NP_349476.1

Clostridium acetobutylicum

thiB
NP_149242.1

Clostridium acetobutylicum

2-Amino-4-oxopentanoate (AKP) thiolase or AKP thiolase (AKPT) enzymes present additional candidates for performing step A. AKPT is a pyridoxal phosphate-dependent enzyme participating in ornithine degradation in Clostridium sticklandii (Jeng et al., Biochemistry 13:2898-2903 (1974); Kenklies et al., Microbiology 145:819-826 (1999)). A gene cluster encoding the alpha and beta subunits of AKPT (or-2 (ortA) and or-3 (ortB)) was recently identified and the biochemical properties of the enzyme were characterized (Fonknechten et al., J. Bacteriol. In Press (2009)). The enzyme is capable of operating in both directions and naturally reacts with the D-isomer of alanine. AKPT from Clostridium sticklandii has been characterized but its protein sequence has not yet been published. Enzymes with high sequence homology are found in Clostridium difficile, Alkaliphilus metalliredigenes QYF, Thermoanaerobacter sp. X514, and Thermoanaerobacter tengcongensis MB4 (Fonknechten et al., supra).

Gene name
GI Number
GenBank ID
Organism

ortA (α)
126698017
YP_001086914.1

Clostridium difficile 630

ortB (β)
126698018
YP_001086915.1

Clostridium difficile 630

Amet_2368 (α)
150390132
YP_001320181.1

Alkaliphilus metalliredigenes QYF

Amet_2369 (β)
150390133
YP_001320182.1

Alkaliphilus metalliredigenes QYF

Teth514_1478 (α)
167040116
YP_001663101.1

Thermoanaerobacter sp. X514

Teth514_1479 (β)
167040117
YP_001663102.1

Thermoanaerobacter sp. X514

TTE1235 (α)
20807687
NP_622858.1

Thermoanaerobacter tengcongensis

MB4

thrC (β)
20807688
NP_622859.1

Thermoanaerobacter tengcongensis

MB4

Step B—3-Oxoadipyl-CoA Reductase.

EC 1.1.1.a Oxidoreductases.

Certain transformations depicted in FIG. 8 involve oxidoreductases that convert a ketone functionality to a hydroxyl group. For example, FIG. 8, step B involves the reduction of a 3-oxoacyl-CoA to a 3-hydroxyacyl-CoA.

Exemplary enzymes that can convert 3-oxoacyl-CoA molecules, such as 3-oxoadipyl-CoA, into 3-hydroxyacyl-CoA molecules, such as 3-hydroxyadipyl-CoA, include enzymes whose natural physiological roles are in fatty acid beta-oxidation or phenylacetate catabolism. For example, subunits of two fatty acid oxidation complexes in E. coli, encoded by fadB and fadJ, function as 3-hydroxyacyl-CoA dehydrogenases (Binstock et al., Methods Enzymol. 71:403-411 (1981)). Furthermore, the gene products encoded by phaC in Pseudomonas putida U (Olivera et al., Proc. Natl. Acad. Sci. USA 95:6419-6424 (1998)) and paaC in Pseudomonas fluorescens ST (Di Gennaro et al., Arch. Microbiol. 188:117-125 (2007)) catalyze the reverse reaction of step B in FIG. 8, that is, the oxidation of 3-hydroxyadipyl-CoA to form 3-oxoadipyl-CoA, during the catabolism of phenylacetate or styrene. Note that the reactions catalyzed by such enzymes are reversible. A similar transformation is also carried out by the gene product of hbd in Clostridium acetobutylicum (Atsumi et al., Metab. Eng. (epub Sep. 14, 2007); Boynton et al., J. Bacteriol. 178:3015-3024 (1996)). This enzyme converts acetoacetyl-CoA to 3-hydroxybutyryl-CoA. In addition, given the proximity in E. coli of paaH to other genes in the phenylacetate degradation operon (Nogales et al., Microbiology 153:357-365 (2007)) and the fact that paaH mutants cannot grow on phenylacetate (Ismail et al., Eur. J Biochem. 270:3047-3054 (2003)), it is expected that the E. coli paaH gene encodes a 3-hydroxyacyl-CoA dehydrogenase.

Gene name
GI Number
GenBank ID
Organism

fadB
119811
P21177.2

Escherichia coli

fadJ
3334437
P77399.1

Escherichia coli

paaH
16129356
NP_415913.1

Escherichia coli

phaC
26990000
NP_745425.1

Pseudomonas putida

paaC
106636095
ABF82235.1

Pseudomonas fluorescens

Additional exemplary oxidoreductases capable of converting 3-oxoacyl-CoA molecules to their corresponding 3-hydroxyacyl-CoA molecules include 3-hydroxybutyryl-CoA dehydrogenases. The enzyme from Clostridium acetobutylicum, encoded by hbd, has been cloned and functionally expressed in E. coli (Youngleson et al., J. Bacteriol. 171:6800-6807 (1989)). Additional gene candidates include Hbd1 (C-terminal domain) and Hbd2 (N-terminal domain) in Clostridium kluyveri (Hillmer et al., FEBS Lett. 21:351-354 (1972)) and HSD17B10 in Bos taurus (Wakil et al., J. Biol. Chem. 207:631-638 (1954)). Yet other gene candidates demonstrated to reduce acetoacetyl-CoA to 3-hydroxybutyryl-CoA are phbB from Zoogloea ramigera (Ploux et al., Eur. J. Biochem. 174:177-182 (1988)) and phaB from Rhodobacter sphaeroides (Alber et al., Mol. Microbiol 61:297-309 (2006)). The former gene candidate is NADPH-dependent, its nucleotide sequence has been determined (Peoples et al., Mol. Microbiol 3:349-357 (1989)) and the gene has been expressed in E. coli. Substrate specificity studies on the gene led to the conclusion that it could accept 3-oxopropionyl-CoA as a substrate besides acetoacetyl-CoA (Ploux et al., supra).

Gene name
GI Number
GenBank ID
Organism

hbd
18266893
P52041.2

Clostridium

acetobutylicum

Hbd2
146348271
EDK34807.1

Clostridium kluyveri

Hbd1
146345976
EDK32512.1

Clostridium kluyveri

HSD17B10
3183024
O02691.3

Bos taurus

phbB
130017
P23238.1

Zoogloea ramigera

phaB
146278501
YP_001168660.1

Rhodobacter sphaeroides

A number of similar enzymes have been found in other species of Clostridia and in Metallosphaera sedula (Berg et al., Science 318:1782-1786 (2007)).

Gene name
GI Number
GenBank ID
Organism

hbd
15895965
NP_349314.1

Clostridium

acetobutylicum

hbd
20162442
AAM14586.1

Clostridium beijerinckii

Msed_1423
146304189
YP_001191505

Metallosphaera sedula

Msed_0399
146303184
YP_001190500

Metallosphaera sedula

Msed_0389
146303174
YP_001190490

Metallosphaera sedula

Msed_1993
146304741
YP_001192057

Metallosphaera sedula

Step C—3-Hydroxyadipyl-CoA Dehydratase.

Step C can involve a 3-hydroxyadipyl-CoA dehydratase. The gene product of crt from C. acetobutylicum catalyzes the dehydration of 3-hydroxybutyryl-CoA to crotonyl-CoA (Atsumi et al., Metab. Eng. (epub Sep. 14, 2007); Boynton et al., J. Bacteriol. 178:3015-3024 (1996)). Homologs of this gene are strong candidates for carrying out the third step (step C) in the synthesis pathways exemplified in FIG. 8. In addition, genes known to catalyze the hydroxylation of double bonds in enoyl-CoA compounds represent additional candidates given the reversibility of such enzymatic transformations. For example, the enoyl-CoA hydratases, phaA and phaB, of P. putida are believed to carry out the hydroxylation of double bonds during phenylacetate catabolism (Olivera et al., Proc. Natl. Acad. Sci. USA 95:6419-6424 (1998)) and thus represent additional candidates for incorporation into E. coli. The deletion of these genes precludes phenylacetate degradation in P. putida. The paaA and paaB from P. fluorescens catalyze analogous transformations (Olivera et al., Proc. Natl. Acad. Sci. USA 95:6419-6424 (1998)). Lastly, a number of Escherichia coli genes have been shown to demonstrate enoyl-CoA hydratase functionality including maoC (Park and Lee, J. Bacteriol. 185:5391-5397 (2003)), paaF (Ismail et al., Eur. J. Biochem. 270:3047-3054 (2003); Park and Lee, Biotechnol. Bioeng. 86:681-686 (2004); Park and Lee, Appl. Biochem. Biotechnol. 113-116:335-346 (2004)), and paaG (Ismail et al., supra, 2003; Park and Lee, supra, 2003; Park and Lee, supra, 2004). The protein sequences for each of these exemplary gene products can be found using the following GenBank accession numbers:

Gene Name
GenBank ID
Organism

maoC
NP_415905.1

Escherichia coli

paaF
NP_415911.1

Escherichia coli

paaG
NP_415912.1

Escherichia coli

crt
NP_349318.1

Clostridium acetobutylicum

paaA
NP_745427.1

Pseudomonas putida

paaB
NP_745426.1

Pseudomonas putida

phaA
ABF82233.1

Pseudomonas fluorescens

phaB
ABF82234.1

Pseudomonas fluorescens

Alternatively, beta-oxidation genes are candidates for the first three steps in adipate synthesis. Candidate genes for the proposed adipate synthesis pathway also include the native fatty acid oxidation genes of E. coli and their homologs in other organisms. The E. coli genes fadA and fadB encode a multienzyme complex that exhibits ketoacyl-CoA thiolase, 3-hydroxyacyl-CoA dehydrogenase, and enoyl-CoA hydratase activities (Yang et al., Biochem. 30:6788-6795 (1991); Yang et al., J. Biol. Chem. 265:10424-10429 (1990); Yang et al., J. Biol. Chem. 266:16255 (1991); Nakahigashi and Inokuchi, Nucl. Acids Res. 18: 4937 (1990)). These activities are mechanistically similar to the first three transformations shown in FIG. 8. The fadI and fadJ genes encode similar functions and are naturally expressed only anaerobically (Campbell et al., Mol. Microbiol. 47:793-805 (2003)). These gene products naturally operate to degrade short, medium, and long chain fatty-acyl-CoA compounds to acetyl-CoA, rather than to convert succinyl-CoA and acetyl-CoA into 5-carboxy-2-pentenoyl-CoA as proposed in FIG. 8. However, it is well known that the ketoacyl-CoA thiolase, 3-hydroxyacyl-CoA dehydrogenase, and enoyl-CoA hydratase enzymes catalyze reversible transformations. Furthermore, directed evolution and related approaches can be applied to tailor the substrate specificities of the native beta-oxidation machinery of E. coli. Thus these enzymes or homologues thereof can be applied for adipate production. If the native genes operate to degrade adipate or its precursors in vivo, the appropriate genetic modifications are made to attenuate or eliminate these functions. However, it may not be necessary since a method for producing poly[(R)-3-hydroxybutyrate] in E. coli that involves activating fadB, by knocking out a negative regulator, fadR, and co-expressing a non-native ketothiolase, phaA from Ralstonia eutropha, has been described (Sato et al., J. Biosci. Bioeng. 103:38-44 (2007)). This work clearly demonstrated that a—oxidation enzyme, in particular the gene product of fadB which encodes both 3-hydroxyacyl-CoA dehydrogenase and enoyl-CoA hydratase activities, can function as part of a pathway to produce longer chain molecules from acetyl-CoA precursors. The protein sequences for each of these exemplary gene products can be found using the following GenBank accession numbers:

Gene Name
GenBank ID
Organism

fadA
YP_026272.1

Escherichia coli

fadB
NP_418288.1

Escherichia coli

fadI
NP_416844.1

Escherichia coli

fadJ
NP_416843.1

Escherichia coli

fadR
NP_415705.1

Escherichia coli

Step D—5-Carboxy-2-Pentenoyl-CoA Reductase. EC 1.3.1.a Oxidoreductase Operating on CH—CH Donors.

Step D involves the conversion of 5-carboxy-2-pentenoyl-CoA to adipyl-CoA by 5-carboxy-2-pentenoyl-CoA reductase. Enoyl-CoA reductase enzymes are suitable enzymes for this transformation.

Whereas the ketothiolase, dehydrogenase, and enoyl-CoA hydratase steps are generally reversible, the enoyl-CoA reductase step is almost always oxidative and irreversible under physiological conditions (Hoffmeister et al., J. Biol. Chem. 280:4329-4338 (2005)). FadE catalyzes this likely irreversible transformation in E. coli (Campbell and Cronan, J. Bacteriol. 184:3759-3764 (2002)). The pathway can involve an enzyme that reduces a 2-enoyl-CoA intermediate, not one such as FadE that will only oxidize an acyl-CoA to a 2-enoyl-CoA compound. Furthermore, although it has been suggested that E. coli naturally possesses enzymes for enoyl-CoA reduction (Mizugaki et al., J. Biochem. 92:1649-1654 (1982); Nishimaki et al., J. Biochem. 95:1315-1321 (1984)), no E. coli gene possessing this function has been biochemically characterized.

One exemplary enoyl-CoA reductase is the gene product of bcd from C. acetobutylicum (Boynton et al., J Bacteriol. 178:3015-3024 (1996); Atsumi et al., Metab. Eng. 2008 10(6):305-311 (2008) (Epub Sep. 14, 2007), which naturally catalyzes the reduction of crotonyl-CoA to butyryl-CoA. Activity of this enzyme can be enhanced by expressing bcd in conjunction with expression of the C. acetobutylicum etfAB genes, which encode an electron transfer flavoprotein. An additional candidate for the enoyl-CoA reductase step is the mitochondrial enoyl-CoA reductase from E. gracilis (Hoffmeister et al., J. Biol. Chem. 280:4329-4338 (2005)). A construct derived from this sequence following the removal of its mitochondrial targeting leader sequence was cloned in E. coli resulting in an active enzyme (Hoffmeister et al., supra). This approach is well known to those skilled in the art of expressing eukaryotic genes, particularly those with leader sequences that may target the gene product to a specific intracellular compartment, in prokaryotic organisms. A close homolog of this gene, TDE0597, from the prokaryote Treponema denticola represents a third enoyl-CoA reductase which has been cloned and expressed in E. coli (Tucci et al., FEBS Letters 581:1561-1566 (2007)).

Gene

name
GI Number
GenBank ID
Organism

bcd
15895968
NP_349317.1

Clostridium acetobutylicum

etfA
15895966
NP_349315.1

Clostridium acetobutylicum

etfB
15895967
NP_349316.1

Clostridium acetobutylicum

TER
62287512
Q5EU90.1

Euglena gracilis

TDE0597
42526113
NP_971211.1

Treponema denticola

Step E—Adipyl-CoA Reductase (Aldehyde Forming). EC 1.2.1.b Oxidoreductase (Acyl-CoA to Aldehyde).

The transformation of adipyl-CoA to adipate semialdehyde in step E can involve an acyl-CoA dehydrogenases capable of reducing an acyl-CoA to its corresponding aldehyde. An EC 1.2.1.b oxidoreductase (acyl-CoA to aldehyde) provides suitable enzyme activity. Exemplary enzymes in this class are described herein and above (for example see description for 3-Hydroxybutyryl-CoA Reductase (aldehyde forming)).

Step F—6-Aminocaproate Transaminase or 6-Aminocaproate Dehydrogenase. EC 1.4.1.a Oxidoreductase Operating on Amino Acids.

Step F depicts a reductive amination involving the conversion of adipate semialdehyde to 6-aminocaproate.

Most oxidoreductases operating on amino acids catalyze the oxidative deamination of alpha-amino acids with NAD+ or NADP+ as acceptor, though the reactions are typically reversible. Exemplary oxidoreductases operating on amino acids include glutamate dehydrogenase (deaminating), encoded by gdhA, leucine dehydrogenase (deaminating), encoded by ldh, and aspartate dehydrogenase (deaminating), encoded by nadX. The gdhA gene product from Escherichia coli (McPherson et al., Nucleic. Acids Res. 11:5257-5266 (1983); Korber et al., J. Mol. Biol. 234:1270-1273 (1993)), gdh from Thermotoga maritima (Kort et al., Extremophiles 1:52-60 (1997); Lebbink et al., J. Mol. Biol. 280:287-296 (1998); Lebbink et al., J. Mol. Biol. 289:357-369 (1999)), and gdhA1 from Halobacterium salinarum (Ingoldsby et al., Gene. 349:237-244 (2005)) catalyze the reversible interconversion of glutamate to 2-oxoglutarate and ammonia, while favoring NADP(H), NAD(H), or both, respectively. The ldh gene of Bacillus cereus encodes the LeuDH protein that has a wide of range of substrates including leucine, isoleucine, valine, and 2-aminobutanoate (Stoyan et al., J. Biotechnol 54:77-80 (1997); Ansorge et al., Biotechnol Bioeng. 68:557-562 (2000)). The nadX gene from Thermotoga maritime encoding for the aspartate dehydrogenase is involved in the biosynthesis of NAD (Yang et al., J. Biol. Chem. 278:8804-8808 (2003)).

Gene name
GI Number
GenBank ID
Organism

gdhA
118547
P00370

Escherichia coli

gdh
6226595
P96110.4

Thermotoga maritima

gdhA1
15789827
NP_279651.1

Halobacterium salinarum

ldh
61222614
P0A393

Bacillus cereus

nadX
15644391
NP_229443.1

Thermotoga maritima

The lysine 6-dehydrogenase (deaminating), encoded by the lysDH genes, catalyze the oxidative deamination of the epsilon-amino group of L-lysine to form 2-aminoadipate-6-semialdehyde, which in turn nonenzymatically cyclizes to form Δ¹-piperideine-6-carboxylate (Misono et al., J. Bacteriol. 150:398-401 (1982)). Exemplary enzymes can be found in Geobacillus stearothermophilus (Heydari et al., Appl Environ. Microbiol 70:937-942 (2004)), Agrobacterium tumefaciens (Hashimoto et al., J Biochem 106:76-80 (1989); Misono et al., supra), and Achromobacter denitrificans (Ruldeekulthamrong et al., BMB. Rep. 41:790-795 (2008)). Such enzymes are particularly good candidates for converting adipate semialdehyde to 6-aminocaproate given the structural similarity between adipate semialdehyde and 2-aminoadipate-6-semialdehyde.

Gene name
GI Number
GenBank ID
Organism

lysDH
13429872
BAB39707

Geobacillus

stearothermophilus

lysDH
15888285
NP_353966

Agrobacterium tumefaciens

lysDH
74026644
AAZ94428

Achromobacter denitrificans

EC 2.6.1.a Aminotransferase.

Step F of FIG. 8 can also, in certain embodiments, involve the transamination of a 6-aldehyde to an amine. This transformation can be catalyzed by gamma-aminobutyrate transaminase (GABA transaminase). One E. coli GABA transaminase is encoded by gabT and transfers an amino group from glutamate to the terminal aldehyde of succinyl semialdehyde (Bartsch et al., J. Bacteriol. 172:7035-7042 (1990)). The gene product of puuE catalyzes another 4-aminobutyrate transaminase in E. coli (Kurihara et al., J. Biol. Chem. 280:4602-4608 (2005)). GABA transaminases in Mus musculus, Pseudomonas fluorescens, and Sus scrofa have been shown to react with 6-aminocaproic acid (Cooper, Methods Enzymol. 113:80-82 (1985); Scott et al., J. Biol. Chem. 234:932-936 (1959)).

Gene name
GI Number
GenBank ID
Organism

gabT
16130576
NP_417148.1

Escherichia coli

puuE
16129263
NP_415818.1

Escherichia coli

abat
37202121
NP_766549.2

Mus musculus

gabT
70733692
YP_257332.1

Pseudomonas fluorescens

abat
47523600
NP_999428.1

Sus scrofa

Additional enzyme candidates include putrescine aminotransferases or other diamine aminotransferases. Such enzymes are particularly well suited for carrying out the conversion of 6-aminocaproate semialdehyde to hexamethylenediamine. The E. coli putrescine aminotransferase is encoded by the ygjG gene and the purified enzyme also was able to transaminate cadaverine and spermidine (Samsonova et al., BMC Microbiol 3:2 (2003)). In addition, activity of this enzyme on 1,7-diaminoheptane and with amino acceptors other than 2-oxoglutarate (e.g., pyruvate, 2-oxobutanoate) has been reported (Samsonova et al., supra; Kim, K. H., J Biol Chem 239:783-786 (1964)). A putrescine aminotransferase with higher activity with pyruvate as the amino acceptor than alpha-ketoglutarate is the spuC gene of Pseudomonas aeruginosa (Lu et al., J Bacteriol 184:3765-3773 (2002)).

Gene name
GI Number
GenBank ID
Organism

ygjG
145698310
NP_417544

Escherichia coli

spuC
9946143
AAG03688

Pseudomonas aeruginosa

Yet additional candidate enzymes include beta-alanine/alpha-ketoglutarate aminotransferases which produce malonate semialdehyde from beta-alanine (WO08027742). The gene product of SkPYD4 in Saccharomyces kluyveri was also shown to preferentially use beta-alanine as the amino group donor (Andersen et al., FEBS. J. 274:1804-1817 (2007)). SkUGA1 encodes a homologue of Saccharomyces cerevisiae GABA aminotransferase, UGA1 (Ramos et al., Eur. J. Biochem., 149:401-404 (1985)), whereas SkPYD4 encodes an enzyme involved in both—alanine and GABA transamination (Andersen et al., supra). 3-Amino-2-methylpropionate transaminase catalyzes the transformation from methylmalonate semialdehyde to 3-amino-2-methylpropionate. This enzyme has been characterized in Rattus norvegicus and Sus scrofa and is encoded by Abat (Tamaki et al, Methods Enzymol, 324:376-389 (2000)).

Gene name
GI Number
GenBank ID
Organism

SkyPYD4
98626772
ABF58893.1

Saccharomyces kluyveri

SkUGA1
98626792
ABF58894.1

Saccharomyces kluyveri

UGA1
6321456
NP_011533.1

Saccharomyces cerevisiae

Abat
122065191
P50554.3

Rattus norvegicus

Abat
120968
P80147.2

Sus scrofa

Step G—6-Aminocaproyl-CoA/Acyl-CoA Transferase or 6-Aminocaproyl-CoA Synthase.

2.8.3.a Coenzyme-A Transferase.

CoA transferases catalyze reversible reactions that involve the transfer of a CoA moiety from one molecule to another. For example, step G can be catalyzed by a 6-aminocaproyl-CoA/Acyl CoA transferase. One candidate enzyme for these steps is the two-unit enzyme encoded by pcaI and pcaJ in Pseudomonas, which has been shown to have 3-oxoadipyl-CoA/succinate transferase activity ((Kaschabek and Reineke, J. Bacteriol. 177:320-325 (1995); and Kaschabek. and Reineke, J. Bacteriol. 175:6075-6081 (1993)). Similar enzymes based on homology exist in Acinetobacter sp. ADP1 (Kowalchuk et al., Gene 146:23-30 (1994)) and Streptomyces coelicolor. Additional exemplary succinyl-CoA:3:oxoacid-CoA transferases are present in Helicobacter pylori (Corthesy-Theulaz et al., J. Biol. Chem. 272:25659-25667 (1997)) and Bacillus subtilis (Stols et al., Protein. Expr. Purif 53:396-403 (2007)).

Gene name
GI Number
GenBank ID
Organism

pcaI
24985644
AAN69545.1

Pseudomonas putida

pcaJ
26990657
NP_746082.1

Pseudomonas putida

pcaI
50084858
YP_046368.1

Acinetobacter sp. ADP1

pcaJ
141776
AAC37147.1

Acinetobacter sp. ADP1

pcaI
21224997
NP_630776.1

Streptomyces coelicolor

pcaJ
21224996
NP_630775.1

Streptomyces coelicolor

HPAG1_0676
108563101
YP_627417

Helicobacter pylori

HPAG1_0677
108563102
YP_627418

Helicobacter pylori

ScoA
16080950
NP_391778

Bacillus subtilis

ScoB
16080949
NP_391777

Bacillus subtilis

A 3-oxoacyl-CoA transferase that can utilize acetate as the CoA acceptor is acetoacetyl-CoA transferase, encoded by the E. coli atoA (alpha subunit) and atoD (beta subunit) genes (Vanderwinkel et al., Biochem. Biophys. Res Commun. 33:902-908 (1968); Korolev et al., Acta Crystallogr. D Biol Crystallogr. 58:2116-2121 (2002)). This enzyme has also been shown to transfer the CoA moiety to acetate from a variety of branched and linear acyl-CoA substrates, including isobutyrate (Matthies et al., Appl Environ Microbiol 58:1435-1439 (1992)), valerate (Vanderwinkel et al., supra) and butanoate (Vanderwinkel et al., supra). Similar enzymes exist in Corynebacterium glutamicum ATCC 13032 (Duncan et al., Appl Environ Microbiol 68:5186-5190 (2002)), Clostridium acetobutylicum (Cary et al., Appl Environ Microbiol 56:1576-1583 (1990)), and Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci. Biotechnol Biochem. 71:58-68 (2007)).

Gene
GI

name
Number
GenBank ID
Organism

atoA
2492994
P76459.1

Escherichia coli K12

atoD
2492990
P76458.1

Escherichia coli K12

actA
62391407
YP_226809.1

Corynebacterium glutamicum

ATCC 13032

cg0592
62389399
YP_224801.1

Corynebacterium glutamicum

ATCC 13032

ctfA
15004866
NP_149326.1

Clostridium acetobutylicum

ctfB
15004867
NP_149327.1

Clostridium acetobutylicum

ctfA
31075384
AAP42564.1

Clostridium

saccharoperbutylacetonicum

ctfB
31075385
AAP42565.1

Clostridium

saccharoperbutylacetonicum

The above enzymes may also exhibit the desired activities on 6-aminocaproate and 6-aminocaproyl-CoA, as in step G. Nevertheless, additional exemplary transferase candidates are catalyzed by the gene products of cat1, cat2, and cat3 of Clostridium kluyveri which have been shown to exhibit succinyl-CoA, 4-hydroxybutyryl-CoA, and butyryl-CoA transferase activity, respectively (Seedorf et al., supra; Sohling et al., Eur. J Biochem. 212:121-127 (1993); Sohling et al., J Bacteriol. 178:871-880 (1996)).

Gene name
GI Number
GenBank ID
Organism

cat1
729048
P38946.1

Clostridium kluyveri

cat2
172046066
P38942.2

Clostridium kluyveri

cat3
146349050
EDK35586.1

Clostridium kluyveri

Gene name
GI Number
GenBank ID
Organism

gctA
559392
CAA57199.1

Acidaminococcus fermentans

gctB
559393
CAA57200.1

Acidaminococcus fermentans

EC 6.2.1.a Acid-Thiol Ligase.

Step G can also involve an acid-thiol ligase or synthetase functionality (the terms ligase, synthetase, and synthase are used herein interchangeably and refer to the same enzyme class). Exemplary genes encoding enzymes to carry out these transformations include the sucCD genes of E. coli which naturally form a succinyl-CoA synthetase complex. This enzyme complex naturally catalyzes the formation of succinyl-CoA from succinate with the contaminant consumption of one ATP, a reaction which is reversible in vivo (Buck et al., Biochem. 24:6245-6252 (1985)). Given the structural similarity between succinate and adipate, that is, both are straight chain dicarboxylic acids, it is reasonable to expect some activity of the sucCD enzyme on adipyl-CoA.

GI

Gene name
Number
GenBank ID
Organism

sucC
16128703
NP_415256.1

Escherichia coli

sucD
1786949
AAC73823.1

Escherichia coli

Additional exemplary CoA-ligases include the rat dicarboxylate-CoA ligase for which the sequence is yet uncharacterized (Vamecq et al., Biochemical Journal 230:683-693 (1985)), either of the two characterized phenylacetate-CoA ligases from P. chrysogenum (Lamas-Maceiras et al., Biochem. J. 395:147-155 (2005); Wang et al., Biochem Biophy Res Commun 360(2):453-458 (2007)), the phenylacetate-CoA ligase from Pseudomonas putida (Martinez-Blanco et al., J. Biol. Chem. 265:7084-7090 (1990)), and the 6-carboxyhexanoate-CoA ligase from Bacillus subtilis (Bower et al., J. Bacteriol. 178(14):4122-4130 (1996)). Additional candidate enzymes are acetoacetyl-CoA synthetases from Mus musculus (Hasegawa et al., Biochim Biophys Acta 1779:414-419 (2008)) and Homo sapiens (Ohgami et al., Biochem Pharmacol 65:989-994 (2003)) which naturally catalyze the ATP-dependent conversion of acetoacetate into acetoacetyl-CoA.

Gene name
GI Number
GenBank ID
Organism

phl
77019264
CAJ15517.1

Penicillium chrysogenum

phlB
152002983
ABS19624.1

Penicillium chrysogenum

paaF
22711873
AAC24333.2

Pseudomonas putida

bioW
50812281
NP_390902.2

Bacillus subtilis

AACS
21313520
NP_084486.1

Mus musculus

AACS
31982927
NP_076417.2

Homo sapiens

ADP-forming acetyl-CoA synthetase (ACD, EC 6.2.1.13) is another candidate enzyme that couples the conversion of acyl-CoA esters to their corresponding acids with the concurrent synthesis of ATP. Several enzymes with broad substrate specificities have been described in the literature. ACD I from Archaeoglobus fulgidus, encoded by AF1211, was shown to operate on a variety of linear and branched-chain substrates including acetyl-CoA, propionyl-CoA, butyryl-CoA, acetate, propionate, butyrate, isobutyryate, isovalerate, succinate, fumarate, phenylacetate, indoleacetate (Musfeldt et al., J Bacteriol 184:636-644 (2002)). The enzyme from Haloarcula marismortui (annotated as a succinyl-CoA synthetase) accepts propionate, butyrate, and branched-chain acids (isovalerate and isobutyrate) as substrates, and was shown to operate in the forward and reverse directions (Brasen et al., Arch Microbiol 182:277-287 (2004)). The ACD encoded by PAE3250 from hyperthermophilic crenarchaeon Pyrobaculum aerophilum showed the broadest substrate range of all characterized ACDs, reacting with acetyl-CoA, isobutyryl-CoA (preferred substrate) and phenylacetyl-CoA (Brasen et al., supra). The enzymes from A. fulgidus, H. marismortui and P. aerophilum have all been cloned, functionally expressed, and characterized in E. coli (Musfeldt et al., supra; Brasen et al., supra).

Gene name
GI Number
GenBank ID
Organism

AF1211
11498810
NP_070039.1

Archaeoglobus fulgidus

DSM 4304

Scs
55377722
YP_135572.1

Haloarcula marismortui

ATCC 43049

PAE3250
18313937
NP_560604.1

Pyrobaculum aerophilum

str. IM2

Yet another option is to employ a set of enzymes with net ligase or synthetase activity. For example, phosphotransadipylase and adipate kinase enzymes are catalyzed by the gene products of buk1, buk2, and ptb from C. acetobutylicum (Walter et al., Gene 134:107-111 (1993); Huang et al., J Mol. Microbiol. Biotechnol. 2:33-38 (2000)). The ptb gene encodes an enzyme that can convert butyryl-CoA into butyryl-phosphate, which is then converted to butyrate via either of the buk gene products with the concomitant generation of ATP.

Gene name
GI Number
GenBank ID
Organism

ptb
15896327
NP_349676

Clostridium acetobutylicum

buk1
15896326
NP_349675

Clostridium acetobutylicum

buk2
20137415
Q97II1

Clostridium acetobutylicum

Step H—Amidohydrolase. EC 6.3.1.a/6.3.2.a Amide Synthases/Peptide Synthases.

The direct conversion of 6-aminocaproate to caprolactam as in step H can involve the formation of an intramolecular peptide bond. Ribosomes, which assemble amino acids into proteins during translation, are nature's most abundant peptide bond-forming catalysts. Nonribosomal peptide synthetases are peptide bond forming catalysts that do not involve messenger mRNA (Schwarzer et al., Nat Prod. Rep. 20:275-287 (2003)). Additional enzymes capable of forming peptide bonds include acyl-CoA synthetase from Pseudomonas chlororaphis (Abe et al., J Biol Chem 283:11312-11321 (2008)), gamma-Glutamylputrescine synthetase from E. coli (Kurihara et al., J Biol Chem 283:19981-19990 (2008)), and beta-lactam synthetase from Streptomyces clavuligerus (Bachmann et al., Proc Natl Acad Sci USA 95:9082-9086 (1998); Bachmann et al., Biochemistry 39:11187-11193 (2000); Miller et al., Nat Struct. Biol 8:684-689 (2001); Miller et al., Proc Natl Acad Sci USA 99:14752-14757 (2002); Tahlan et al., Antimicrob. Agents. Chemother. 48:930-939 (2004)).

Gene name
GI Number
GenBank ID
Organism

acsA
60650089
BAD90933

Pseudomonas chlororaphis

puuA
87081870
AAC74379

Escherichia coli

bls
41016784
Q9R8E3

Streptomyces clavuligerus

Step I—Spontaneous Cyclization.

The conversion of 6-aminocaproyl-CoA to caprolactam can occur by spontaneous cyclization. Because 6-aminocaproyl-CoA can cyclize spontaneously to caprolactam, it eliminates the need for a dedicated enzyme for this step. A similar spontaneous cyclization is observed with 4-aminobutyryl-CoA which forms pyrrolidinone (Ohsugi et al., J Biol Chem 256:7642-7651 (1981)).

Step J—6-Aminocaproyl-CoA Reductase (Aldehyde Forming).

The transformation of 6-aminocaproyl-CoA to 6-aminocaproate semialdehyde as in step J can involve an acyl-CoA dehydrogenases capable of reducing an acyl-CoA to its corresponding aldehyde. An EC 1.2.1.b oxidoreductase (acyl-CoA to aldehyde) provides suitable enzyme activity. Exemplary enzymes in this class are described herein and above.

Step K—HMDA Transaminase or HMDA Dehydrogenase.

EC 1.4.1.a Oxidoreductase Operating on Amino Acids.

Step K depicts a reductive animation and entails the conversion of 6-aminocaproate semialdehyde to hexamethylenediamine.

Gene

name
GI Number
GenBank ID
Organism

lysDH
13429872
BAB39707

Geobacillus stearothermophilus

lysDH
15888285
NP_353966

Agrobacterium tumefaciens

lysDH
74026644
AAZ94428

Achromobacter denitrificans

EC 2.6.1.a Aminotransferase.

Step K, in certain embodiments, can involve the transamination of a 6-aldehyde to an amine. This transformation can be catalyzed by gamma-aminobutyrate transaminase (GABA transaminase). One E. coli GABA transaminase is encoded by gabT and transfers an amino group from glutamate to the terminal aldehyde of succinyl semialdehyde (Bartsch et al., J. Bacteriol. 172:7035-7042 (1990)). The gene product of puuE catalyzes another 4-aminobutyrate transaminase in E. coli (Kurihara et al., J. Biol. Chem. 280:4602-4608 (2005)). GABA transaminases in Mus musculus, Pseudomonas fluorescens, and Sus scrofa have been shown to react with 6-aminocaproic acid (Cooper, Methods Enzymol. 113:80-82 (1985); Scott et al., J. Biol. Chem. 234:932-936 (1959)).

Gene name
GI Number
GenBank ID
Organism

ygjG
145698310
NP_417544

Escherichia coli

spuC
9946143
AAG03688

Pseudomonas aeruginosa

Step L—Adipyl-CoA Hydrolase, Adipyl-CoA Ligase, Adipyl-CoA Transferase or Phosphotransadipylase/Adipate Kinase.

Step L can involve adipyl-CoA synthetase (also referred to as adipate-CoA ligase), phosphotransadipylase/adipate kinase, adipyl-CoA:acetyl-CoA transferase, or adipyl-CoA hydrolase. From an energetic standpoint, it is desirable for the final step in the adipate synthesis pathway to be catalyzed by an enzyme or enzyme pair that can conserve the ATP equivalent stored in the thioester bond of adipyl-CoA. The product of the sucC and sucD genes of E. coli, or homologs thereof, can potentially catalyze the final transformation shown in FIG. 8 should they exhibit activity on adipyl-CoA. The sucCD genes naturally form a succinyl-CoA synthetase complex that catalyzes the formation of succinyl-CoA from succinate with the concaminant consumption of one ATP, a reaction which is reversible in vivo (Buck et al., Biochem. 24:6245-6252 (1985)). Given the structural similarity between succinate and adipate, that is, both are straight chain dicarboxylic acids, it is reasonable to expect some activity of the sucCD enzyme on adipyl-CoA. An enzyme exhibiting adipyl-CoA ligase activity can equivalently carry out the ATP-generating production of adipate from adipyl-CoA, here using AMP and PPi as cofactors, when operating in the opposite physiological. Exemplary CoA-ligases include the rat dicarboxylate-CoA ligase for which the sequence is yet uncharacterized (Vamecq et al., Biochem. J. 230:683-693 (1985)), either of the two characterized phenylacetate-CoA ligases from P. chrysogenum (Lamas-Maceiras et al., Biochem. J. 395, 147-155 (2005); Wang et al., Biochem. Biophy. Res. Commun. 360:453-458 (2007)), the phenylacetate-CoA ligase from Pseudomonas putida (Martinez-Blanco et al., J. Biol. Chem. 265:7084-7090 (1990)), and the 6-carboxyhexanoate-CoA ligase from Bacillus subtilis (Bower et al., J Bacteriol. 178:4122-4130 (1996)). The protein sequences for each of these exemplary gene products can be found using the following GI numbers and/or GenBank identifiers:

Gene name
GI Number
GenBank ID
Organism

sucC
16128703
NP_415256.1

Escherichia coli

sucD
1786949
AAC73823.1

Escherichia coli

Another option, using phosphotransadipylase/adipate kinase, is catalyzed by the gene products of buk1, buk2, and ptb from C. acetobutylicum (Walter et al., Gene 134:107-111 (1993); Huang et al., J. Mol. Microbiol. Biotechnol. 2:33-38 (2000)), or homologs thereof. The ptb gene encodes an enzyme that can convert butyryl-CoA into butyryl-phosphate, which is then converted to butyrate via either of the buk gene products with the concomitant generation of ATP. The analogous set of transformations, that is, conversion of adipyl-CoA to adipyl-phosphate followed by conversion of adipyl-phosphate to adipate, can be carried out by the buk1, buk2, and ptb gene products. The protein sequences for each of these exemplary gene products can be found using the following GI numbers and/or GenBank identifiers:

Alternatively, an acetyltransferase capable of transferring the CoA group from adipyl-CoA to acetate can be applied. Similar transformations are catalyzed by the gene products of cat1, cat2, and cat3 of Clostridium kluyveri which have been shown to exhibit succinyl-CoA, 4-hydroxybutyryl-CoA, and butyryl-CoA acetyltransferase activity, respectively (Sohling and Gottschalk, J. Bacteriol. 178:871-880 (1996); Seedorf et al., Proc. Natl. Acad. Sci. USA 105:2128-2133 (2008)). The protein sequences for each of these exemplary gene products can be found using the following GI numbers and/or GenBank identifiers:

Gene name
GI Number
GenBank ID
Organism

cat1
729048
P38946.1

Clostridium kluyveri

cat2
172046066
P38942.2

Clostridium kluyveri

cat3
146349050
EDK35586.1

Clostridium kluyveri

Finally, though not as desirable from an energetic standpoint, the conversion of adipyl-CoA to adipate can also be carried out by an acyl-CoA hydrolase or equivalently a thioesterase. The top E. coli gene candidate is tesB (Naggert et al., J. Biol. Chem. 266:11044-11050 (1991)), which shows high similarity to the human acot8, which is a dicarboxylic acid acetyltransferase with activity on adipyl-CoA (Westin et al., J. Biol. Chem. 280:38125-38132 (2005)). This activity has also been characterized in the rat liver (Deana, Biochem. Int. 26:767-773 (1992)). The protein sequences for each of these exemplary gene products can be found using the following GI numbers and/or GenBank identifiers:

Gene name
GI Number
GenBank ID
Organism

tesB
16128437
NP_414986

Escherichia coli

acot8
3191970
CAA15502

Homo sapiens

acot8
51036669
NP_570112

Rattus norvegicus

Other native candidate genes include tesA (Bonner and Bloch, J. Biol. Chem. 247:3123-3133 (1972)), ybgC (Kuznetsova et al., FEMS Microbiol. Rev. 29:263-279 (2005); Zhuang et al., FEBS Lett. 516:161-163 (2002)), paaI (Song et al., J. Biol. Chem. 281:11028-11038 (2006)), and ybdB (Leduc et al., J. Bacteriol. 189:7112-7126 (2007)). The protein sequences for each of these exemplary gene products can be found using the following GI numbers and/or GenBank identifiers:

Gene name
GI Number
GenBank ID
Organism

tesA
16128478
NP_415027

Escherichia coli

ybgC
16128711
NP_415264

Escherichia coli

paaI
16129357
NP_415914

Escherichia coli

ybdB
16128580
NP_415129

Escherichia coli

EC 2.8.3.a Coenzyme-A Transferase.

CoA transferases catalyze reversible reactions that involve the transfer of a CoA moiety from one molecule to another. For example, step L can be catalyzed by a adipyl-CoA transferase. One candidate enzyme for this step is the two-unit enzyme encoded by pcaI and pcaJ in Pseudomonas, which has been shown to have 3-oxoadipyl-CoA/succinate transferase activity (Kaschabek and Reineke, J. Bacteriol. 177:320-325 (1995); and Kaschabek. and Reineke, J. Bacteriol. 175:6075-6081 (1993)). Similar enzymes based on homology exist in Acinetobacter sp. ADP1 (Kowalchuk et al., Gene 146:23-30 (1994)) and Streptomyces coelicolor. Additional exemplary succinyl-CoA:3:oxoacid-CoA transferases are present in Helicobacter pylori (Corthesy-Theulaz et al., J. Biol. Chem. 272:25659-25667 (1997)) and Bacillus subtilis (Stols et al., Protein. Expr. Purif. 53:396-403 (2007)).

Gene name
GI Number
GenBank ID
Organism

pcaI
24985644
AAN69545.1

Pseudomonas putida

pcaJ
26990657
NP_746082.1

Pseudomonas putida

pcaI
50084858
YP_046368.1

Acinetobacter sp. ADP1

pcaJ
141776
AAC37147.1

Acinetobacter sp. ADP1

pcaI
21224997
NP_630776.1

Streptomyces coelicolor

pcaJ
21224996
NP_630775.1

Streptomyces coelicolor

HPAG1_0676
108563101
YP_627417

Helicobacter pylori

HPAG1_0677
108563102
YP_627418

Helicobacter pylori

ScoA
16080950
NP_391778

Bacillus subtilis

ScoB
16080949
NP_391777

Bacillus subtilis

A 3-oxoacyl-CoA transferase that can utilize acetate as the CoA acceptor is acetoacetyl-CoA transferase, encoded by the E. coli atoA (alpha subunit) and atoD (beta subunit) genes (Vanderwinkel et al., Biochem. Biophys. Res Commun. 33:902-908 (1968); Korolev et al., Acta Crystallogr. D Biol Crystallogr. 58:2116-2121 (2002)). This enzyme has also been shown to transfer the CoA moiety to acetate from a variety of branched and linear acyl-CoA substrates, including isobutyrate (Matthies et al., Appl Environ Microbiol 58:1435-1439 (1992)), valerate (Vanderwinkel et al., Biochem. Biophys. Res. Commun. 33:902-908 (1968)) and butanoate (Vanderwinkel et al., supra). Similar enzymes exist in Corynebacterium glutamicum ATCC 13032 (Duncan et al., Appl Environ Microbiol 68:5186-5190 (2002)), Clostridium acetobutylicum (Cary et al., Appl Environ Microbiol 56:1576-1583 (1990)), and Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci. Biotechnol Biochem. 71:58-68 (2007)).

Gene

name
GI Number
GenBank ID
Organism

atoA
2492994
P76459.1

Escherichia coli K12

atoD
2492990
P76458.1

Escherichia coli K12

actA
62391407
YP_226809.1

Corynebacterium glutamicum

ATCC 13032

cg0592
62389399
YP_224801.1

Corynebacterium glutamicum

ATCC 13032

ctfA
15004866
NP_149326.1

Clostridium acetobutylicum

ctfB
15004867
NP_149327.1

Clostridium acetobutylicum

ctfA
31075384
AAP42564.1

Clostridium

saccharoperbutylacetonicum

ctfB
31075385
AAP42565.1

Clostridium

saccharoperbutylacetonicum

The above enzymes may also exhibit the desired activities on adipyl-CoA and adipate for step L. Nevertheless, additional exemplary transferase candidates are catalyzed by the gene products of cat1, cat2, and cat3 of Clostridium kluyveri which have been shown to exhibit succinyl-CoA, 4-hydroxybutyryl-CoA, and butyryl-CoA transferase activity, respectively (Seedorf et al., Proc. Natl. Acad. Sci U.S.A. 105:2128-2133 (2008); Sohling et al., Eur. J Biochem. 212:121-127 (1993); Sohling et al., J Bacteriol. 178:871-880 (1996)).

Gene name
GI Number
GenBank ID
Organism

cat1
729048
P38946.1

Clostridium kluyveri

cat2
172046066
P38942.2

Clostridium kluyveri

cat3
146349050
EDK35586.1

Clostridium kluyveri

Gene name
GI Number
GenBank ID
Organism

gctA
559392
CAA57199.1

Acidaminococcus fermentans

gctB
559393
CAA57200.1

Acidaminococcus fermentans

Example XIII
Methacrylic Acid Synthesis Enzymes

This Example provides genes that can be used for conversion of succinyl-CoA to methacrylic acid as depicted in the pathways of FIG. 9.

FIG. 9. depicts 3-Hydroxyisobutyrate and methacrylic acid production are carried out by the following enzymes: A) Methylmalonyl-CoA mutase, B) Methylmalonyl-CoA epimerase, C) Methylmalonyl-CoA reductase (aldehyde forming), D) Methylmalonate semialdehyde reductase, E) 3-hydroxyisobutyrate dehydratase, F) Methylmalonyl-CoA reductase (alcohol forming).

Step A—Methylmalonyl-CoA Mutase (Designated as EMA2).

Methylmalonyl-CoA mutase (MCM) (EMA2) (EC 5.4.99.2) is a cobalamin-dependent enzyme that converts succinyl-CoA to methylmalonyl-CoA. In E. coli, the reversible adenosylcobalamin-dependent mutase participates in a three-step pathway leading to the conversion of succinate to propionate (Haller et al., Biochemistry 39:4622-4629 (2000)). Overexpression of the EMA2 gene candidate along with the deletion of YgfG can be used to prevent the decarboxylation of methylmalonyl-CoA to propionyl-CoA and to maximize the methylmalonyl-CoA available for MAA synthesis. EMA2 is encoded by genes scpA in Escherichia coli (Bobik and Rasche, Anal. Bioanal. Chem. 375:344-349 (2003); Haller et al., Biochemistry 39:4622-4629 (2000)) and mutA in Homo sapiens (Padovani and Banerjee, Biochemistry 45:9300-9306 (2006)). In several other organisms EMA2 contains alpha and beta subunits and is encoded by two genes. Exemplary gene candidates encoding the two-subunit protein are Propionibacterium fredenreichii sp. shermani mutA and mutB (Korotkova and Lidstrom, J. Biol. Chem. 279:13652-13658 (2004)), Methylobacterium extorquens mcmA and mcmB (Korotkova and Lidstrom, supra, 2004), and Ralstonia eutropha sbm1 and sbm2 (Peplinski et al., Appl. Microbiol. Biotech. 88:1145-59 (2010)). Additional enzyme candidates identified based on high homology to the E. coli spcA gene product are also listed below.

Protein
GenBank ID
GI Number
Organism

scpA
NP_417392.1
16130818

Escherichia coli K12

mutA
P22033.3
67469281

Homo sapiens

mutA
P11652.3
127549

Propionibacterium fredenreichii

sp. shermanii

mutB
P11653.3
127550

Propionibacterium fredenreichii

sp. shermanii

mcmA
Q84FZ1
75486201

Methylobacterium extorquens

mcmB
Q6TMA2
75493131

Methylobacterium extorquens

Sbm1
YP_724799.1
113866310

Ralstonia eutropha H16

Sbm2
YP_726418.1
113867929

Ralstonia eutropha H16

sbm
NP_838397.1
30064226

Shigella flexneri

SARI_04585
ABX24358.1
160867735

Salmonella enterica

YfreA_01000861
ZP_00830776.1
77975240

Yersina frederiksenii

These sequences can be used to identify homologue proteins in GenBank or other databases through sequence similarity searches (for example, BLASTp). The resulting homologue proteins and their corresponding gene sequences provide additional exogenous DNA sequences for transformation into E. coli or other suitable host microorganisms to generate production hosts. Additional gene candidates include the following, which were identified based on high homology to the E. coli spcA gene product.

There further exists evidence that genes adjacent to the EMA2 catalytic genes contribute to maximum activity. For example, it has been demonstrated that the meaB gene from M. extorquens forms a complex with EMA2, stimulates in vitro mutase activity, and possibly protects it from irreversible inactivation (Korotkova and Lidstrom, J. Biol. Chem. 279:13652-13658 (2004)). The M. extorquens meaB gene product is highly similar to the product of the E. coli argK gene (BLASTp: 45% identity, e-value: 4e−67), which is adjacent to scpA on the chromosome. No sequence for a meaB homolog in P. freudenreichii is catalogued in GenBank. However, the Propionibacterium acnes KPA171202 gene product, YP_055310.1, is 51% identical to the M. extorquens meaB protein and its gene is also adjacent to the EMA2 gene on the chromosome. A similar gene is encoded by H16_B1839 of Ralstonia eutropha H16.

Gene
GenBank ID
GI Number
Organism

argK
AAC75955.1
1789285

Escherichia coli K12

PPA0597
YP_055310.1
50842083

Propionibacterium acnes

KPA171202
2QM8_B
158430328

Methylobacterium

extorquens

H16_B1839
YP_841351.1
116695775

Ralstonia eutropha H16

E. coli can synthesize adenosylcobalamin, a necessary cofactor for this reaction, only when supplied with the intermediates cobinamide or cobalamin (Lawrence and Roth. J. Bacteriol. 177:6371-6380 (1995); Lawrence and Roth, Genetics 142:11-24 (1996)). Alternatively, the ability to synthesize cobalamins de novo has been conferred upon E. coli following the expression of heterologous genes (Raux et al., J. Bacteriol. 178:753-767 (1996)).

Alternatively, isobutyryl-CoA mutase (ICM) (EC 5.4.99.13) could catalyze the proposed transformation shown in FIG., step B. ICM is a cobalamin-dependent methylmutase in the EMA2 family that reversibly rearranges the carbon backbone of butyryl-CoA into isobutyryl-CoA (Ratnatilleke et al., J. Biol. Chem. 274:31679-31685 (1999)). A recent study of a novel ICM in Methylibium petroleiphilum, along with previous work, provides evidence that changing a single amino acid near the active site alters the substrate specificity of the enzyme (Ratnatilleke et al., J. Biol. Chem. 274:31679-31685 (1999); Rohwerder et al., Appl. Environ. Microbiol. 72:4128-4135. (2006)). This indicates that, if a native enzyme is unable to catalyze or exhibits low activity for the conversion of 4HB-CoA to 3HIB-CoA, the enzyme can be rationally engineered to increase this activity. Exemplary ICM genes encoding homodimeric enzymes include icmA in Streptomyces coelicolor A3 (Alhapel et al., Proc. Natl. Acad. Sci. USA 103:12341-12346 (2006)) and Mpe_B0541 in Methylibium petroleiphilum PM1 (Ratnatilleke et al., J. Biol. Chem. 274:31679-31685 (1999); Rohwerder et al., Appl. Environ. Microbiol. 72:4128-4135 (2006)). Genes encoding heterodimeric enzymes include icm and icmB in Streptomyces cinnamonensis (Ratnatilleke et al., J. Biol. Chem. 274:31679-31685 (1999); Vrijbloed et al., J. Bacteriol. 181:5600-5605. (1999); Zerbe-Burkhardt et al., J. Biol. Chem. 273:6508-6517 (1998)). Enzymes encoded by icmA and icmB genes in Streptomyces avermitilis MA-4680 show high sequence similarity to known ICMs. These genes/proteins are identified below.

Gene
GenBank ID
GI Number
Organism

icmA
CAB40912.1
4585853

Streptomyces coelicolor A3(2)

Mpe_B0541
YP_001023546.1
124263076

Methylibium petroleiphilum

PM1

icm
AAC08713.1
3002492

Streptomyces cinnamonensis

icmB
CAB59633.1
6137077

Streptomyces cinnamonensis

icmA
NP_824008.1
29829374

Streptomyces avermitilis

icmB
NP_824637.1
29830003

Streptomyces avermitilis

Step B—Methylmalonyl-CoA Epimerase (Designated as EMA3).

Methylmalonyl-CoA epimerase (MMCE) (EMA3) is the enzyme that interconverts (R)-methylmalonyl-CoA and (S)-methylmalonyl-CoA. EMA3 is an essential enzyme in the breakdown of odd-numbered fatty acids and of the amino acids valine, isoleucine, and methionine. EMA3 activity is not believed to be encoded in the E. coli genome (Boynton et al., J. Bacteriol. 178:3015-3024 (1996)), but is present in other organisms such as Homo sapiens (YqjC) (Fuller and Leadlay, Biochem. J. 213:643-650 (1983)), Rattus norvegicus (Mcee) (Bobik and Rasche, J. Biol. Chem. 276:37194-37198 (2001)), Propionibacterium shermanii (AF454511) (Fuller. and Leadlay, Biochem. J. 213:643-650 (1983); Haller et al., Biochemistry 39:4622-4629 (2000); McCarthy et al., Structure 9:637-646.2001)) and Caenorhabditis elegans (mmce) (Kuhnl et al., FEBS J. 272:1465-1477 (2005)). An additional gene candidate, AE016877 in Bacillus cereus, has high sequence homology to other characterized enzymes. This enzymatic step may or may not be necessary depending upon the stereospecificity of the enzyme or enzymes used for the conversion of methylmalonyl-CoA to 3-HIB. These genes/proteins are described below.

Gene
GenBank ID
GI Number
Organism

YqjC
NP_390273
255767522

Bacillus subtilis

MCEE
Q96PE7.1
50401130

Homo sapiens

Mcee_predicted
NP_001099811.1
157821869

Rattus norvegicus

AF454511
AAL57846.1
18042135

Propionibacterium

Mmce
AAT92095.1
51011368

Caenorhabditis

elegans

AE016877
AAP08811.1
29895524

Bacillus cereus

ATCC 14579

Step C—Methylmalonyl-CoA Reductase (Aldehyde Forming) (Designated as EMA4).

The reduction of methylmalonyl-CoA to its corresponding aldehyde, methylmalonate semialdehyde, is catalyzed by a CoA-dependent aldehyde dehydrogenase (EC 1.2.1.-). Conversion of methylmalonyl-CoA to methylmalonic semialdehyde, is accomplished by a CoA-dependent aldehyde dehydrogenase. An enzyme encoded by a malonyl-CoA reductase gene from Sulfolobus tokodaii (Alber et. al., J. Bacteriol. 188(24):8551-8559 (2006)), has been shown to catalyze the conversion of methylmalonyl-CoA to its corresponding aldehyde (WO2007141208). A similar enzyme exists in Metallosphaera sedula (Alber et. al., J. Bacteriol. 188(24):8551-8559 (2006)). Several additional CoA dehydrogenases are capable also of reducing an acyl-CoA to its corresponding aldehyde. The reduction of methylmalonyl-CoA to its corresponding aldehyde, methylmalonate semialdehyde, is catalyzed by a CoA-dependent aldehyde dehydrogenase. Exemplary enzymes include fatty acyl-CoA reductase, succinyl-CoA reductase (EC 1.2.1.76), acetyl-CoA reductase and butyryl-CoA reductase. Exemplary fatty acyl-CoA reductase enzymes are encoded by acr1 of Acinetobacter calcoaceticus (Reiser and Somerville. J Bacteriol. 179:2969-2975 (1997)), and Acinetobacter sp. M-1 fatty acyl-CoA reductase (Ishige et al., Appl. Environ. Microbiol. 68:1192-1195 (2002)). Also known is a CoA- and NADP-dependent succinate semialdehyde dehydrogenase (also referred to as succinyl-CoA reductase) encoded by the sucD gene in Clostridium kluyveri (Sohling and Gottschalk, J. Bacteriol. 178:871-880 (1996); Sohling and Gottschalk, J. Bacteriol. 178:871-880 (1996)) and sucD of P. gingivalis (Takahashi, J. Bacteriol 182:4704-4710 (2000)). Additional succinyl-CoA reductase enzymes participate in the 3-hydroxypropionate/4-hydroxybutyrate cycle of thermophilic archaea including Metallosphaera sedula (Berg et al., Science 318:1782-1786 (2007)) and Thermoproteus neutrophilus (Ramos-Vera et al., J Bacteriol, 191:4286-4297 (2009)). The M. sedula enzyme, encoded by Msed_0709, is strictly NADPH-dependent and also has malonyl-CoA reductase activity. The T. neutrophilus enzyme is active with both NADPH and NADH. The enzyme acylating acetaldehyde dehydrogenase in Pseudomonas sp, encoded by bphG, is also a good candidate as it has been demonstrated to oxidize and acylate acetaldehyde, propionaldehyde, butyraldehyde, formaldehyde and the branched-chain compound isobutyraldehyde (Powlowski et al., J. Bacteriol. 175:377-385 (1993)). In addition to reducing acetyl-CoA to ethanol, the enzyme encoded by adhE in Leuconostoc mesenteroides has been shown to oxidize the branched chain compound isobutyraldehyde to isobutyryl-CoA (Kazahaya, J. Gen. Appl. Microbiol. 18:43-55 (1972); and Koo et al., Biotechnol Lett. 27:505-510 (2005)). Butyraldehyde dehydrogenase catalyzes a similar reaction, conversion of butyryl-CoA to butyraldehyde, in solventogenic organisms such as Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci Biotechnol Biochem., 71:58-68 (2007)).

GI

Protein
GenBank ID
Number
Organism

acr1
YP_047869.1
50086359

Acinetobacter calcoaceticus

acr1
AAC45217
1684886

Acinetobacter baylyi

acr1
BAB85476.1
18857901

Acinetobacter sp. Strain M-1

MSED_0709
YP_001190808.1
146303492

Metallosphaera sedula

Tneu _0421

Thermoproteus neutrophilus

sucD
P38947.1
172046062

Clostridium kluyveri

sucD
NP_904963.1
34540484

Porphyromonas gingivalis

bphG
BAA03892.1
425213

Pseudomonas sp

adhE
AAV66076.1
55818563

Leuconostoc mesenteroides

bld
AAP42563.1
31075383

Clostridium

saccharoperbutylacetonicum

An additional enzyme type that converts an acyl-CoA to its corresponding aldehyde is malonyl-CoA reductase which transforms malonyl-CoA to malonic semialdehyde. Malonyl-CoA reductase is a key enzyme in autotrophic carbon fixation via the 3-hydroxypropionate cycle in thermoacidophilic archaeal bacteria (Berg, Science 318:1782-1786 (2007); and Thauer, Science 318:1732-1733 (2007)). The enzyme utilizes NADPH as a cofactor and has been characterized in Metallosphaera and Sulfolobus sp. (Alber et al., J. Bacteriol. 188:8551-8559 (2006); and Hugler, J. Bacteriol. 184:2404-2410 (2002)). The enzyme is encoded by Msed_0709 in Metallosphaera sedula (Alber et al., J. Bacteriol. 188:8551-8559 (2006); and Berg, Science 318:1782-1786 (2007)). A gene encoding a malonyl-CoA reductase from Sulfolobus tokodaii was cloned and heterologously expressed in E. coli (Alber et al., J. Bacteriol 188:8551-8559 (2006). This enzyme has also been shown to catalyze the conversion of methylmalonyl-CoA to its corresponding aldehyde (WO2007141208 (2007)). Although the aldehyde dehydrogenase functionality of these enzymes is similar to the bifunctional dehydrogenase from Chloroflexus aurantiacus, there is little sequence similarity. Both malonyl-CoA reductase enzyme candidates have high sequence similarity to aspartate-semialdehyde dehydrogenase, an enzyme catalyzing the reduction and concurrent dephosphorylation of aspartyl-4-phosphate to aspartate semialdehyde. Additional gene candidates can be found by sequence homology to proteins in other organisms including Sulfolobus solfataricus and Sulfolobus acidocaldarius and have been listed below. Yet another candidate for CoA-acylating aldehyde dehydrogenase is the ald gene from Clostridium beijerinckii (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999). This enzyme has been reported to reduce acetyl-CoA and butyryl-CoA to their corresponding aldehydes. This gene is very similar to eutE that encodes acetaldehyde dehydrogenase of Salmonella typhimurium and E. coli (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999).

Gene
GenBank ID
GI Number
Organism

Msed_0709
YP_001190808.1
146303492

Metallosphaera sedula

Mcr
NP_378167.1
15922498

Sulfolobus tokodaii

asd-2
NP_343563.1
15898958

Sulfolobus solfataricus

Saci_2370
YP_256941.1
70608071

Sulfolobus acidocaldarius

Ald
AAT66436
49473535

Clostridium beijerinckii

eutE
AAA80209
687645

Salmonella typhimurium

eutE
P77445
2498347

Escherichia coli

A bifunctional enzyme with acyl-CoA reductase and alcohol dehydrogenase activity can directly convert methylmalonyl-CoA to 3-HIB. Exemplary bifunctional oxidoreductases that convert an acyl-CoA to alcohol include those that transform substrates such as acetyl-CoA to ethanol (for example, adhE from E. coli (Kessler et al., FEBS. Lett. 281:59-63 (1991))) and butyryl-CoA to butanol (for example, adhE2 from C. acetobutylicum (Fontaine et al., J. Bacteriol. 184:821-830 (2002)). The C. acetobutylicum enzymes encoded by bdh I and bdh II (Walter, et al., J. Bacteriol. 174:7149-7158 (1992)), reduce acetyl-CoA and butyryl-CoA to ethanol and butanol, respectively. In addition to reducing acetyl-CoA to ethanol, the enzyme encoded by adhE in Leuconostoc mesenteroides has been shown to oxide the branched chain compound isobutyraldehyde to isobutyryl-CoA (Kazahaya et al., J. Gen. Appl. Microbiol. 18:43-55 (1972); Koo et al., Biotechnol Lett, 27:505-510 (2005)). Another exemplary enzyme can convert malonyl-CoA to 3-HP. An NADPH-dependent enzyme with this activity has characterized in Chloroflexus aurantiacus where it participates in the 3-hydroxypropionate cycle (Hugler et al., J Bacteriol, 184:2404-2410 (2002); Strauss et al., Eur J Biochem, 215:633-643 (1993)). This enzyme, with a mass of 300 kDa, is highly substrate-specific and shows little sequence similarity to other known oxidoreductases (Hugler et al., supra). No enzymes in other organisms have been shown to catalyze this specific reaction; however there is bioinformatic evidence that other organisms may have similar pathways (Klatt et al., Env Microbiol, 9:2067-2078 (2007)). Enzyme candidates in other organisms including Roseiflexus castenholzii, Erythrobacter sp. NAP1 and marine gamma proteobacterium HTCC2080 can be inferred by sequence similarity.

GI

Protein
GenBank ID
Number
Organism

adhE
NP_415757.1
16129202

Escherichia coli

adhE2
AAK09379.1
12958626

Clostridium

acetobutylicum

adhE
AAV66076.1
55818563

Leuconostoc

mesenteroides

bdh I
NP_349892.1
15896543

Clostridium

acetobutylicum

bdh II
NP_349891.1
15896542

Clostridium

acetobutylicum

Mcr
AAS20429.1
42561982

Chloroflexus

aurantiacus

Rcas_2929
YP_001433009.1
156742880

Roseiflexus

castenholzii

NAP1_02720
ZP_01039179.1
85708113

Erythrobacter

sp. NAP1

MGP2080_00535
ZP_01626393.1
119504313

marine gamma

proteobacterium

HTCC2080

Step D—Methylmalonate Semialdehyde Reductase (Designated as EMA5).

The reduction of methylmalonate semialdehyde to 3-HIB is catalyzed by EMA5 or 3-HIB dehydrogenase. This enzyme participates in valine, leucine and isoleucine degradation and has been identified in bacteria, eukaryotes, and mammals. The enzyme encoded by P84067 from Thermus thermophilus HB8 has been structurally characterized (Lokanath et al., J. Mol. Biol. 352:905-917 (2005)). The reversibility of the human 3-HIB dehydrogenase was demonstrated using isotopically-labeled substrate (Manning and Pollitt, Biochem. J. 231:481-484 (1985)). Additional genes encoding this enzyme include 3hidh in Homo sapiens (Hawes et al., Methods Enzymol. 324:218-228 (2000)) and Oryctolagus cuniculus (Chowdhury et al., Biosci. Biotechnol. Biochem. 60:2043-2047 (1996); Hawes et al., Methods Enzymol. 324:218-228 (2000)), mmsb in Pseudomonas aeruginosa, and dhat in Pseudomonas putida (Aberhart and Hsu J Chem. Soc. [Perkin 1] 6:1404-1406 (1979); Chowdhury et al., Biosci. Biotechnol. Biochem. 67:438-441 (2003); Chowdhury et al., Biosci. Biotechnol. Biochem. 60:2043-2047 (1996)). Several 3-HIB dehydrogenase enzymes have been characterized in the reductive direction, including mmsB from Pseudomonas aeruginosa (Gokarn et al., U.S. Pat. No. 7,393,676 (2008)) and mmsB from Pseudomonas putida.

Protein
GenBank ID
GI Number
Organism

P84067
P84067
75345323

Thermus thermophilus

3hidh
P31937.2
12643395

Homo sapiens

3hidh
P32185.1
416872

Oryctolagus cuniculus

mmsB
NP_746775.1
26991350

Pseudomonas putida

mmsB
P28811.1
127211

Pseudomonas aeruginosa

dhat
Q59477.1
2842618

Pseudomonas putida

Step E—3-HIB Dehydratase (Designated as EMA6).

The dehydration of 3-HIB to MAA is catalyzed by an enzyme with EMA6 activity (EC 4.2.1.-). The final step involves the dehydration of 3-HIB to MAA The dehydration of 3-HIB to MAA is catalyzed by an enzyme with EMA6 activity. Although no direct evidence for this specific enzymatic transformation has been identified, most dehydratases catalyze the alpha,beta-elimination of water, which involves activation of the alpha-hydrogen by an electron-withdrawing carbonyl, carboxylate, or CoA-thiol ester group and removal of the hydroxyl group from the beta-position (Buckel and Barker, J Bacteriol. 117:1248-1260 (1974); Martins et al, Proc. Natl. Acad. Sci. USA 101:15645-15649 (2004)). This is the exact type of transformation proposed for the final step in the methacrylate pathway. In addition, the proposed transformation is highly similar to the 2-(hydroxymethyl)glutarate dehydratase of Eubacterium barkeri, which can catalyze the conversion of 2-hydroxymethyl glutarate to 2-methylene glutarate. This enzyme has been studied in the context of nicotinate catabolism and is encoded by hmd (Alhapel et al., Proc. Natl. Acad. Sci. USA 103:12341-12346 (2006)). Similar enzymes with high sequence homology are found in Bacteroides capillosus, Anaerotruncus colihominis, and Natranaerobius thermophilius. Several enzymes are known to catalyze the alpha, beta elimination of hydroxyl groups. Exemplary enzymes include 2-(hydroxymethyl)glutarate dehydratase (EC 4.2.1.-), fumarase (EC 4.2.1.2), 2-keto-4-pentenoate dehydratase (EC 4.2.1.80), citramalate hydrolyase and dimethylmaleate hydratase.

2-(Hydroxymethyl)glutarate dehydratase is a [4Fe-4S]-containing enzyme that dehydrates 2-(hydroxymethyl)glutarate to 2-methylene-glutarate, studied for its role in nicontinate catabolism in Eubacterium barkeri (formerly Clostridium barkeri) (Alhapel et al., Proc Natl Acad Sci USA 103:12341-12346 (2006)). Similar enzymes with high sequence homology are found in Bacteroides capillosus, Anaerotruncus colihominis, and Natranaerobius thermophilius. These enzymes are also homologous to the alpha- and beta-subunits of [4Fe-4S]-containing bacterial serine dehydratases, for example, E. coli enzymes encoded by tdcG, sdhB, and sdaA). An enzyme with similar functionality in E. barkeri is dimethylmaleate hydratase, a reversible Fe2+-dependent and oxygen-sensitive enzyme in the aconitase family that hydrates dimethylmaeate to form (2R,3S)-2,3-dimethylmalate. This enzyme is encoded by dmdAB (Alhapel et al., Proc Natl Acad Sci USA 103:12341-6 (2006); Kollmann-Koch et al., Hoppe Seylers. Z. Physiol Chem. 365:847-857 (1984)).

Protein
GenBank ID
GI Number
Organism

Hmd
ABC88407.1
86278275

Eubacterium barkeri

BACCAP_02294
ZP_02036683.1
154498305

Bacteroides capillosus

ANACOL_02527
ZP_02443222.1
167771169

Anaerotruncus

NtherDRAFT_2368
ZP_02852366.1
169192667

Natranaerobius

dmdA
ABC88408
86278276

Eubacterium barkeri

dmdB
ABC88409
86278277

Eubacterium barkeri

Fumarate hydratase enzymes, which naturally catalyze the reversible hydration of fumarate to malate. Although the ability of fumarate hydratase to react on branched substrates with 3-oxobutanol as a substrate has not been described, a wealth of structural information is available for this enzyme and other researchers have successfully engineered the enzyme to alter activity, inhibition and localization (Weaver, Acta Crystallogr. D Biol. Crystallogr. 61:1395-1401 (2005)). E. coli has three fumarases: FumA, FumB, and FumC that are regulated by growth conditions. FumB is oxygen sensitive and only active under anaerobic conditions. FumA is active under microanaerobic conditions, and FumC is the only active enzyme in aerobic growth (Tseng et al., J. Bacteriol. 183:461-467 (2001); Woods et al., Biochem. Biophys. Acta 954:14-26 (1988); Guest et al., J Gen Microbiol 131:2971-2984 (1985)). Exemplary enzyme candidates include those encoded by fumC from Escherichia coli (Estevez et al., Protein Sci. 11:1552-1557 (2002); Hong and Lee, Biotechnol. Bioprocess Eng. 9:252-255 (2004); Rose and Weaver, Proc. Natl. Acad. Sci. USA 101:3393-3397 (2004)), and enzymes found in Campylobacter jejuni (Smith et al., Int. J. Biochem. Cell Biol. 31:961-975 (1999)), Thermus thermophilus (Mizobata et al., Arch. Biochem. Biophys. 355:49-55 (1998)), and Rattus norvegicus (Kobayashi et al., J. Biochem. 89:1923-1931 (1981)). Similar enzymes with high sequence homology include fum1 from Arabidopsis thaliana and fumC from Corynebacterium glutamicum. The MmcBC fumarase from Pelotomaculum thermopropionicum is another class of fumarase with two subunits (Shimoyama et al., FEMS Microbiol Lett. 270:207-213 (2007)).

Protein
GenBank ID
GI Number
Organism

fumA
NP_416129.1
16129570

Escherichia coli

fumB
NP_418546.1
16131948

Escherichia coli

fumC
NP_416128.1
16129569

Escherichia coli

fumC
O69294
9789756

Campylobacter jejuni

fumC
P84127
75427690

Thermus thermophilus

fumH
P14408
120605

Rattus norvegicus

fum1
P93033
39931311

Arabidopsis thaliana

fumC
Q8NRN8
39931596

Corynebacterium glutamicum

MmcB
YP_001211906
147677691

Pelotomaculum

MmcC
YP_001211907
147677692

Pelotomaculum

Dehydration of 4-hydroxy-2-oxovalerate to 2-oxopentenoate is catalyzed by 4-hydroxy-2-oxovalerate hydratase (EC 4.2.1.80). This enzyme participates in aromatic degradation pathways and is typically co-transcribed with a gene encoding an enzyme with 4-hydroxy-2-oxovalerate aldolase activity. Exemplary gene products are encoded by mhpD of E. coli (Ferrandez et al., J Bacteriol. 179:2573-2581 (1997); Pollard et al., Eur J Biochem. 251:98-106 (1998)), todG and cmtF of Pseudomonas putida (Lau et al., Gene 146:7-13 (1994); Eaton, J Bacteriol. 178:1351-1362 (1996)), cnbE of Comamonas sp. CNB-1 (Ma et al., Appl Environ Microbiol 73:4477-4483 (2007)) and mhpD of Burkholderia xenovorans (Wang et al., FEBS J 272:966-974 (2005)). A closely related enzyme, 2-oxohepta-4-ene-1,7-dioate hydratase, participates in 4-hydroxyphenylacetic acid degradation, where it converts 2-oxo-hept-4-ene-1,7-dioate (OHED) to 2-oxo-4-hydroxy-hepta-1,7-dioate using magnesium as a cofactor (Burks et al., J. Am. Chem. Soc. 120: (1998)). OHED hydratase enzyme candidates have been identified and characterized in E. coli C (Roper et al., Gene 156:47-51 (1995); Izumi et al., J Mol. Biol. 370:899-911 (2007)) and E. coli W (Prieto et al., J Bacteriol. 178:111-120 (1996)). Sequence comparison reveals homologs in a wide range of bacteria, plants and animals. Enzymes with highly similar sequences are contained in Klebsiella pneumonia (91% identity, eval=2e−138) and Salmonella enterica (91% identity, eval=4e−138), among others.

GenBank

Gene
Accession No.
GI No.
Organism

mhpD
AAC73453.2
87081722

Escherichia coli

cmtF
AAB62293.1
1263188

Pseudomonas putida

todG
AAA61942.1
485738

Pseudomonas putida

cnbE
YP_001967714.1
190572008

Comamonas sp. CNB-1

mhpD
Q13VU0
123358582

Burkholderia xenovorans

hpcG
CAA57202.1
556840

Escherichia coli C

hpaH
CAA86044.1
757830

Escherichia coli W

hpaH
ABR80130.1
150958100

Klebsiella pneumoniae

Sari_01896
ABX21779.1
160865156

Salmonella enterica

Another enzyme candidate is citramalate hydrolyase (EC 4.2.1.34), an enzyme that naturally dehydrates 2-methylmalate to mesaconate. This enzyme has been studied in Methanocaldococcus jannaschii in the context of the pyruvate pathway to 2-oxobutanoate, where it has been shown to have a broad substrate specificity (Drevland et al., J Bacteriol. 189:4391-4400 (2007)). This enzyme activity was also detected in Clostridium tetanomorphum, Morganella morganii, Citrobacter amalonaticus where it is thought to participate in glutamate degradation (Kato et al., Arch. Microbiol 168:457-463 (1997)). The M. jannaschii protein sequence does not bear significant homology to genes in these organisms.

Protein
GenBank ID
GI Number
Organism

leuD
Q58673.1
3122345

Methanocaldococcus jannaschii

Dimethylmaleate hydratase (EC 4.2.1.85) is a reversible Fe²⁺-dependent and oxygen-sensitive enzyme in the aconitase family that hydrates dimethylmaeate to form (2R,3S)-2,3-dimethylmalate. This enzyme is encoded by dmdAB in Eubacterium barkeri (Alhapel et al., supra; Kollmann-Koch et al., Hoppe Seylers. Z. Physiol Chem. 365:847-857 (1984)).

Protein
GenBank ID
GI Number
Organism

dmdA
ABC88408
86278276

Eubacterium barkeri

dmdB
ABC88409.1
86278277

Eubacterium barkeri

Step F—Methylmalonyl-CoA Reductase (Alcohol Forming) (Designated as EMA7).

Step F can involve a combined Alcohol/Aldehyde dehydrogenase (EC 1.2.1.-). Methylmalonyl-CoA can be reduced to 3-HIB in one step by a multifunctional enzyme with dual acyl-CoA reductase and alcohol dehydrogenase activity. Although the direct conversion of methylmalonyl-CoA to 3-HIB has not been reported, this reaction is similar to the common conversions such as acetyl-CoA to ethanol and butyryl-CoA to butanol, which are catalyzed by CoA-dependent enzymes with both alcohol and aldehyde dehydrogenase activities. Gene candidates include the E. coli adhE (Kessler et al., FEBS Lett. 281:59-63 (1991)) and C. acetobutylicum bdh I and bdh II (Walter, et al., J. Bacteriol. 174:7149-7158 (1992)), which can reduce acetyl-CoA and butyryl-CoA to ethanol and butanol, respectively. In addition to reducing acetyl-CoA to ethanol, the enzyme encoded by adhE in Leuconostoc mesenteroides has been shown to oxide the branched chain compound isobutyraldehyde to isobutyryl-CoA (Kazahaya et al., J. Gen. Appl. Microbiol. 18:43-55 (1972); Koo et al., Biotechnol. Lett. 27:505-510 (2005)). An additional candidate enzyme for converting methylmalonyl-CoA directly to 3-HIB is encoded by a malonyl-CoA reductase from Chloroflexus aurantiacus (Hagler, et al., J. Bacteriol. 184(9):2404-2410 (2002).

Protein
GenBank ID
GI Number
Organism

Mcr
YP_001636209.1
163848165

Chloroflexus aurantiacus

adhE
NP_415757.1
16129202

Escherichia coli

bdh I
NP_349892.1
15896543

Clostridium acetobutylicum

bdh II
NP_349891.1
15896542

Clostridium acetobutylicum

adhE
AAV66076.1
55818563

Leuconostoc mesenteroides

Example XIV
Methacrylic Acid and 2-Hydroxyisobutyric Synthesis Enzymes

This Example provides genes that can be used for conversion of acetyl-CoA to methacrylic acid and 2-hydroxyisobutyric as depicted in the pathways of FIG. 10. FIG. 10. Exemplary pathways enabling production of 2-hydroxyisobutyrate and methacrylic acid from acetyl-CoA. 2-Hydroxyisobutyrate and methacrylic acid production are carried out by the following enzymes: A) acetyl-CoA:acetyl-CoA acyltransferase, B) acetoacetyl-CoA reductase (ketone reducing), C) 3-hydroxybutyrl-CoA mutase, D) 2-hydroxyisobutyryl-CoA dehydratase, E) methacrylyl-CoA synthetase, hydrolase, or transferase, F) 2-hydroxyisobutyryl-CoA synthetase, hydrolase, or transferase.

MAA biosynthesis can proceed from acetyl-CoA in a minimum of five enzymatic steps (see FIG. 10). In this pathway, two molecules of acetyl-CoA are combined to form acetoacetyl-CoA, which is then reduced to 3-hydroxybutyryl-CoA. Alternatively, 4-hydroxybutyryl-CoA can be converted to 3-hydroxybutyryl-CoA by way of 4-hydroxybutyryl-CoA dehydratase and crotonase (Martins et al., Proc. Nat. Acad. Sci. USA 101(44) 15645-15649 (2004); Jones and Woods, Microbiol. Rev. 50:484-524 (1986); Berg et al., Science 318(5857) 1782-1786 (2007)). A methylmutase then rearranges the carbon backbone of 3-hydroxybutyryl-CoA to 2-hydroxyisobutyryl-CoA, which is then dehydrated to form methacrylyl-CoA. Alternatively, 2-hydroxyisobutyryl-CoA can be converted to 2-hydroxyisobutyrate, secreted, and recovered as product. The final step converting methacrylyl-CoA to MAA can be performed by a single enzyme shown in the figure or a series of enzymes.

A) Acetyl-CoA:Acetyl-CoA Acyltransferase.

Step A involves acetoacetyl-CoA thiolase (EC 2.3.1.9). The formation of acetoacetyl-CoA from two acetyl-CoA units is catalyzed by acetyl-CoA thiolase. This enzyme is native to E. coli, encoded by gene atoB, and typically operates in the acetoacetate-degrading direction during fatty acid oxidation (Duncombe and Frerman, Arch. Biochem. Biophys. 176:159-170 (1976); Frerman and Duncombe, Biochim. Biophys. Acta 580:289-297 (1979)). The gene thlA from Clostridium acetobutylicum was engineered into an isopropanol-producing strain of E. coli (Hanai et al., Appl. Environ. Microbiol. 73:7814-7818 (2007); Stim-Herndon et al., Gene 154:81-85 (1995)). Additional gene candidates include thl from Clostridium pasteurianum (Meng and Li. Cloning, Biotechnol. Lett. 28:1227-1232 (2006)) and ERG10 from S. cerevisiae (Hiser et al, J Biol Chem 269:31383-89 (1994)).

Protein
GenBank ID
GI Number
Organism

atoB
NP_416728
16130161

Escherichia coli

thlA
NP_349476.1
15896127

Clostridium acetobutylicum

thlB
NP_149242.1
15004782

Clostridium acetobutylicum

thl
ABA18857.1
75315385

Clostridium pasteurianum

ERG10
NP_015297
6325229

Saccharomyces cerevisiae

B) Acetoacetyl-CoA Reductase (Ketone Reducing).

Step B involves acetoacetyl-CoA reductase (EC#: 1.1.1.35). This second step entails the reduction of acetoacetyl-CoA to 3-hydroxybutyryl-CoA by acetoacetyl-CoA reductase. This enzyme participates in the acetyl-CoA fermentation pathway to butyrate in several species of Clostridia and has been studied in detail (Jones and Woods, Microbiol. Rev. 50:484-524 (1986)). The enzyme from Clostridium acetobutylicum, encoded by hbd, has been cloned and functionally expressed in E. coli (Youngleson et al., J. Bacteriol. 171:6800-6807 (1989)). Additionally, subunits of two fatty acid oxidation complexes in E. coli, encoded by fadB and fadJ, function as 3-hydroxyacyl-CoA dehydrogenases (Binstock and Schulz, Methods Enzymol. 71 Pt C:403-411 (1981)). Yet other genes demonstrated to reduce acetoacetyl-CoA to 3-hydroxybutyryl-CoA are phbB from Zoogloea ramigera (Ploux et al., Eur. J Biochem. 174:177-182 (1988)) and phaB from Rhodobacter sphaeroides (Alber et al., Mol. Microbiol 61:297-309 (2006)). The former gene is NADPH-dependent, its nucleotide sequence has been determined (Peoples et al., Mol. Microbiol 3:349-357 (1989)) and the gene has been expressed in E. coli. Substrate specificity studies on the gene led to the conclusion that it could accept 3-oxopropionyl-CoA as a substrate besides acetoacetyl-CoA (Ploux et al., Eur. J Biochem. 174:177-182 (1988)). Additional gene candidates include Hbd1 (C-terminal domain) and Hbd2 (N-terminal domain) in Clostridium kluyveri (Hillmer and Gottschalk, Biochim. Biophys. Acta 3334:12-23 (1974)) and HSD17B10 in Bos taurus (Wakil et al., J. Biol. Chem. 207:631-638 (1954)). The enzyme from Paracoccus denitrificans has been functionally expressed and characterized in E. coli (Yabutani et al., FEMS Microbiol Lett. 133:85-90 (1995)). A number of similar enzymes have been found in other species of Clostridia and in Metallosphaera sedula (Berg et al., Science. 318:1782-1786 (2007)). The enzyme from Candida tropicalis is a component of the peroxisomal fatty acid beta-oxidation multifunctional enzyme type 2 (MFE-2). The dehydrogenase B domain of this protein is catalytically active on acetoacetyl-CoA. The domain has been functionally expressed in E. coli, a crystal structure is available, and the catalytic mechanism is well-understood (Ylianttila et al., Biochem Biophys Res Commun 324:25-30 (2004); Ylianttila et al., J Mol Biol 358:1286-1295 (2006)).

Protein
GENBANK ID
GI NUMBER
ORGANISM

fadB
P21177.2
119811

Escherichia coli

fadJ
P77399.1
3334437

Escherichia coli

Hbd2
EDK34807.1
146348271

Clostridium kluyveri

Hbd1
EDK32512.1
146345976

Clostridium kluyveri

HSD17B10
O02691.3
3183024

Bos taurus

phbB
P23238.1
130017

Zoogloea ramigera

phaB
YP_353825.1
77464321

Rhodobacter sphaeroides

phaB
BAA08358
675524

Paracoccus denitrificans

Hbd
NP_349314.1
15895965

Clostridium acetobutylicum

Hbd
AAM14586.1
20162442

Clostridium beijerinckii

Msed_1423
YP_001191505
146304189

Metallosphaera sedula

Msed_0399
YP_001190500
146303184

Metallosphaera sedula

Msed_0389
YP_001190490
146303174

Metallosphaera sedula

Msed_1993
YP_001192057
146304741

Metallosphaera sedula

Fox2
Q02207
399508

Candida tropicalis

C) 3-Hydroxybutyrl-CoA Mutase.

Step C involves 3-hydroxybutyryl-CoA mutase (EC 5.4.99.-). In this step, 3-hydroxybutyryl-CoA is rearranged to form 2-hydroxyisobutyryl-CoA (2-HIBCoA) by 3-hydroxybutyryl-CoA mutase. This enzyme is a novel ICM-like methylmutase recently discovered and characterized in Methylibium petroleiphilum (Ratnatilleke et al., J. Biol. Chem. 274:31679-31685 (1999); Rohwerder et al., Appl. Environ. Microbiol. 72:4128-4135 (2006)). This enzyme, encoded by Mpe_B0541 in Methylibium petroleiphilum PM1, has high sequence homology to the large subunit of methylmalonyl-CoA mutase in other organisms including Rsph17029_3657 in Rhodobacter sphaeroides and Xaut_5021 in Xanthobacter autotrophicus. Changes to a single amino acid near the active site alters the substrate specificity of the enzyme (Ratnatilleke et al., supra, 1999; Rohwerder et al., supra, 2006), so directed engineering of similar enzymes at this site, such as methylmalonyl-CoA mutase or isobutryryl-CoA mutase described previously, can be used to achieve the desired reactivity.

Gene
GenBank ID
GI Number
Organism

Mpe_B0541
YP_001023546.1
124263076

Methylibium

petroleiphilum

PM1

Rsph17029_3657
YP_001045519.1
126464406

Rhodobacter

sphaeroides

Xaut_5021
YP_001409455.1
154243882

Xanthobacter

autotrophicus

Py2

D) 2-Hydroxyisobutyryl-CoA Dehydratase.

Step D involves 2-hydroxyisobutyryl-CoA dehydratase. The dehydration of 2-hydroxyacyl-CoA such as 2-hydroxyisobutyryl-CoA can be catalyzed by a special class of oxygen-sensitive enzymes that dehydrate 2-hydroxyacyl-CoA derivatives via a radical-mechanism (Buckel and Golding, Annu. Rev. Microbiol. 60:27-49 (2006); Buckel et al., Curr. Opin. Chem. Biol. 8:462-467 (2004); Buckel et al., Biol. Chem. 386:951-959 (2005); Kim et al., FEBS J. 272:550-561 (2005); Kim et al., FEMS Microbiol. Rev. 28:455-468 (2004); Zhang et al., Microbiology 145 (Pt 9):2323-2334 (1999)). One example of such an enzyme is the lactyl-CoA dehydratase from Clostridium propionicum, which catalyzes the dehydration of lactoyl-CoA to form acryl-CoA (Kuchta and Abeles, J. Biol. Chem. 260:13181-13189 (1985); Hofmeister and Buckel, Eur. J. Biochem. 206:547-552 (1992)). An additional example is 2-hydroxyglutaryl-CoA dehydratase encoded by hgdABC from Acidaminococcus fermentans (Muëller and Buckel, Eur. J. Biochem. 230:698-704 (1995); Schweiger et al., Eur. J. Biochem. 169:441-448 (1987)). Yet another example is the 2-hydroxyisocaproyl-CoA dehydratase from Clostridium difficile catalyzed by hadBC and activated by hadI (Darley et al., FEBS J. 272:550-61 (2005)). The corresponding sequences for A. fermentans and C. difficile can be found as listed below. The sequence of the complete C. propionicium lactoyl-CoA dehydratase is not yet listed in publicly available databases. However, the sequence of the beta-subunit corresponds to the GenBank accession number AJ276553 (Selmer et al, Eur J Biochem, 269:372-80 (2002)).

GenBank

Gene
Accession No.
GI No.
Organism

hgdA
P11569
296439332

Acidaminococcus fermentans

hgdB
P11570
296439333

Acidaminococcus fermentans

hgdC
P11568
2506909

Acidaminococcus fermentans

hadB
YP_001086863
126697966

Clostridium difficile

hadC
YP_001086864
126697967

Clostridium difficile

hadI
YP_001086862
126697965

Clostridium difficile

lcdB
AJ276553
7242547

Clostridium propionicum

E) Methacrylyl-CoA Synthetase, Hydrolase, or Transferase, and F) 2-Hydroxyisobutyryl-CoA Synthetase, Hydrolase, or Transferase.

Steps E and F involve a transferase (EC 2.8.3.-), hydrolase (EC 3.1.2.-), or synthetase (EC 6.2.1.-) with activity on a methacrylic acid or 2-hydroxyisobutyric acid, respectively. Direct conversion of methacrylyl-CoA to MAA or 2-hydroxyisobutyryl-CoA to 2-hydrioxyisobutyrate can be accomplished by a CoA transferase, synthetase or hydrolase. Pathway energetics are most favorable if a CoA transferase or a CoA synthetase is employed to accomplish this transformation. In the transferase family, the enzyme acyl-CoA:acetate-CoA transferase, also known as acetate-CoA transferase, is a suitable candidate to catalyze the desired 2-hydroxyisobutyryl-CoA or methacryl-CoA transferase activity due to its broad substrate specificity that includes branched acyl-CoA substrates (Matthies and Schink, Appl. Environ. Microbiol. 58:1435-1439 (1992); Vanderwinkel et al., Biochem. Biophys. Res. Commun. 33:902-908 (1968)). ADP-forming acetyl-CoA synthetase (ACD) is a promising enzyme in the CoA synthetase family operating on structurally similar branched chain compounds (Brasen and Schonheit, Arch. Microbiol. 182:277-287 (2004); Musfeldt and Schonheit, J. Bacteriol. 184:636-644 (2002)). In the CoA-hydrolase family, the enzyme 3-hydroxyisobutyryl-CoA hydrolase has been shown to operate on a variety of branched chain acyl-CoA substrates including 3-hydroxyisobutyryl-CoA, methylmalonyl-CoA, and 3-hydroxy-2-methylbutanoyl-CoA (Hawes et al., Methods Enzymol. 324:218-228 (2000); Hawes et al., J. Biol. Chem. 271:26430-26434 (1996); Shimomura et al., J. Biol. Chem. 269:14248-14253 (1994)). Additional exemplary gene candidates for CoA transferases, synthetases, and hydrolases are discussed elsewhere above.

Example XV
Attenuation or Disruption of Endogenous Enzymes

This example provides endogenous enzyme targets for attenuation or disruption that can be used for enhancing carbon flux through methanol dehydrogenase and formaldehyde assimilation pathways.

DHA Kinase

Methylotrophic yeasts typically utilize a cytosolic DHA kinase to catalyze the ATP-dependent activation of DHA to DHAP. DHAP together with G3P is combined to form fructose-1,6-bisphosphate (FBP) by FBP aldolase. FBP is then hydrolyzed to F6P by fructose bisphosphatase. The net conversion of DHA and G3P to F6P by this route is energetically costly (1 ATP) in comparison to the F6P aldolase route, described above and shown in FIG. 1. DHA kinase also competes with F6P aldolase for the DHA substrate. Attenuation of endogenous DHA kinase activity will thus improve the energetics of formaldehyde assimilation pathways, and also increase the intracellular availability of DHA for DHA synthase. DHA kinases of Saccharomyces cerevisiae, encoded by DAK1 and DAK2, enable the organism to maintain low intracellular levels of DHA (Molin et al, J Biol Chem 278:1415-23 (2003)). In methylotrophic yeasts DHA kinase is essential for growth on methanol (Luers et al, Yeast 14:759-71 (1998)). The DHA kinase enzymes of Hansenula polymorpha and Pichia pastoris are encoded by DAK (van der Klei et al, Curr Genet 34:1-11 (1998); Luers et al, supra). DAK enzymes in other organisms can be identified by sequence similarity to known enzymes.

Protein
GenBank ID
GI Number
Organism

DAK1
NP_013641.1
6323570

Saccharomyces cerevisiae

DAK2
NP_116602.1
14318466

Saccharomyces cerevisiae

DAK
AAC27705.1
3171001

Hansenula polymorpha

DAK
AAC39490.1
3287486

Pichia pastoris

DAK2
XP_505199.1
50555582

Yarrowia lipolytica

Methanol Oxidase

Attenuation of redox-inefficient endogenous methanol oxidizing enzymes, combined with increased expression of a cytosolic NADH-dependent methanol dehydrogenase, will enable redox-efficient oxidation of methanol to formaldehyde in the cytosol. Methanol oxidase, also called alcohol oxidase (EC 1.1.3.13), catalyzes the oxygen-dependent oxidation of methanol to formaldehyde and hydrogen peroxide. In eukaryotic organisms, alcohol oxidase is localized in the peroxisome. Exemplary methanol oxidase enzymes are encoded by AOD of Candida boidinii (Sakai and Tani, Gene 114:67-73 (1992)); and AOX of H. polymorpha, P. methanolica and P. pastoris (Ledeboer et al, Nucl Ac Res 13:3063-82 (1985); Koutz et al, Yeast 5:167-77 (1989); Nakagawa et al, Yeast 15:1223-1230 (1999)).

Protein
GenBank ID
GI Number
Organism

AOX2
AAF02495.1
6049184

Pichia methanolica

AOX1
AAF02494.1
6049182

Pichia methanolica

AOX1
AAB57849.1
2104961

Pichia pastoris

AOX2
AAB57850.1
2104963

Pichia pastoris

AOX
P04841.1
113652

Hansenula polymorpha

AOD1
Q00922.1
231528

Candida boidinii

AOX1
AAQ99151.1
37694459

Ogataea pini

PQQ-Dependent Methanol Dehydrogenase

PQQ-dependent methanol dehydrogenase from M. extorquens (mxaIF) uses cytochrome as an electron carrier (Nunn et al, Nucl Acid Res 16:7722 (1988)). Methanol dehydrogenase enzymes of methanotrophs such as Methylococcus capsulatis function in a complex with methane monooxygenase (MMO) (Myronova et al, Biochem 45:11905-14 (2006)). Note that of accessory proteins, cytochrome CL and PQQ biosynthesis enzymes are needed for active methanol dehydrogenase. Attenuation of one or more of these required accessory proteins, or retargeting the enzyme to a different cellular compartment, would also have the effect of attenuating PQQ-dependent methanol dehydrogenase activity.

Protein
GenBank ID
GI Number
Organism

MCA0299
YP_112833.1
53802410

Methylococcus capsulatis

MCA0782
YP_113284.1
53804880

Methylococcus capsulatis

mxaI
YP_002965443.1
240140963

Methylobacterium

extorquens

mxaF
YP_002965446.1
240140966

Methylobacterium

extorquens

DHA Synthase and Other Competing Formaldehyde Assimilation and Dissimilation Pathways

Carbon-efficient formaldehyde assimilation can be improved by attenuation of competing formaldehyde assimilation and dissimilation pathways. Exemplary competing assimilation pathways in eukaryotic organisms include the peroxisomal dissimilation of formaldehyde by DHA synthase, and the DHA kinase pathway for converting DHA to F6P, both described herein. Exemplary competing endogenous dissimilation pathways include one or more of the enzymes shown in FIG. 1.

Methylotrophic yeasts normally target selected methanol assimilation and dissimilation enzymes to peroxisomes during growth on methanol, including methanol oxidase, DHA synthase and S-(hydroxymethyl)-glutathione synthase (see review by Yurimoto et al, supra). The peroxisomal targeting mechanism comprises an interaction between the peroxisomal targeting sequence and its corresponding peroxisomal receptor (Lametschwandtner et al, J Biol Chem 273:33635-43 (1998)). Peroxisomal methanol pathway enzymes in methylotrophic organisms contain a PTS1 targeting sequence which binds to a peroxisomal receptor, such as Pex5p in Candida boidinii (Horiguchi et al, J Bacteriol 183:6372-83 (2001)). Disruption of the PTS1 targeting sequence, the Pex5p receptor and/or genes involved in peroxisomal biogenesis would enable cytosolic expression of DHA synthase, S-(hydroxymethyl)-glutathione synthase or other methanol-inducible peroxisomal enzymes. PTS1 targeting sequences of methylotrophic yeast are known in the art (Horiguchi et al, supra). Identification of peroxisomal targeting sequences of unknown enzymes can be predicted using bioinformatic methods (eg. Neuberger et al, J Mol Biol 328:581-92 (2003))).

Example XVI
Methanol Assimilation Via Methanol Dehydrogenase and the Ribulose Monophosphate Pathway

This example shows that co-expression of an active enzymes of the Ribulose Monophosphate (RuMP) pathway can effectively assimilate methanol derived carbon.

An experimental system was designed to test the ability of a MeDH in conjunction with the enzymes H6P synthase (HPS) and 6-phospho-3-hexuloisomerase (PHI) of the RuMP pathway to assimilate methanol carbon into the glycolytic pathway and the TCA cycle. Escherichia coli strain ECh-7150 (ΔlacIA, ΔpflB, ΔptsI, ΔPpckA(pckA), ΔPglk(glk), glk::glfB, ΔhycE, ΔfrmR, ΔfrmA, ΔfrmB) was constructed to remove the glutathione-dependent formaldehyde detoxification capability encoded by the FrmA and FrmB enzyme. This strain was then transformed with plasmid pZA23S variants that either contained or lacked gene 2616A encoding a fusion of the HPS and PHI enzymes. These two transformed strains were then each transformed with pZS*13S variants that contained gene 2315L (encoding an active MeDH), or gene 2315 RIP2 (encoding a catalytically inactive MeDH), or no gene insertion. Genes 2315 and 2616 are internal nomenclatures for NAD-dependent methanol dehydrogenase from Bacillus methanolicus MGA3 and 2616 is a fused phs-hpi constructs as described in Orita et al. (2007) Appl Microbiol Biotechnol 76:439-45.

The six resulting strains were aerobically cultured in quadruplicate, in 5 ml minimal medium containing 1% arabinose and 0.6 M 13C-methanol as well as 100 ug/ml carbenicillin and 25 μg/ml kanamycin to maintain selection of the plasmids, and 1 mM IPTG to induce expression of the methanol dehydrogenase and HPS-PHI fusion enzymes. After 18 hours incubation at 37° C., the cell density was measured spectrophotometrically at 600 nM wavelength and a clarified sample of each culture medium was submitted for analysis to detect evidence of incorporation of the labeled methanol carbon into TCA-cycle derived metabolites. The label can be further enriched by deleting the gene araD that competes with ribulose-5-phosphate.

¹³C carbon derived from labeled methanol provided in the experiment was found to be significantly enriched in the metabolites pyruvate, lactate, succinate, fumarate, malate, glutamate and citrate, but only in the strain expressing both catalytically active MeDH 2315L and the HPS-PHI fusion 2616A together (data not shown). Moreover, this strain grew significantly better than the strain expressing catalytically active MeDH but lacking expression of the HPS-PHI fusion (data not shown), suggesting that the HPS-PHI enzyme is capable of reducing growth inhibitory levels of formaldehyde that cannot be detoxified by other means in this strain background. These results show that co-expression of an active MeDH and the enzymes of the RuMP pathway can effectively assimilate methanol derived carbon and channel it into TCA-cycle derived products.

Example XVII

The following example describes the enzymes and the gene candidates required for production of 2,4-pentadienoate and butadiene as shown in FIG. 11.

Step A, FIG. 11: Acetaldehyde Dehydrogenase

The reduction of acetyl-CoA to acetaldehyde can be catalyzed by NAD(P)+-dependent acetaldehyde dehydrogenase (EC 1.2.1.10). Acylating acetaldehyde dehydrogenases of E. coli are encoded by adhE and mhpF (Ferrandez et al, J Bacteriol 179:2573-81 (1997)). The Pseudomonas sp. CF600 enzyme, encoded by dmpF, participates in meta-cleavage pathways and forms a complex with 4-hydroxy-2-oxovalerate aldolase (Shingler et al, J Bacteriol 174:711-24 (1992)). BphJ, a nonphosphorylating acylating aldehyde dehydrogenase, catalyzes the conversion of aldehydes to form acyl-coenzyme A in the presence of NAD(+) and coenzyme A (CoA) (Baker et al., Biochemistry, 2012 Jun. 5; 51(22):4558-67. Epub 2012 May 21). Solventogenic organisms such as Clostridium acetobutylicum encode bifunctional enzymes with alcohol dehydrogenase and acetaldehyde dehydrogenase activities. The bifunctional C. acetobutylicum enzymes are encoded by bdh I and adhE2 (Walter, et al., J. Bacteriol. 174:7149-7158 (1992); Fontaine et al., J. Bacteriol. 184:821-830 (2002)). Yet another candidate for acylating acetaldehyde dehydrogenase is the ald gene from Clostridium beijerinckii (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999). This gene is very similar to the eutE acetaldehyde dehydrogenase genes of Salmonella typhimurium and E. coli (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999).

Protein
GenBank ID
GI Number
Organism

adhE
NP_415757.1
16129202

Escherichia coli

mhpF
NP_414885.1
16128336

Escherichia coli

dmpF
CAA43226.1
45683

Pseudomonas sp. CF600

adhE2
AAK09379.1
12958626

Clostridium

acetobutylicum

bdh I
NP_349892.1
15896543

Clostridium

acetobutylicum

Ald
AAT66436
49473535

Clostridium beijerinckii

eutE
NP_416950
16130380

Escherichia coli

eutE
AAA80209
687645

Salmonella typhimurium

bphJ
CAA54035.1
520923

Burkholderia xenovorans

LB400

Other acyl-CoA dehydrogenases that reduce an acyl-CoA to its corresponding aldehyde include fatty acyl-CoA reductase (EC 1.2.1.42, 1.2.1.50), succinyl-CoA reductase (EC 1.2.1.76), acetyl-CoA reductase, butyryl-CoA reductase and propionyl-CoA reductase (EC 1.2.1.3). Aldehyde forming acyl-CoA reductase enzymes with demonstrated activity on acyl-CoA, 3-hydroxyacyl-CoA and 3-oxoacyl-CoA substrates are known in the literature. Several acyl-CoA reductase enzymes are active on 3-hydroxyacyl-CoA substrates. For example, some butyryl-CoA reductases from Clostridial organisms, are active on 3-hydroxybutyryl-CoA and propionyl-CoA reductase of L. reuteri is active on 3-hydroxypropionyl-CoA. An enzyme for converting 3-oxoacyl-CoA substrates to their corresponding aldehydes is malonyl-CoA reductase. Enzymes in this class can be refined using evolution or enzyme engineering methods known in the art to have activity on enoyl-CoA substrates.

Exemplary fatty acyl-CoA reductases enzymes are encoded by acr1 of Acinetobacter calcoaceticus (Reiser, Journal of Bacteriology 179:2969-2975 (1997)) and Acinetobacter sp. M-1 (Ishige et al., Appl. Environ. Microbiol. 68:1192-1195 (2002)). Two gene products from Mycobacterium tuberculosis accept longer chain fatty acyl-CoA substrates of length C16-C18 (Harminder Singh, U. Central Florida (2007)). Yet another fatty acyl-CoA reductase is LuxC of Photobacterium phosphoreum (Lee et al, Biochim Biohys Acta 1388:215-22 (1997)). Enzymes with succinyl-CoA reductase activity are encoded by sucD of Clostridium kluyveri (Sohling, J. Bacteriol. 178:871-880 (1996)) and sucD of P. gingivalis (Takahashi, J. Bacteriol 182:4704-4710 (2000)). Additional succinyl-CoA reductase enzymes participate in the 3-hydroxypropionate/4-hydroxybutyrate cycle of thermophilic archaea including Metallosphaera sedula (Berg et al., Science 318:1782-1786 (2007)) and Thermoproteus neutrophilus (Ramos-Vera et al., J Bacteriol, 191:4286-4297 (2009)). The M. sedula enzyme, encoded by Msed_0709, is strictly NADPH-dependent and also has malonyl-CoA reductase activity. The T. neutrophilus enzyme is active with both NADPH and NADH. The enzyme acylating acetaldehyde dehydrogenase in Pseudomonas sp, encoded by bphG, is yet another as it has been demonstrated to oxidize and acylate acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde and formaldehyde (Powlowski, J. Bacteriol. 175:377-385 (1993)). In addition to reducing acetyl-CoA to ethanol, the enzyme encoded by adhE in Leuconostoc mesenteroides has been shown to oxidize the branched chain compound isobutyraldehyde to isobutyryl-CoA (Kazahaya, J. Gen. Appl. Microbiol. 18:43-55 (1972); and Koo et al., Biotechnol Lett. 27:505-510 (2005)). Butyraldehyde dehydrogenase catalyzes a similar reaction, conversion of butyryl-CoA to butyraldehyde, in solventogenic organisms such as Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci Biotechnol Biochem., 71:58-68 (2007)). Exemplary propionyl-CoA reductase enzymes include pduP of Salmonella typhimurium LT2 (Leal, Arch. Microbiol. 180:353-361 (2003)) and eutE from E. coli (Skraly, WO Patent No. 2004/024876). The propionyl-CoA reductase of Salmonella typhimurium LT2, which naturally converts propionyl-CoA to propionaldehyde, also catalyzes the reduction of 5-hydroxyvaleryl-CoA to 5-hydroxypentanal (WO 2010/068953A2). The propionaldehyde dehydrogenase of Lactobacillus reuteri, PduP, has a broad substrate range that includes butyraldehyde, valeraldehyde and 3-hydroxypropionaldehyde (Luo et al, Appl Microbiol Biotech, 89: 697-703 (2011)). Additionally, some acyl-ACP reductase enzymes such as the orf1594 gene product of Synechococcus elongatus PCC7942 also exhibit aldehyde-forming acyl-CoA reductase activity (Schirmer et al, Science, 329: 559-62 (2010)).

sProtein
GenBank ID
GI Number
Organism

acr1
YP_047869.1
50086359

Acinetobacter calcoaceticus

acr1
AAC45217
1684886

Acinetobacter baylyi

acr1
BAB85476.1
18857901

Acinetobacter sp. Strain M-1

Rv1543
NP_216059.1
15608681

Mycobacterium tuberculosis

Rv3391
NP_217908.1
15610527

Mycobacterium tuberculosis

LUXC
AAT00788.1
46561111

Photobacterium phosphoreum

MSED_0709
YP_001190808.1
146303492

Metallosphaera sedula

Tneu_0421
ACB39369.1
170934108

Thermoproteus neutrophilus

sucD
P38947.1
172046062

Clostridium kluyveri

sucD
NP_904963.1
34540484

Porphyromonas gingivalis

bphG
BAA03892.1
425213

Pseudomonas sp

adhE
AAV66076.1
55818563

Leuconostoc mesenteroides

Bld
AAP42563.1
31075383

Clostridium

saccharoperbutylacetonicum

pduP
NP_460996
16765381

Salmonella typhimurium LT2

eutE
NP_416950
16130380

Escherichia coli

pduP
CCC03595.1
337728491

Lactobacillus reuteri

Additionally, some acyl-ACP reductase enzymes such as the orf1594 gene product of Synechococcus elongatus PCC7942 also exhibit aldehyde-forming acyl-CoA reductase activity (Schirmer et al, Science, 329: 559-62 (2010)). The S. elongates PCC7942 acyl-ACP reductase is coexpressed with an aldehyde decarbonylase in an operon that appears to be conserved in a majority of cyanobacterial organisms. This enzyme, expressed in E. coli together with the aldehyde decarbonylase, conferred the ability to produce alkanes. The P. marinus AAR was also cloned into E. coli and, together with a decarbonylase, demonstrated production of alkanes (see, e.g., US Application 2011/0207203).

Gene
GenBank ID
GI Number
Organism

orf1594
YP_400611.1
81300403

Synechococcus elongatus

PCC7942

PMT9312_0533
YP_397030.1
78778918

Prochlorococcus marinus MIT

9312

syc0051_d
YP_170761.1
56750060

Synechococcus elongatus PCC

6301

Ava_2534
YP_323044.1
75908748

Anabaena variabilis ATCC

29413

alr5284
NP_489324.1
17232776

Nostoc sp. PCC 7120

Aazo_3370
YP_003722151.1
298491974

Nostoc azollae

Cyan7425_0399
YP_002481152.1
220905841

Cyanothece sp. PCC 7425

N9414_21225
ZP_01628095.1
119508943

Nodularia spumigena

CCY9414

L8106_07064
ZP_01619574.1
119485189

Lyngbya sp. PCC 8106

An additional enzyme type that converts an acyl-CoA to its corresponding aldehyde is malonyl-CoA reductase which transforms malonyl-CoA to malonic semialdehyde. Malonyl-CoA reductase is a key enzyme in autotrophic carbon fixation via the 3-hydroxypropionate cycle in thermoacidophilic archaeal bacteria (Berg, Science 318:1782-1786 (2007); and Thauer, Science 318:1732-1733 (2007)). The enzyme utilizes NADPH as a cofactor and has been characterized in Metallosphaera and Sulfolobus sp. (Alber et al., J. Bacteriol. 188:8551-8559 (2006); and Hugler, J. Bacteriol. 184:2404-2410 (2002)). The enzyme is encoded by Msed_0709 in Metallosphaera sedula (Alber et al., J. Bacteriol. 188:8551-8559 (2006); and Berg, Science 318:1782-1786 (2007)). A gene encoding a malonyl-CoA reductase from Sulfolobus tokodaii was cloned and heterologously expressed in E. coli (Alber et al., J. Bacteriol 188:8551-8559 (2006). This enzyme has also been shown to catalyze the conversion of methylmalonyl-CoA to its corresponding aldehyde (WO2007141208 (2007)). Although the aldehyde dehydrogenase functionality of these enzymes is similar to the bifunctional dehydrogenase from Chloroflexus aurantiacus, there is little sequence similarity. Both malonyl-CoA reductase enzyme candidates have high sequence similarity to aspartate-semialdehyde dehydrogenase, an enzyme catalyzing the reduction and concurrent dephosphorylation of aspartyl-4-phosphate to aspartate semialdehyde. Additional gene candidates can be found by sequence homology to proteins in other organisms including Sulfolobus solfataricus and Sulfolobus acidocaldarius and have been listed below. Yet another candidate for CoA-acylating aldehyde dehydrogenase is the ald gene from Clostridium beijerinckii (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999). This enzyme has been reported to reduce acetyl-CoA and butyryl-CoA to their corresponding aldehydes. This gene is very similar to eutE that encodes acetaldehyde dehydrogenase of Salmonella typhimurium and E. coli (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999).

Gene
GenBank ID
GI Number
Organism

Msed_0709
YP_001190808.1
146303492

Metallosphaera sedula

mcr
NP_378167.1
15922498

Sulfolobus tokodaii

asd-2
NP_343563.1
15898958

Sulfolobus solfataricus

Saci_2370
YP_256941.1
70608071

Sulfolobus

acidocaldarius

Step B, FIG. 11: 4-hydroxy 2-oxovalerate Aldolase

The condensation of pyruvate and acetaldehyde to 4-hydroxy-2-oxovalerate is catalyzed by 4-hydroxy-2-oxovalerate aldolase (EC 4.1.3.39). This enzyme participates in pathways for the degradation of phenols, cresols and catechols. The E. coli enzyme, encoded by mhpE, is highly specific for acetaldehyde as an acceptor but accepts the alternate substrates 2-ketobutyrate or phenylpyruvate as donors (Pollard et al., Appl Environ Microbiol 64:4093-4094 (1998)). Similar enzymes are encoded by the cmtG and todH genes of Pseudomonas putida (Lau et al., Gene 146:7-13 (1994); Eaton, J Bacteriol. 178:1351-1362 (1996)). In Pseudomonas CF600, this enzyme is part of a bifunctional aldolase-dehydrogenase heterodimer encoded by dmpFG (Manjasetty et al., Acta Crystallogr. D. Biol Crystallogr. 57:582-585 (2001)). The dehydrogenase functionality interconverts acetaldehyde and acetyl-CoA, providing the advantage of reduced cellular concentrations of acetaldehyde, toxic to some cells. It has been shown recently that substrate channeling can occur within this enzyme in the presence of NAD and residues that could play an important role in channeling acetaldehyde into the DmpF site were also identified.

Gene
GenBank ID
GI Number
Organism

mhpE
AAC73455.1
1786548

Escherichia coli

cmtG
AAB62295.1
1263190

Pseudomonas putida

todH
AAA61944.1
485740

Pseudomonas putida

dmpG
CAA43227.1
45684

Pseudomonas sp. CF600

dmpF
CAA43226.1
45683

Pseudomonas sp. CF600

bphI
CAA54036.1
520924

Burkholderia xenovorans LB400

Step C, FIG. 11: 4-hydroxy 2-oxovalerate Dehydratase

The dehydration of 4-hydroxy-2-oxovalerate to 2-oxopentenoate is catalyzed by 4-hydroxy-2-oxovalerate hydratase (EC 4.2.1.80). 4-Hydroxy-2-oxovalerate hydratase participates in aromatic degradation pathways and is typically co-transcribed with a gene encoding an enzyme with 4-hydroxy-2-oxovalerate aldolase activity. Exemplary gene products are encoded by mhpD of E. coli (Ferrandez et al., J Bacteriol. 179:2573-2581 (1997); Pollard et al., Eur J Biochem. 251:98-106 (1998)), todG and cmtF of Pseudomonas putida (Lau et al., Gene 146:7-13 (1994); Eaton, J Bacteriol. 178:1351-1362 (1996)), cnbE of Comamonas sp. CNB-1 (Ma et al., Appl Environ Microbiol 73:4477-4483 (2007)) and mhpD of Burkholderia xenovorans (Wang et al., FEBS J 272:966-974 (2005)). A closely related enzyme, 2-oxohepta-4-ene-1,7-dioate hydratase, participates in 4-hydroxyphenylacetic acid degradation, where it converts 2-oxo-hept-4-ene-1,7-dioate (OHED) to 2-oxo-4-hydroxy-hepta-1,7-dioate using magnesium as a cofactor (Burks et al., J. Am. Chem. Soc. 120: (1998)). OHED hydratase enzyme candidates have been identified and characterized in E. coli C (Roper et al., Gene 156:47-51 (1995); Izumi et al., J Mo. Biol. 370:899-911 (2007)) and E. coli W (Prieto et al., J Bacteriol. 178:111-120 (1996)). Sequence comparison reveals homologs in a wide range of bacteria, plants and animals. Enzymes with highly similar sequences are contained in Klebsiella pneumonia (91% identity, eval=2e−138) and Salmonella enterica (91% identity, eval=4e−138), among others.

Gene
GenBank ID
GI Number
Organism

mhpD
AAC73453.2
87081722

Escherichia coli

cmtF
AAB62293.1
1263188

Pseudomonas putida

todG
AAA61942.1
485738

Pseudomonas putida

cnbE
YP_001967714.1
190572008

Comamonas sp. CNB-1

mhpD
Q13VU0
123358582

Burkholderia xenovorans

hpcG
CAA57202.1
556840

Escherichia coli C

hpaH
CAA86044.1
757830

Escherichia coli W

hpaH
ABR80130.1
150958100

Klebsiella pneumonia

Sari_01896
ABX21779.1
160865156

Salmonella enteric

2-(Hydroxymethyl)glutarate dehydratase is a [4Fe-4S]-containing enzyme that dehydrates 2-(hydroxymethyl)glutarate to 2-methylene-glutarate, studied for its role in nicontinate catabolism in Eubacterium barkeri (formerly Clostridium barkeri) (Alhapel et al., Proc Natl Acad Sci 103:12341-6 (2006)). Similar enzymes with high sequence homology are found in Bacteroides capillosus, Anaerotruncus colihominis, and Natranaerobius thermophilius. These enzymes are homologous to the alpha and beta subunits of [4Fe-4S]-containing bacterial serine dehydratases (e.g., E. coli enzymes encoded by tdcG, sdhB, and sdaA). An enzyme with similar functionality in E. barkeri is dimethylmaleate hydratase, a reversible Fe²⁺-dependent and oxygen-sensitive enzyme in the aconitase family that hydrates dimethylmaeate to form (2R,3S)-2,3-dimethylmalate. This enzyme is encoded by dmdAB (Alhapel et al., Proc Natl Acad Sci USA 103:12341-6 (2006); Kollmann-Koch et al., Hoppe Seylers. Z. Physiol Chem. 365:847-857 (1984)).

Protein
GenBank ID
GI Number
Organism

hmd
ABC88407.1
86278275

Eubacterium

barkeri

BACCAP_02294
ZP_02036683.1
154498305

Bacteroides

capillosus

ANACOL_02527
ZP_02443222.1
167771169

Anaerotruncus

colihominis

NtherDRAFT_2368
ZP_02852366.1
169192667

Natranaerobius

thermophilus

dmdA
ABC88408
86278276

Eubacterium

barkeri

dmdB
ABC88409
86278277

Eubacterium

barkeri

Step D, FIG. 11: 2-oxopentenoate Reductase

The reduction of 2-oxopentenoate to 2-hydroxypentenoate is carried out by an alcohol dehydrogenase that reduces a ketone group. Several exemplary alcohol dehydrogenases can catalyze this transformation. Two such enzymes from E. coli are encoded by malate dehydrogenase (mdh) and lactate dehydrogenase (ldhA). In addition, lactate dehydrogenase from Ralstonia eutropha has been shown to demonstrate high activities on 2-ketoacids of various chain lengths including lactate, 2-oxobutyrate, 2-oxopentanoate and 2-oxoglutarate (Steinbuchel et al., Eur. J. Biochem. 130:329-334 (1983)). Conversion of alpha-ketoadipate into alpha-hydroxyadipate is catalyzed by 2-ketoadipate reductase, an enzyme found in rat and in human placenta (Suda et al., Arch. Biochem. Biophys. 176:610-620 (1976); Suda et al., Biochem. Biophys. Res. Commun. 77:586-591 (1977)). An additional candidate oxidoreductase is the mitochondrial 3-hydroxybutyrate dehydrogenase (bdh) from the human heart which has been cloned and characterized (Marks et al., J. Biol. Chem. 267:15459-15463 (1992)). Alcohol dehydrogenase enzymes of C. beijerinckii (Ismaiel et al., J. Bacteriol. 175:5097-5105 (1993)) and T. brockii (Lamed et al., Biochem. J. 195:183-190 (1981); Peretz et al., Biochemistry. 28:6549-6555 (1989)) convert acetone to isopropanol. Methyl ethyl ketone reductase catalyzes the reduction of MEK to 2-butanol. Exemplary MEK reductase enzymes can be found in Rhodococcus ruber (Kosjek et al., Biotechnol Bioeng. 86:55-62 (2004)) and Pyrococcus furiosus (van der et al., Eur. J. Biochem. 268:3062-3068 (2001)).

Gene
GenBank ID
GI Number
Organism

Mdh
AAC76268.1
1789632

Escherichia coli

ldhA
NP_415898.1
16129341

Escherichia coli

Ldh
YP_725182.1
113866693

Ralstonia eutropha

Bdh
AAA58352.1
177198

Homo sapiens

Adh
AAA23199.2
60592974

Clostridium beijerinckii NRRL

B593

Adh
P14941.1
113443

Thermoanaerobacter brockii

HTD4

Sadh
CAD36475
21615553

Rhodococcus ruber

adhA
AAC25556
3288810

Pyrococcus furiosus

Step E, FIG. 11: 2-hydroxypentenoate Dehydratase

Enzyme candidates for the dehydration of 2-hydroxypentenoate (FIG. 1, Step E) include fumarase (EC 4.2.1.2), citramalate hydratase (EC 4.2.1.34) and dimethylmaleate hydratase (EC 4.2.1.85). Fumarases naturally catalyze the reversible dehydration of malate to fumarate. Although the ability of fumarase to react with 2-hydroxypentenoate as substrates has not been described in the literature, a wealth of structural information is available for this enzyme and other researchers have successfully engineered the enzyme to alter activity, inhibition and localization (Weaver, Acta Crystallogr D Biol Crystallogr, 61:1395-1401 (2005)). E. coli has three fumarases: FumA, FumB, and FumC that are regulated by growth conditions. FumB is oxygen sensitive and only active under anaerobic conditions. FumA is active under microanaerobic conditions, and FumC is the only active enzyme in aerobic growth (Tseng et al., J Bacteriol, 183:461-467 (2001); Woods et al., 954:14-26 (1988); Guest et al., J Gen Microbiol 131:2971-2984 (1985)). Additional enzyme candidates are found in Campylobacter jejuni (Smith et al., Int. J Biochem. Cell Biol 31:961-975 (1999)), Thermus thermophilus (Mizobata et al., Arch. Biochem. Biophys. 355:49-55 (1998)) and Rattus norvegicus (Kobayashi et al., J Biochem, 89:1923-1931 (1981)). Similar enzymes with high sequence homology include fum1 from Arabidopsis thaliana and fumC from Corynebacterium glutamicum. The mmcBC fumarase from Pelotomaculum thermopropionicum is another class of fumarase with two subunits (Shimoyama et al., FEMS Microbiol Lett, 270:207-213 (2007)). Citramalate hydrolyase naturally dehydrates 2-methylmalate to mesaconate. This enzyme has been studied in Methanocaldococcus jannaschii in the context of the pyruvate pathway to 2-oxobutanoate, where it has been shown to have a broad substrate specificity (Drevland et al., J Bacteriol. 189:4391-4400 (2007)). This enzyme activity was also detected in Clostridium tetanomorphum, Morganella morganii, Citrobacter amalonaticus where it is thought to participate in glutamate degradation (Kato et al., Arch. Microbiol 168:457-463 (1997)). The M. jannaschii protein sequence does not bear significant homology to genes in these organisms. Dimethylmaleate hydratase is a reversible Fe²⁺-dependent and oxygen-sensitive enzyme in the aconitase family that hydrates dimethylmaeate to form (2R,3S)-2,3-dimethylmalate. This enzyme is encoded by dmdAB in Eubacterium barkeri (Alhapel et al., supra; Kollmann-Koch et al., Hoppe Seylers. Z. Physiol Chem. 365:847-857 (1984)).

Gene
GenBank ID
GI Number
Organism

fumA
NP_416129.1
16129570

Escherichia coli

fumB
NP_418546.1
16131948

Escherichia coli

fumC
NP_416128.1
16129569

Escherichia coli

fumC
O69294
9789756

Campylobacter jejuni

fumC
P84127
75427690

Thermus thermophilus

fumH
P14408
120605

Rattus norvegicus

fum1
P93033
39931311

Arabidopsis thaliana

fumC
Q8NRN8
39931596

Corynebacterium glutamicum

mmcB
YP_001211906
147677691

Pelotomaculum

thermopropionicum

mmcC
YP_001211907
147677692

Pelotomaculum

thermopropionicum

leuD
Q58673.1
3122345

Methanocaldococcus

jannaschii

dmdA
ABC88408
86278276

Eubacterium barkeri

dmdB
ABC88409.1
86278277

Eubacterium barkeri

Oleate hydratases catalyze the reversible hydration of non-activated alkenes to their corresponding alcohols. These enzymes represent additional suitable candidates as suggested in WO2011076691. Oleate hydratases from Elizabethkingia meningoseptica and Streptococcus pyogenes have been characterized (WO 2008/119735). Examples include the following proteins.

Protein
GenBank ID
GI Number
Organism

OhyA
ACT54545.1
254031735

Elizabethkingia

meningoseptica

HMPREF0841_1446
ZP_07461147.1
306827879

Streptococcus pyogenes

ATCC 10782

P700755_13397
ZP_01252267.1
91215295

Psychroflexus torquis

ATCC 700755

RPB_2430
YP_486046.1
86749550

Rhodopseudomonas

palustris

Step F, FIG. 11: 2,4-pentadienoate Decarboxylase

The decarboxylation reactions of 2,4-pentadienoate to butadiene (step F of FIG. 1) are catalyzed by enoic acid decarboxylase enzymes. Exemplary enzymes are sorbic acid decarboxylase, aconitate decarboxylase, 4-oxalocrotonate decarboxylase and cinnamate decarboxylase. Sorbic acid decarboxylase converts sorbic acid to 1,3-pentadiene. Sorbic acid decarboxylation by Aspergillus niger requires three genes: padA1, ohbA1, and sdrA (Plumridge et al. Fung. Genet. Bio, 47:683-692 (2010). PadA1 is annotated as a phenylacrylic acid decarboxylase, ohbA1 is a putative 4-hydroxybenzoic acid decarboxylase, and sdrA is a sorbic acid decarboxylase regulator. Additional species have also been shown to decarboxylate sorbic acid including several fungal and yeast species (Kinderlerler and Hatton, Food Addit Contam., 7(5):657-69 (1990); Casas et al., Int J Food Micro., 94(1):93-96 (2004); Pinches and Apps, Int. J. Food Microbiol. 116: 182-185 (2007)). For example, Aspergillus oryzae and Neosartorya fischeri have been shown to decarboxylate sorbic acid and have close homologs to padA1, ohbA1, and sdrA.

Gene name
GenBankID
GI Number
Organism

padA1
XP_001390532.1
145235767

Aspergillus niger

ohbA1
XP_001390534.1
145235771

Aspergillus niger

sdrA
XP_001390533.1
145235769

Aspergillus niger

padA1
XP_001818651.1
169768362

Aspergillus oryzae

ohbA1
XP_001818650.1
169768360

Aspergillus oryzae

sdrA
XP_001818649.1
169768358

Aspergillus oryzae

padA1
XP_001261423.1
119482790

Neosartorya fischeri

ohbA1
XP_001261424.1
119482792

Neosartorya fischeri

sdrA
XP_001261422.1
119482788

Neosartorya fischeri

Aconitate decarboxylase (EC 4.1.1.6) catalyzes the final step in itaconate biosynthesis in a strain of Candida and also in the filamentous fungus Aspergillus terreus (Bonnarme et al. J Bacteriol. 177:3573-3578 (1995); Willke and Vorlop, Appl Microbiol. Biotechnol 56:289-295 (2001)). A cis-aconitate decarboxylase (CAD) (EC 4.1.16) has been purified and characterized from Aspergillus terreus (Dwiarti et al., J Biosci. Bioeng. 94(1): 29-33 (2002)). Recently, the gene has been cloned and functionally characterized (Kanamasa et al., Appl. Microbiol Biotechnol 80:223-229 (2008)) and (WO/2009/014437). Several close homologs of CAD are listed below (EP 2017344A1; WO 2009/014437 A1). The gene and protein sequence of CAD were reported previously (EP 2017344 A1; WO 2009/014437 A1), along with several close homologs listed in the table below.

Gene name
GenBankID
GI Number
Organism

CAD
XP_001209273
115385453

Aspergillus terreus

XP_001217495
115402837

Aspergillus terreus

XP_001209946
115386810

Aspergillus terreus

BAE66063
83775944

Aspergillus oryzae

XP_001393934
145242722

Aspergillus niger

XP_391316
46139251

Gibberella zeae

XP_001389415
145230213

Aspergillus niger

XP_001383451
126133853

Pichia stipitis

YP_891060
118473159

Mycobacterium

smegmatis

NP_961187
41408351

Mycobacterium avium

subsp. pratuberculosis

YP_880968
118466464

Mycobacterium avium

ZP_01648681
119882410

Salinispora arenicola

An additional class of decarboxylases has been characterized that catalyze the conversion of cinnamate (phenylacrylate) and substituted cinnamate derivatives to the corresponding styrene derivatives. These enzymes are common in a variety of organisms and specific genes encoding these enzymes that have been cloned and expressed in E. coli are: pad 1 from Saccharomyces cerevisae (Clausen et al., Gene 142:107-112 (1994)), pdc from Lactobacillus plantarum (Barthelmebs et al., Appl Environ Microbiol. 67:1063-1069 (2001); Qi et al., Metab Eng 9:268-276 (2007); Rodriguez et al., J. Agric. Food Chem. 56:3068-3072 (2008)), poJK (pad) from Klebsiella oxytoca (Uchiyama et al., Biosci. Biotechnol. Biochem. 72:116-123 (2008); Hashidoko et al., Biosci. Biotech. Biochem. 58:217-218 (1994)), Pedicoccus pentosaceus (Barthelmebs et al., Appl Environ Microbiol. 67:1063-1069 (2001)), and padC from Bacillus subtilis and Bacillus pumilus (Shingler et al., J. Bacteriol., 174:711-724 (1992)). A ferulic acid decarboxylase from Pseudomonas fluorescens also has been purified and characterized (Huang et al., J. Bacteriol. 176:5912-5918 (1994)). Importantly, this class of enzymes have been shown to be stable and do not require either exogenous or internally bound co-factors, thus making these enzymes ideally suitable for biotransformations (Sariaslani, Annu. Rev. Microbiol. 61:51-69 (2007)).

Protein
GenBank ID
GI Number
Organism

pad1
AAB64980.1
1165293

Saccharomyces cerevisae

ohbA1
BAG32379.1
188496963

Saccharomyces cerevisiae

pdc
AAC45282.1
1762616

Lactobacillus plantarum

pad
BAF65031.1
149941608

Klebsiella oxytoca

padC
NP_391320.1
16080493

Bacillus subtilis

pad
YP_804027.1
116492292

Pedicoccus pentosaceus

pad
CAC18719.1
11691810

Bacillus pumilus

4-Oxalocronate decarboxylase catalyzes the decarboxylation of 4-oxalocrotonate to 2-oxopentanoate. This enzyme has been isolated from numerous organisms and characterized. The decarboxylase typically functions in a complex with vinylpyruvate hydratase. Genes encoding this enzyme include dmpH and dmpE in Pseudomonas sp. (strain 600) (Shingler et al., J. Bacteriol., 174:711-724 (1992)), xylII and xylIII from Pseudomonas putida (Kato et al., Arch. Microbiol 168:457-463 (1997); Stanley et al., Biochemistry 39:3514 (2000); Lian et al., J. Am. Chem. Soc. 116:10403-10411 (1994)) and Reut_B5691 and Reut_B5692 from Ralstonia eutropha JMP134 (Hughes et al., J Bacteriol, 158:79-83 (1984)). The genes encoding the enzyme from Pseudomonas sp. (strain 600) have been cloned and expressed in E. coli (Shingler et al., J Bacteriol. 174:711-724 (1992)). The 4-oxalocrotonate decarboxylase encoded by xylI in Pseudomonas putida functions in a complex with vinylpyruvate hydratase. A recombinant form of this enzyme devoid of the hydratase activity and retaining wild type decarboxylase activity has been characterized (Stanley et al., Biochem. 39:718-26 (2000)). A similar enzyme is found in Ralstonia pickettii (formerly Pseudomonas pickettii) (Kukor et al., J Bacteriol. 173:4587-94 (1991)).

Gene
GenBank
GI Number
Organism

dmpH
CAA43228.1
45685

Pseudomonas sp. CF600

dmpE
CAA43225.1
45682

Pseudomonas sp. CF600

xylII
YP_709328.1
111116444

Pseudomonas putida

xylIII
YP_709353.1
111116469

Pseudomonas putida

Reut_B5691
YP_299880.1
73539513

Ralstonia eutropha

JMP134

Reut_B5692
YP_299881.1
73539514

Ralstonia eutropha

JMP134

xylI
P49155.1
1351446

Pseudomonas putida

tbuI
YP_002983475.1
241665116

Ralstonia pickettii

nbaG
BAC65309.1
28971626

Pseudomonas fluorescens

KU-7

Numerous characterized enzymes decarboxylate amino acids and similar compounds, including aspartate decarboxylase, lysine decarboxylase and ornithine decarboxylase. Aspartate decarboxylase (EC 4.1.1.11) decarboxylates aspartate to form beta-alanine. This enzyme participates in pantothenate biosynthesis and is encoded by gene panD in Escherichia coli (Dusch et al., Appl. Environ. Microbiol 65:1530-1539 (1999); Ramjee et al., Biochem. J 323 (Pt 3):661-669 (1997); Merkel et al., FEMS Microbiol Lett. 143:247-252 (1996); Schmitzberger et al., EMBO J 22:6193-6204 (2003)). The enzymes from Mycobacterium tuberculosis (Chopra et al., Protein Expr. Purif. 25:533-540 (2002)) and Corynebacterium glutanicum (Dusch et al., Appl. Environ. Microbiol 65:1530-1539 (1999)) have been expressed and characterized in E. coli.

Protein
GenBank ID
GI Number
Organism

panD
P0A790
67470411

Escherichia coli K12

panD
Q9X4N0
18203593

Corynebacterium glutanicum

panD
P65660.1
54041701

Mycobacterium tuberculosis

Lysine decarboxylase (EC 4.1.1.18) catalyzes the decarboxylation of lysine to cadaverine. Two isozymes of this enzyme are encoded in the E. coli genome by genes cadA and ldcC. CadA is involved in acid resistance and is subject to positive regulation by the cadC gene product (Lemonnier et al., Microbiology 144 (Pt 3):751-760 (1998)). CadC accepts hydroxylysine and S-aminoethylcysteine as alternate substrates, and 2-aminopimelate and 6-aminocaproate act as competitive inhibitors to this enzyme (Sabo et al., Biochemistry 13:662-670 (1974)). The constitutively expressed ldc gene product is less active than CadA (Lemonnier and Lane, Microbiology 144 (Pt 3):751-760 (1998)). A lysine decarboxylase analogous to CadA was recently identified in Vibrio parahaemolyticus (Tanaka et al., J Appl Microbiol 104:1283-1293 (2008)). The lysine decarboxylase from Selenomonas ruminantium, encoded by ldc, bears sequence similarity to eukaryotic ornithine decarboxylases, and accepts both L-lysine and L-ornithine as substrates (Takatsuka et al., Biosci. Biotechnol Biochem. 63:1843-1846 (1999)). Active site residues were identified and engineered to alter the substrate specificity of the enzyme (Takatsuka et al., J Bacteriol. 182:6732-6741 (2000)). Several ornithine decarboxylase enzymes (EC 4.1.1.17) also exhibit activity on lysine and other similar compounds. Such enzymes are found in Nicotiana glutinosa (Lee et al., Biochem. J 360:657-665 (2001)), Lactobacillus sp. 30a (Guirard et al., J Biol. Chem. 255:5960-5964 (1980)) and Vibrio vulnificus (Lee et al., J Biol. Chem. 282:27115-27125 (2007)). The enzymes from Lactobacillus sp. 30a (Momany et al., J Mol. Biol. 252:643-655 (1995)) and V. vulnificus have been crystallized. The V. vulnificus enzyme efficiently catalyzes lysine decarboxylation and the residues involved in substrate specificity have been elucidated (Lee et al., J Biol. Chem. 282:27115-27125 (2007)). A similar enzyme has been characterized in Trichomonas vaginalis. (Yarlett et al., Biochem. J 293 (Pt 2):487-493 (1993)).

Protein
GenBank ID
GI Number
Organism

cadA
AAA23536.1
145458

Escherichia coli

ldcC
AAC73297.1
1786384

Escherichia coli

Ldc
O50657.1
13124043

Selenomonas

ruminantium

cadA
AB124819.1
44886078

Vibrio

parahaemolyticus

AF323910.1:1 . . .
AAG45222.1
12007488

Nicotiana glutinosa

1299

odc1
P43099.2
1169251

Lactobacillus

sp. 30a

VV2_1235
NP_763142.1
27367615

Vibrio vulniflcus

Steps G and J, FIG. 11: 2-oxopentenoate Ligase and 2-hydroxypentenoate Ligase

ADP and AMP-forming CoA ligases (6.2.1) with broad substrate specificities have been described in the literature. The ADP-forming acetyl-CoA synthetase (ACD, EC 6.2.1.13) from Archaeoglobus fulgidus, encoded by AF1211, was shown to operate on a variety of linear and branched-chain substrates including isobutyrate, isopentanoate, and fumarate (Musfeldt et al., J Bacteriol. 184:636-644 (2002)). A second reversible ACD in Archaeoglobus fulgidus, encoded by AF1983, was also indicated to have a broad substrate range (Musfeldt et al., supra). The enzyme from Haloarcula marismortui, annotated as a succinyl-CoA synthetase, accepts propionate, butyrate, and branched-chain acids (isovalerate and isobutyrate) as substrates, and was shown to operate in the forward and reverse directions (Brasen et al., Arch. Microbiol 182:277-287 (2004)). The ACD encoded by PAE3250 from hyperthermophilic crenarchaeon Pyrobaculum aerophilum showed the broadest substrate range of all characterized ACDs, reacting with acetyl-CoA, isobutyryl-CoA (preferred substrate) and phenylacetyl-CoA (Brasen and Schonheit, Arch. Microbiol 182:277-287 (2004)). Directed evolution or engineering can be used to modify this enzyme to operate at the physiological temperature of the host organism. The enzymes from A. fulgidus, H. marismortui and P. aerophilum have all been cloned, functionally expressed, and characterized in E. coli (Brasen and Schonheit, Arch. Microbiol 182:277-287 (2004); Musfeldt and Schonheit, J Bacteriol. 184:636-644 (2002)). An additional enzyme is encoded by sucCD in E. coli, which naturally catalyzes the formation of succinyl-CoA from succinate with the concomitant consumption of one ATP, a reaction which is reversible in vivo (Buck et al., Biochemistry 24:6245-6252 (1985)). The acyl CoA ligase from Pseudomonas putida has been indicated to work on several aliphatic substrates including acetic, propionic, butyric, valeric, hexanoic, heptanoic, and octanoic acids and on aromatic compounds such as phenylacetic and phenoxyacetic acids (Fernandez-Valverde et al., Appl. Environ. Microbiol. 59:1149-1154 (1993)). A related enzyme, malonyl CoA synthetase (6.3.4.9) from Rhizobium leguminosarum could convert several diacids, namely, ethyl-, propyl-, allyl-, isopropyl-, dimethyl-, cyclopropyl-, cyclopropylmethylene-, cyclobutyl-, and benzyl-malonate into their corresponding monothioesters (Pohl et al., J. Am. Chem. Soc. 123:5822-5823 (2001)). Recently, a CoA dependent acetyl-CoA ligase was also identified in Propionibacterium acidipropionici ATCC 4875 (Parizzi et al., BMC Genomics. 2012; 13: 562). This enzyme is distinct from the AMP-dependent acetyl-CoA synthetase and is instead related to the ADP-forming succinyl-CoA synthetase complex (SCSC). Genes related to the SCSC (α and β subunits) complex were also found in Propionibacterium acnes KPA171202 and Microlunatus phophovorus NM-1.

The acylation of acetate to acetyl-CoA is catalyzed by enzymes with acetyl-CoA synthetase activity. Two enzymes that catalyze this reaction are AMP-forming acetyl-CoA synthetase (EC 6.2.1.1) and ADP-forming acetyl-CoA synthetase (EC 6.2.1.13). AMP-forming acetyl-CoA synthetase (ACS) is the predominant enzyme for activation of acetate to acetyl-CoA. Exemplary ACS enzymes are found in E. coli (Brown et al., J. Gen. Microbiol 102:327-336 (1977)), Ralstonia eutropha (Priefert et al., J. Bacteriol 174:6590-6599 (1992)), Methanothermobacter thermautotrophicus (Ingram-Smith et al., Archaea. 2:95-107 (2007)), Salmonella enterica (Gulick et al., Biochemistry 42:2866-2873 (2003)) and Saccharomyces cerevisiae (Jogl et al., Biochemistry, 43:1425-1431 (2004)).

Methylmalonyl-CoA synthetase from Rhodopseudomonas palustris (MatB) converts methylmalonate and malonate to methylmalonyl-CoA and malonyl-CoA, respectively. Structure-based mutagenesis of this enzyme improved CoA synthetase activity with the alternate substrates ethylmalonate and butylmalonate (Crosby et al, AEM, in press (2012)).

GenBank

Gene
Accession No.
GI No.
Organism

AF1211
NP_070039.1
11498810

Archaeoglobus

fulgidus

AF1983
NP_070807.1
11499565

Archaeoglobus

fulgidus

Scs
YP_135572.1
55377722

Haloarcula

marismortui

PAE3250
NP_560604.1
18313937

Pyrobaculum

aerophilum str. IM2

sucC
NP_415256.1
16128703

Escherichia coli

sucD
AAC73823.1
1786949

Escherichia coli

paaF
AAC24333.2
22711873

Pseudomonas

putida

matB
AAC83455.1
3982573

Rhizobium

leguminosarum

Acs
AAC77039.1
1790505

Escherichia coli

acoE
AAA21945.1
141890

Ralstonia eutropha

acs1
ABC87079.1
86169671

Methanothermobacter

thermautotrophicus

acs1
AAL23099.1
16422835

Salmonella enterica

ACS1
Q01574.2
257050994

Saccharomyces

cerevisiae

LSC1
NP_014785
6324716

Saccharomyces

cerevisiae

LSC2
NP_011760
6321683

Saccharomyces

cerevisiae

bioW
NP_390902.2
50812281

Bacillus

subtilis

bioW
CAA10043.1
3850837

Pseudomonas

mendocina

bioW
P22822.1
115012

Bacillus

sphaericus

Phl
CAJ15517.1
77019264

Penicillium

chrysogenum

phlB
ABS19624.1
152002983

Penicillium

chrysogenum

paaF
AAC24333.2
22711873

Pseudomonas putida

PACID_02150
YP_006979420.1
410864809

Propionibacterium

acidipropionici

ATCC 4875

PPA1754
AAT83483.1
50840816

Propionibacterium

acnes KPA171202

PPA1755
AAT83484.1
50840817

Propionibacterium

acnes KPA171202

Subunit alpha
YP_004571669.1
336116902

Microlunatus

phosphovorus NM-1

Subunit beta
YP_004571668.1
336116901

Microlunatus

phosphovorus NM-1

AACS
NP_084486.1
21313520

Mus musculus

AACS
NP_076417.2
31982927

Homo sapiens

4HB-CoA synthetase catalyzes the ATP-dependent conversion of 4-hydroxybutyrate to 4-hydroxybutyryl-CoA. AMP-forming 4-HB-CoA synthetase enzymes are found in organisms that assimilate carbon via the dicarboxylate/hydroxybutyrate cycle or the 3-hydroxypropionate/4-hydroxybutyrate cycle. Enzymes with this activity have been characterized in Thermoproteus neutrophilus and Metallosphaera sedula (Ramos-Vera et al, J Bacteriol 192:5329-40 (2010); Berg et al, Science 318:1782-6 (2007)). Others can be inferred by sequence homology.

Protein
GenBank ID
GI Number
Organism

Tneu_0420
ACB39368.1
170934107

Thermoproteus

neutrophilus

Caur_0002
YP_001633649.1
163845605

Chloroflexus aurantiacus

J-10-fl

Cagg_3790
YP_002465062
219850629

Chloroflexus aggregans

DSM 9485

Acs
YP_003431745
288817398

Hydrogenobacter

thermophilus TK-6

Pisl_0250
YP_929773.1
119871766

Pyrobaculum islandicum

DSM 4184

Used _1422
ABP95580.1
145702438

Metallosphaera sedula

Step I, FIG. 11: 2-oxopentenoyl-CoA Reductase

The reduction of 2-oxopentenoyl CoA to 2-hydroxypentanoyl-CoA can be accomplished by 3-oxoacyl-CoA reductase enzymes (EC 1.1.1.35) that typically convert 3-oxoacyl-CoA molecules into 3-hydroxyacyl-CoA molecules and are often involved in fatty acid beta-oxidation or phenylacetate catabolism. For example, subunits of two fatty acid oxidation complexes in E. coli, encoded by fadB and fadJ, function as 3-hydroxyacyl-CoA dehydrogenases (Binstock et al., Methods Enzymol. 71 Pt C:403-411 (1981)). Given the proximity in E. coli of paaH to other genes in the phenylacetate degradation operon (Nogales et al., Microbiology, 153:357-365 (2007)) and the fact that paaH mutants cannot grow on phenylacetate (Ismail et al., Eur. J Biochem. 270:3047-3054 (2003)), it is expected that the E. coli paaH gene also encodes a 3-hydroxyacyl-CoA dehydrogenase. Additional 3-oxoacyl-CoA enzymes include the gene products of phaC in Pseudomonas putida (Olivera et al., Proc. Natl. Acad. Sci U.S.A 95:6419-6424 (1998)) and paaC in Pseudomonas fluorescens (Di et al., Arch. Microbiol 188:117-125 (2007)). These enzymes catalyze the reversible oxidation of 3-hydroxyadipyl-CoA to 3-oxoadipyl-CoA during the catabolism of phenylacetate or styrene.

Acetoacetyl-CoA reductase participates in the acetyl-CoA fermentation pathway to butyrate in several species of Clostridia and has been studied in detail (Jones et al., Microbiol Rev. 50:484-524 (1986)). The enzyme from Clostridium acetobutylicum, encoded by hbd, has been cloned and functionally expressed in E. coli (Youngleson et al., J Bacteriol. 171:6800-6807 (1989)). Yet other genes demonstrated to reduce acetoacetyl-CoA to 3-hydroxybutyryl-CoA are phbB from Zoogloea ramigera (Ploux et al., Eur. J Biochem. 174:177-182 (1988)) and phaB from Rhodobacter sphaeroides (Alber et al., Mol. Microbiol 61:297-309 (2006)). The former gene is NADPH-dependent, its nucleotide sequence has been determined (Peoples et al., Mol. Microbiol 3:349-357 (1989)) and the gene has been expressed in E. coli. Substrate specificity studies on the gene led to the conclusion that it could accept 3-oxopropionyl-CoA as a substrate besides acetoacetyl-CoA (Ploux et al., Eur. J Biochem. 174:177-182 (1988)). Additional genes include phaB in Paracoccus denitrificans, Hbd1 (C-terminal domain) and Hbd2 (N-terminal domain) in Clostridium kluyveri (Hillmer and Gottschalk, Biochim. Biophys. Acta 3334:12-23 (1974)) and HSD17B10 in Bos taurus (Wakil et al., J Biol. Chem. 207:631-638 (1954)). The enzyme from Paracoccus denitrificans has been functionally expressed and characterized in E. coli (Yabutani et al., FEMS Microbiol Lett. 133:85-90 (1995)). A number of similar enzymes have been found in other species of Clostridia and in Metallosphaera sedula (Berg et al., Science. 318:1782-1786 (2007)). The enzyme from Candida tropicalis is a component of the peroxisomal fatty acid beta-oxidation multifunctional enzyme type 2 (MFE-2). The dehydrogenase B domain of this protein is catalytically active on acetoacetyl-CoA. The domain has been functionally expressed in E. coli, a crystal structure is available, and the catalytic mechanism is well-understood (Ylianttila et al., Biochem Biophys Res Commun 324:25-30 (2004); Ylianttila et al., J Mol Biol 358:1286-1295 (2006)). 3-Hydroxyacyl-CoA dehydrogenases that accept longer acyl-CoA substrates (eg. EC 1.1.1.35) are typically involved in beta-oxidation. An example is HSD17B10 in Bos taurus (WAKIL et al., J Biol. Chem. 207:631-638 (1954)). phbB from Cupriavidus necatar codes for a 3-hydroxyvaleryl-CoA dehydrogenase activity.

Protein
GENBANK ID
GI NUMBER
ORGANISM

fadB
P21177.2
119811

Escherichia coli

fadJ
P77399.1
3334437

Escherichia coli

paaH
NP_415913.1
16129356

Escherichia coli

Hbd2
EDK34807.1
146348271

Clostridium

kluyveri

Hbd1
EDK32512.1
146345976

Clostridium

kluyveri

phaC
NP_745425.1
26990000

Pseudomonas putida

paaC
ABF82235.1
106636095

Pseudomonas

fluorescens

HSD17B10
O02691.3
3183024

Bos Taurus

phbB
P23238.1
130017

Zoogloea ramigera

phaB
YP_353825.1
77464321

Rhodobacter

sphaeroides

phaB
BAA08358
675524

Paracoccus

denitrificans

phbB
AEI82198.1
338171145

Cupriavidus necator

Hbd
NP_349314.1
15895965

Clostridium

acetobutylicum

Hbd
AAM14586.1
20162442

Clostridium

beijerinckii

Msed_1423
YP_001191505
146304189

Metallosphaera sedula

Msed_0399
YP_001190500
146303184

Metallosphaera sedula

Msed_0389
YP_001190490
146303174

Metallosphaera sedula

Msed_1993
YP_001192057
146304741

Metallosphaera sedula

Fox2
Q02207
399508

Candida tropicalis

HSD17B10
O02691.3
3183024

Bos Taurus

Other exemplary enzymes that can carry this reaction are 2-hydroxyacid dehydrogenases. Such an enzyme. characterized from the halophilic archaeon Haloferax mediterranei catalyses a reversible stereospecific reduction of 2-ketocarboxylic acids into the corresponding D-2-hydroxycarboxylic acids. The enzyme is strictly NAD-dependent and prefers substrates with a main chain of 3-4 carbons (pyruvate and 2-oxobutanoate). Activity with 4-methyl-2-oxopentanoate is 10-fold lower. Two such enzymes from E. coli are encoded by malate dehydrogenase (mdh) and lactate dehydrogenase (ldhA). In addition, lactate dehydrogenase from Ralstonia eutropha has been shown to demonstrate high activities on 2-ketoacids of various chain lengths includings lactate, 2-oxobutyrate, 2-oxopentanoate and 2-oxoglutarate (Steinbuchel et al., Eur. J. Biochem. 130:329-334 (1983)). Conversion of alpha-ketoadipate into alpha-hydroxyadipate can be catalyzed by 2-ketoadipate reductase, an enzyme reported to be found in rat and in human placenta (Suda et al., Arch. Biochem. Biophys. 176:610-620 (1976); Suda et al., Biochem. Biophys. Res. Commun. 77:586-591 (1977)). An additional oxidoreductase is the mitochondrial 3-hydroxybutyrate dehydrogenase (bdh) from the human heart which has been cloned and characterized (Marks et al., J. Biol. Chem. 267:15459-15463 (1992)). Alcohol dehydrogenase enzymes of C. beijerinckii (Ismaiel et al., J. Bacteriol. 175:5097-5105 (1993)) and T. brockii (Lamed et al., Biochem. J. 195:183-190 (1981); Peretz et al., Biochemistry. 28:6549-6555 (1989)) convert acetone to isopropanol. Methyl ethyl ketone reductase catalyzes the reduction of MEK to 2-butanol. Exemplary MEK reductase enzymes can be found in Rhodococcus ruber (Kosjek et al., Biotechnol Bioeng. 86:55-62 (2004)) and Pyrococcus furiosus (van der et al., Eur. J. Biochem. 268:3062-3068 (2001)).

GenBank

Gene
Accession No.
GI No.
Organism

mdh
AAC76268.1
1789632

Escherichia coli

ldhA
NP_415898.1
16129341

Escherichia coli

ldh
YP_725182.1
113866693

Ralstonia eutropha

bdh
AAA58352.1
177198

Homo sapiens

adh
AAA23199.2
60592974

Clostridium

beijerinckii NRRL B593

adh
P14941.1
113443

Thermoanaerobacter

brockii HTD4

sadh
CAD36475
21615553

Rhodococcus ruber

adhA
AAC25556
3288810

Pyrococcus furiosus

BM92_14160
AHZ23715.1
631806019

Haloferax mediterranei

ATCC 33500

Step M, FIG. 11: 2,4-Pentadienoyl-CoA Hydrolase

CoA hydrolysis of 2,4-pentadienoyl CoA can be catalyzed by CoA hydrolases or thioesterases in the EC class 3.1.2. Several CoA hydrolases with broad substrate ranges are suitable enzymes for hydrolyzing these intermediates. For example, the enzyme encoded by acot12 from Rattus norvegicus brain (Robinson et al., Biochem. Biophys. Res. Commun. 71:959-965 (1976)) can react with butyryl-CoA, hexanoyl-CoA and malonyl-CoA. The human dicarboxylic acid thioesterase, encoded by acot8, exhibits activity on glutaryl-CoA, adipyl-CoA, suberyl-CoA, sebacyl-CoA, and dodecanedioyl-CoA (Westin et al., J. Biol. Chem. 280:38125-38132 (2005)). The closest E. coli homolog to this enzyme, tesB, can also hydrolyze a range of CoA thiolesters (Naggert et al., J Biol Chem 266:11044-11050 (1991)). A similar enzyme has also been characterized in the rat liver (Deana R., Biochem Int 26:767-773 (1992)). Additional enzymes with hydrolase activity in E. coli include ybgC, paaI, yciA, and ybdB (Kuznetsova, et al., FEMS Microbiol Rev, 2005, 29(2):263-279; Song et al., J Biol Chem, 2006, 281(16):11028-38). Though its sequence has not been reported, the enzyme from the mitochondrion of the pea leaf has a broad substrate specificity, with demonstrated activity on acetyl-CoA, propionyl-CoA, butyryl-CoA, palmitoyl-CoA, oleoyl-CoA, succinyl-CoA, and crotonyl-CoA (Zeiher et al., Plant. Physiol. 94:20-27 (1990)) The acetyl-CoA hydrolase, ACH1, from S. cerevisiae represents another candidate hydrolase (Buu et al., J. Biol. Chem. 278:17203-17209 (2003)).

GenBank

Gene name
Accession #
GI#
Organism

acot12
NP_570103.1
18543355

Rattus norvegicus

tesB
NP_414986
16128437

Escherichia coli

acot8
CAA15502
3191970

Homo sapiens

acot8
NP_570112
51036669

Rattus norvegicus

tesA
NP_415027
16128478

Escherichia coli

ybgC
NP_415264
16128711

Escherichia coli

paal
NP_415914
16129357

Escherichia coli

ybdB
NP_415129
16128580

Escherichia coli

ACH1
NP_009538
6319456

Saccharomyces cerevisiae

yciA
NP_415769.1
16129214

Escherichia coli

Yet another candidate hydrolase is the glutaconate CoA-transferase from Acidaminococcus fermentans. This enzyme was transformed by site-directed mutagenesis into an acyl-CoA hydrolase with activity on glutaryl-CoA, acetyl-CoA and 3-butenoyl-CoA (Mack et al., FEBS. Lett. 405:209-212 (1997)). This suggests that the enzymes encoding succinyl-CoA:3-ketoacid-CoA transferases and acetoacetyl-CoA:acetyl-CoA transferases may also serve as candidates for this reaction step but would require certain mutations to change their function.

GenBank

Gene name
Accession #
GI#
Organism

gctA
CAA57199
559392

Acidaminococcus fermentans

gctB
CAA57200
559393

Acidaminococcus fermentans

GenBank

Gene name
Accession #
GI#
Organism

hibch
Q5XIE6.2
146324906

Rattus norvegicus

hibch
Q6NVY1.2
146324905

Homo sapiens

hibch
P28817.2
2506374

Saccharomyces cerevisiae

BC_2292
AP09256
29895975

Bacillus cereus

Methylmalonyl-CoA is converted to methylmalonate by methylmalonyl-CoA hydrolase (EC 3.1.2.7). This enzyme, isolated from Rattus norvegicus liver, is also active on malonyl-CoA and propionyl-CoA as alternative substrates (Kovachy et al., J. Biol. Chem., 258: 11415-11421 (1983)).

Steps H, K and N, FIG. 11: 2-Oxopentenoate:Acetyl CoA Transferase, 2-Hydroxypentenoate:Acetyl-CoA CoA Transferase, 2,4-Pentadienoyl-CoA:Acetyl CoA CoA Transferase

Several transformations require a CoA transferase to activate carboxylic acids to their corresponding acyl-CoA derivatives. CoA transferase enzymes have been described in the open literature and represent suitable candidates for these steps. These are described below.

The gene products of cat1, cat2, and cat3 of Clostridium kluyveri have been shown to exhibit succinyl-CoA, 4-hydroxybutyryl-CoA, and butyryl-CoA transferase activity, respectively (Seedorf et al., Proc. Natl. Acad. Sci U.S.A 105:2128-2133 (2008); Sohling et al., J Bacteriol. 178:871-880 (1996)). Similar CoA transferase activities are also present in Trichomonas vaginalis, Trypanosoma brucei, Clostridium aminobutyricum and Porphyromonas gingivalis (Riviere et al., J. Biol. Chem. 279:45337-45346 (2004); van Grinsven et al., J. Biol. Chem. 283:1411-1418 (2008)).

A fatty acyl-CoA transferase that utilizes acetyl-CoA as the CoA donor is acetoacetyl-CoA transferase, encoded by the E. coli atoA (alpha subunit) and atoD (beta subunit) genes (Korolev et al., Acta Crystallogr. D. Biol. Crystallogr. 58:2116-2121 (2002); Vanderwinkel et al., 33:902-908 (1968)). This enzyme has a broad substrate range on substrates of chain length C3-C6 (Sramek et al., Arch Biochem Biophys 171:14-26 (1975)) and has been shown to transfer the CoA moiety to acetate from a variety of branched and linear 3-oxo and acyl-CoA substrates, including isobutyrate (Matthies et al., Appl Environ. Microbiol 58:1435-1439 (1992)), valerate (Vanderwinkel et al., Biochem. Biophys. Res. Commun. 33:902-908 (1968)) and butanoate (Vanderwinkel et al., Biochem. Biophys. Res. Commun. 33:902-908 (1968)). This enzyme is induced at the transcriptional level by acetoacetate, so modification of regulatory control may be necessary for engineering this enzyme into a pathway (Pauli et al., Eur. J Biochem. 29:553-562 (1972)). Similar enzymes exist in Corynebacterium glutamicum ATCC 13032 (Duncan et al., Appl Environ Microbiol, 68:5186-5190 (2002)), Clostridium acetobutylicum (Cary et al., Appl Environ Microbiol 56:1576-1583 (1990); Wiesenborn et al., Appl Environ Microbiol 55:323-329 (1989)), and Clostridium saccharoperbutylacetonicum (Kosaka et al., Biosci. Biotechnol Biochem. 71:58-68 (2007)).

Gene
GI #
Accession No.
Organism

atoA
2492994
P76459.1

Escherichia coli

atoD
2492990
P76458.1

Escherichia coli

actA
62391407
YP_226809.1

Corynebacterium glutamicum

cg0592
62389399
YP_224801.1

Corynebacterium glutamicum

ctfA
15004866
NP_149326.1

Clostridium acetobutylicum

ctfB
15004867
NP_149327.1

Clostridium acetobutylicum

ctfA
31075384
AAP42564.1

Clostridium

saccharoperbutylacetonicum

ctfB
31075385
AAP42565.1

Clostridium

saccharoperbutylacetonicum

Step L, FIG. 11: 2-hydroxypentenoyl-CoA Dehydratase

The dehydration of 2-hydroxypentenoyl-CoA can be catalyzed by a special class of oxygen-sensitive enzymes that dehydrate 2-hydroxyacyl-CoA derivatives by a radical-mechanism (Buckel and Golding, Annu. Rev. Microbiol. 60:27-49 (2006); Buckel et al., Curr. Opin. Chem. Biol. 8:462-467 (2004); Buckel et al., Biol. Chem. 386:951-959 (2005); Kim et al., FEBS J. 272:550-561 (2005); Kim et al., FEMS Microbiol. Rev. 28:455-468 (2004); Zhang et al., Microbiology 145 (Pt 9):2323-2334 (1999)). One example of such an enzyme is the lactyl-CoA dehydratase from Clostridium propionicum, which catalyzes the dehydration of lactoyl-CoA to form acryloyl-CoA (Kuchta and Abeles, J. Biol. Chem. 260:13181-13189 (1985); Hofmeister and Buckel, Eur. J. Biochem. 206:547-552 (1992)). An additional example is 2-hydroxyglutaryl-CoA dehydratase encoded by hgdABC from Acidaminococcus fermentans (Muëller and Buckel, Eur. J. Biochem. 230:698-704 (1995); Schweiger et al., Eur. J. Biochem. 169:441-448 (1987)). Purification of the dehydratase from A. fermentans yielded two components, A and D. Component A (HgdC) acts as an activator or initiator of dehydration. Component D is the actual dehydratase and is encoded by HgdAB. Variations of this enzyme have been found in Clostridum symbiosum and Fusobacterium nucleatum. Component A, the activator, from A. fermentans is active with the actual dehydratse (component D) from C. symbiosum and is reported to have a specific activity of 60 per second, as compared to 10 per second with the component D from A. fermentans. Yet another example is the 2-hydroxyisocaproyl-CoA dehydratase from Clostridium difficile catalyzed by hadBC and activated by hadI (Darley et al., FEBS J. 272:550-61 (2005)). The sequence of the complete C. propionicium lactoyl-CoA dehydratase is not yet listed in publicly available databases. However, the sequence of the beta-subunit corresponds to the GenBank accession number AJ276553 (Selmer et al, Eur J Biochem, 269:372-80 (2002)). The dehydratase from Clostridium sporogens that dehydrates phenyllactyl-CoA to cinnamoyl-CoA is also a potential candidate for this step. This enzyme is composed of three subunits, one of which is a CoA transferase. The first step comprises of a CoA transfer from cinnamoyl-CoA to phenyllactate leading to the formation of phenyllactyl-CoA and cinnamate. The product cinnamate is released. The dehydratase then converts phenyllactyl-CoA into cinnamoyl-CoA. FldA is the CoA transferase and FldBC are related to the alpha and beta subunits of the dehydratase, component D, from A. fermentans.

GenBank

Gene
Accession No.
GI No.
Organism

hgdA
P11569
296439332

Acidaminococcus fermentans

hgdB
P11570
296439333

Acidaminococcus fermentans

hgdC
P11568
2506909

Acidaminococcus fermentans

hgdA
AAD31676.1
4883832

Clostridum symbiosum

hgdB
AAD31677.1
4883833

Clostridum symbiosum

hgdC
AAD31675.1
4883831

Clostridum symbiosum

hgdA
EDK88042.1
148322792

Fusobacterium nucleatum

hgdB
EDK88043.1
148322793

Fusobacterium nucleatum

hgdC
EDK88041.1
148322791

Fusobacterium nucleatum

FldB
Q93AL9.1
75406928

Clostridium sporogens

FldC
Q93AL8.1
75406927

Clostridium sporogens

hadB
YP_001086863
126697966

Clostridium difficile

hadC
YP_001086864
126697967

Clostridium difficile

hadI
YP_001086862
126697965

Clostridium difficile

lcdB
AJ276553
7242547

Clostridium propionicum

Another dehydratase that can potentially conduct such a biotransformation is the enoyl-CoA hydratase (4.2.1.17) of Pseudomonas putida, encoded by ech that catalyzes the conversion of 3-hydroxybutyryl-CoA to crotonyl-CoA (Roberts et al., Arch. Microbiol 117:99-108 (1978)). This transformation is also catalyzed by the crt gene product of Clostridium acetobutylicum, the crt1 gene product of C. kluyveri, and other clostridial organisms Atsumi et al., Metab Eng 10:305-311 (2008); Boynton et al., J Bacteriol. 178:3015-3024 (1996); Hillmer et al., FEBS Lett. 21:351-354 (1972)). Additional enoyl-CoA hydratase candidates are phaA and phaB, of P. putida, and paaA and paaB from P. fluorescens (Olivera et al., Proc. Natl. Acad. Sci U.S.A 95:6419-6424 (1998)). The gene product of pimF in Rhodopseudomonas palustris is predicted to encode an enoyl-CoA hydratase that participates in pimeloyl-CoA degradation (Harrison et al., Microbiology 151:727-736 (2005)). Lastly, a number of Escherichia coli genes have been shown to demonstrate enoyl-CoA hydratase functionality including maoC (Park et al., J Bacteriol. 185:5391-5397 (2003)), paaF (Ismail et al., Eur. J Biochem. 270:3047-3054 (2003); Park et al., Appl. Biochem. Biotechnol 113-116:335-346 (2004); Park et al., Biotechnol Bioeng 86:681-686 (2004)) and paaG (Ismail et al., Eur. J Biochem. 270:3047-3054 (2003); Park and Lee, Appl. Biochem. Biotechnol 113-116:335-346 (2004); Park and Yup, Biotechnol Bioeng 86:681-686 (2004)).

GenBank

Gene
Accession No.
GI No.
Organism

ech
NP_745498.1
26990073

Pseudomonas putida

crt
NP_349318.1
15895969

Clostridium acetobutylicum

crt1
YP_001393856
153953091

Clostridium kluyveri

phaA
NP_745427.1
26990002

Pseudomonas putida KT2440

phaB
NP_745426.1
26990001

Pseudomonas putida KT2440

paaA
ABF82233.1
106636093

Pseudomonas fluorescens

paaB
ABF82234.1
106636094

Pseudomonas fluorescens

maoC
NP_4.15905.1
16129348

Escherichia coli

paaF
NP_415911.1
16129354

Escherichia coli

paaG
NP_415912.1
16129355

Escherichia coli

Alternatively, the E. coli gene products of fadA and fadB encode a multienzyme complex involved in fatty acid oxidation that exhibits enoyl-CoA hydratase activity (Yang et al., Biochemistry 30:6788-6795 (1991); Yang, J Bacteriol. 173:7405-7406 (1991); Nakahigashi et al., Nucleic Acids Res. 18:4937 (1990)). Knocking out a negative regulator encoded by fadR can be utilized to activate the fadB gene product (Sato et al., J Biosci. Bioeng 103:38-44 (2007)). The fadI and fadJ genes encode similar functions and are naturally expressed under anaerobic conditions (Campbell et al., Mol. Microbiol 47:793-805 (2003)).

Protein
GenBank ID
GI Number
Organism

fadA
YP_026272.1
49176430

Escherichia coli

fadB
NP_418288.1
16131692

Escherichia coli

fadI
NP_416844.1
16130275

Escherichia coli

fadJ
NP_416843.1
16130274

Escherichia coli

fadR
NP_415705.1
16129150

Escherichia coli

Throughout this application various publications have been referenced. The disclosures of these publications in their entireties, including GenBank and GI number publications, are hereby incorporated by reference in this application in order to more fully describe the state of the art to which this invention pertains. Although the invention has been described with reference to the examples provided above, it should be understood that various modifications can be made without departing from the spirit of the invention.

NON-NATURAL MICROBIAL ORGANISMS WITH IMPROVED ENERGETIC EFFICIENCY

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