Patent Grant
11034946
Fabry disease (MIM: 301500) is caused by a deficiency of the lysosomal enzyme alpha-galactosidase A (α-Gal A) that leads to early death due to occlusive disease of the heart, kidney, and brain. Clinical trials of enzyme replacement therapy for Fabry disease patients revealed only limited therapeutic efficacy and the enzyme does not pass the blood-brain barrier. There are significant side effects and many patients develop antibodies even in clinical trials that involve a single infusion of enzyme. It is recognized that there is a need for improved therapies for this disease. Clinical trials indicate that the immune response is correlated with the dose of enzyme administered. For example, therapeutic doses of 1.0 and 0.2 mg/kg body weight of alpha-galactosidase A result in 88% and 21% of patients with IgG response.
Hence there exists a long standing need to provide a treatment regimen that requires lower doses of enzyme, thereby providing for more effective therapeutic effects and less frequent infusions. In particular, there is a need to provide an enzyme therapeutic that allow for targeted delivery within the body and are sufficiently biologically active upon intracellular uptake.
In one embodiment, the present invention provides an engineered alpha-galactosidase A polypeptide comprising SEQ ID NO: 1 having at least one non-glycosylation mutation; and at least one glycosylation compensatory mutation.
In one embodiment, the engineered alpha-galactosidase A polypeptide disclosed herein includes at least one of the following mutations: V137P, G138P, N139Q, K140P, T141P, A190P, L191P, N192Q, R193P, T194P, K213P, N215Q, Y216P, and T217P.
In one embodiment, the engineered alpha-galactosidase A polypeptide disclosed herein includes at least one of the following mutations:Y134 R/K/E/D, V137 R/K/E/D, Y184 R/K/E/D, S188 R/K/E/D, S197 R/K/E/D, V199R/K/E/D, S201 R/K/E/D, C202 R/K/E/D, W204 R/K/E/D, P205 R/K/E/D, Y207 R/K/E/D, M208 R/K/E/D, W209 X/R/K/E/D, P210 R/K/E/D, F211X Q212 R/K/E/D, P214 R/K/E/D, and Y216 R/K/E/D,; wherein X is any amino acid except the native residue.
In one embodiment, the present invention provides a method of treating occlusive disease of the brain comprising administering to a patient in need thereof an effective amount of the engineered alpha-galactosidase A polypeptide disclosed herein.
In one embodiment, the present invention provides a method of treating Fabry disease comprising administering to a patient in need thereof an effective amount of the engineered alpha-galactosidase A polypeptide disclosed herein.
The patent or patent application contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the U.S. Patent and Trademark Office upon request and payment of the necessary fee.
The present disclosure provides non-glycosylated derivatives of alpha-galactosidase A or glycosylation independent alpha-galactosidase A. The non-glycosylated derivatives of alpha-galactosidase A or glycosylation independent alpha-galactosidase A disclosed herein includes an engineered alpha-galactosidase A polypeptide having at least one non-glycosylation mutation; and at least one glycosylation compensatory mutation.
There are four potential glycosylation sites, Asn139, Asn192 and Asn215, (Asn408 is not glycosylated) for human α-Gal A (
A non-glycosylation mutation is any mutation that causes loss of glycosylation at a natively glycosylated amino acid residue or site. The mutation may be a substitution mutation or deletion. A non-glycosylation mutation includes one or more mutations.
In one embodiment, substitution of the asparagine at N139, N192, or N215 with any amino acid other than asparagine will result in loss of glycosylation at positions 139, 192, or 215. Likewise, deletion of N139, N192, or N215 will result in loss of glycosylation. Furthermore, a substitution or deletion mutation that disrupts the N-glycosylation consensus sequence will result in loss of glycosylation. The N-glycosylation consensus being AsnXxxSer/Thr/Cys, where Xxx can be any amino acid except proline.
In one embodiment, one or more of the following mutations result in loss of glycosylation at N139: V137P, G138P, N139Q, K140P, and T141P.
In one embodiment, one or more of the following mutations result in loss of glycosylation at N192: A190P, L191P, N192Q, R193P, and T194P.
In one embodiment, one or more of the following mutations result in loss of glycosylation at N215: K213P, N215Q, Y216P, and T217P.
In one embodiment, the non-glycosylation mutation includes deletion of at least one of N139, N192, and N215.
The present disclosure provides compensatory mutations that restore functionality of the non-glycosylated alpha-galactosidase A enzyme described above. As used herein, a mutation that improves alpha-galactosidase A enzyme (having a non-glycosylation mutation) function is a glycosylation compensatory mutation.
It has been discovered that one or more mutations of amino acid residues at or near the normally glycosylated locations (N139, N192, and N215) to a polar or charged amino acid will restore functionality lost by non-glycosylation at one or more of N139, N192, and N215. Without wishing to be bound by theory, it is believed that glycosylation at positions N139, N192, and N215 interact with neighboring hydrophobic side chains, and loss of glycosylation results in protein misfolding, and solubility and aggregation issues. Hydrophobic amino acid residues are known in the art, and include Ala (A), Val (V), Ile (I), Leu (L), Met (M), Phe (F), Tyr (Y), and Trp (W). Therefore, substitution of neighboring hydrophobic residues with polar or uncharged amino acid residues will compensate for the loss of glycosylation.
The glycosylation compensatory mutation may be within 5, within 10, or within 20 amino acids from the normally glycosylated location, which is nonglycosylated.
Polar or charged amino acid residues are known in the art. Polar or charged amino acid residues include Ser (S), Thr (T), Cys (C), Tyr (Y), Gln (Q), Asp (D), Glu (E), Lys (K), Arg (R), and His (H).
In one embodiment, the present disclosure provides an engineered alpha-galactosidase A polypeptide having a non-glycosylation mutation at one or more of positions N139, N192 and N215; and compensatory mutation at one or more of positions: Y134, V137, Y184, S188, S197, V199, S201, C202, W204, P205, Y207, M208, W209, P210, F211, Q212, P214, Y216, and T217.
In another embodiment, the compensatory mutation includes substitution of the WT amino acid residue at Y134, V137, F145, Y184, S188, S197, V199, S201, C202, W204, P205, Y207, M208, W209, P210, F211, Q212, P214, Y216, T217 and Y222, with a polar or charged amino acid residue.
In another embodiment, the compensatory mutation is selected from the group consisting of: Y134R/K/E/D, V137R/K/E/D, Y184 R/K/E/D, S188 R/K/E/D, S197 R/K/E/D, V199R/K/E/D, S201R/K/E/D, C202R/K/E/D, W204R/K/E/D, P205R/K/E/D, Y207R/K/E/D, M208R/K/E/D, W209X/R/K/E/D, P210R/K/E/D, F211X Q212R/K/E/D, P214R/K/E/D, and Y216R/K/E/D,; wherein X is any amino acid except the native residue.
In one embodiment, the engineered alpha-galactosidase A polypeptide includes a non-glycosylation mutation selected from the group consisting of V137P, G138P, N139Q, K140P, and T141P. In this embodiment, the glycosylation compensatory mutation is selected from the group consisting of Y134 R/K/E/D, V137 R/K/E/D, and F145 R/K/E/D. Alternatively, in this embodiment, the glycosylation compensatory mutation is a deletion of one or more of Y134 and V137.
In one embodiment, the engineered alpha-galactosidase A polypeptide includes a non-glycosylation mutation is selected from the group consisting of A190P, L191P, N192Q, R193P, and T194P. In this embodiment, the glycosylation compensatory mutation is selected from the group consisting of Y184 R/K/E/D, S188 R/K/E/D, S197 R/K/E/D, and V199 R/K/E/D. Alternatively, in this embodiment, the compensatory mutation is a deletion selected from the group consisting of Y184, S188, S197, and V199.
In one embodiment, the engineered alpha-galactosidase A polypeptide includes a non-glycosylation mutation selected from the group consisting of K213P, N215Q, Y216P, and T217P. In this embodiment, the glycosylation compensatory mutation may be at least one of S197 R/K/E/D, V199 R/K/E/D, S201 R/K/E/D, C202 R/K/E/D, W204 R/K/E/D, P205 R/K/E/D, Y207 R/K/E/D, M208 R/K/E/D, W209 X/R/K/E/D, P210 R/K/E/D, F211X, Q212 R/K/E/D, P214 R/K/E/D, Y216 R/K/E/D, and Y222 R/K/E/D. Alternatively, in this embodiment, the compensatory mutation may be at least one deletion selected from the group consisting of S197, V199, S201, C202, W204, P205, Y207, M208, W209, P210, F211 Q212, P214, and Y216.
In one embodiment, the non glycosylation mutation is selected from the group consisting of K213P, N215Q, Y216P, and T217P; and the glycosylation compensatory mutation is a deletion or substitution of least one of M208, W209, P210 and F211.
In one embodiment, the non-glycosylation mutation is N215Q and the glycosylation compensatory mutation is at least one of M208E and F211X. In one embodiment, F211X is selected from the group consisting of F211H, F211R, F211K, F211E, and F211D.
Functional variants of the engineered polypeptides disclosed herein have been contemplated. As used herein, a functional variant includes a polypeptide having at least 99%, at least 95%, at least 90%, or at least 80% identity to SEQ ID NO: 1; wherein SEQ ID NO: 1 includes at least one non-glycosylation mutant, and at least one glycosylation compensatory mutation. Functional variants may be derived from non-human sources.
Functional fragments of the engineered polypeptides disclosed herein have been contemplated. As used herein, a functional fragment includes a polypeptide having between 400-428, 400-420, or 375-400 consecutive amino acids of SEQ ID NO: 1, wherein SEQ ID NO: 1 includes at least one non-glycosylation mutant and at least one glycosylation compensatory mutation.
In one embodiment, the present disclosure provides a polynucleotide that encodes for the engineered polypeptide disclosed herein. In one embodiment, the polynucleotide is in a vector.
Other mutations that aid in dimer stability increased catalysis have been contemplated. Such mutations are described in U.S. Provisional Application Nos. 62/207,856 and 62/207,849; and U.S. patent application Ser. No. 15/243,637, all of which are incorporated by reference in their entirety.
The present disclosure provides methods of treating Fabry disease by administering the engineered polypeptides disclosed herein to a patent in need thereof.
The engineered alpha-galactosidase polypeptide provides improved expression. The disclosed polypeptide may be expressed in systems without the need of glycosylation. Therefore, the polypeptides disclosed herein may be expressed in prokaryotes. In one embodiment, the present disclosure provides for expression of the engineered alpha-galactosidase polypeptide in e. coli.
The engineered alpha-galactosidase polypeptide disclosed herein provides improved ability to cross the blood brain barrier. In one embodiment, the engineered alpha-galactosidase polypeptide disclosed herein may be used to treat occlusive disease of the brain.
The engineered alpha-galactosidase polypeptide disclosed herein provides increased resistance to protease and therefore provides increased half-life in the patient to which it is administered.
The protein or polypeptide of the invention can be produced by conventional chemical methods, such as solid phase synthesis (using e.g. FMOC and BOC techniques), and solution phase synthesis. These proteins or polypeptides may also be produced in bacterial or insect cells or other eukaryotic transcriptional in vivo system, as detailed in the below-noted Current Protocols in Molecular Biology, Chapter 16. Following production, the protein or polypeptide are purified from the cells in which they have been produced. Polypeptide purification and isolation methods are known to the person of skill in the art and are detailed e.g., in Ausubel et al. (eds.) Current Protocols in Molecular Biology, Chapter 16, John Wiley and Sons, 2006 and in Coligan et al. (eds.). Current Protocols in Protein Science, Chapters 5 and 6, John Wiley and Sons, 2006. Advantageously, the protein or polypeptide may be produced as a fusion with a second protein, such as Glutathione-S-transferase (GST) or the like, or a sequence tag, such as the Histidine tag (His-tag) sequence. The use of fusion or tagged proteins simplifies the purification procedure, as detailed in the above-noted Current Protocols in Molecular Biology, Chapter 16, and in the instructions for His-tag protein expression and purification kits [available, e.g. from Qiagen GmbH, Germany].
As used herein, the term “purified” refers to a compound (e.g., alpha galctosidase A and derivatives disclosed herein) having been separated from a component of the composition in which it was originally present. The term purified can sometimes be used interchangeably with the term “isolated”. Thus, for example, “purified or isolated quercetin” has been purified to a level not found in nature. A “substantially pure” compound or molecule is a compound or molecule that is lacking in most other components (e.g., 30, 40, 50, 60, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, 100% free of contaminants). By opposition, the term “crude” means compounds or molecules that have not been separated from the components of the original composition in which it was present. Therefore, the terms “separating”, “purifying” or “isolating” refers to methods by which one or more components of the biological sample are removed from one or more other components of the sample. A separating or purifying step preferably removes at least about 70% (e.g., 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, 100%), more preferably at least about 90% (e.g., 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%) and, even more preferably, at least about 95% (e.g., 95, 96, 97, 98, 99, 100%) of the other components present in the sample from the desired component. For the sake of brevity, the units (e.g., 66, 67 . . . 81, 82, . . . 91, 92% . . . ) have not systematically been recited but are considered, nevertheless, within the scope of the present invention.
In accordance with one embodiment, the delivery system and/or delivery vehicle can be provided in conjunction with a local drug delivery apparatus. A local drug delivery apparatus can be a medical device for implantation into a treatment site of a living organism and can include at least one delivery vehicle and/or a therapeutic agent in a therapeutic dosage releasably affixed to the medical device. A local delivery apparatus can include a material for preventing the delivery vehicle and/or the therapeutic agent from separating from the medical device prior to implantation of the medical device at the treatment site, the material being affixed to the medical device or a component of the delivery system.
A delivery vehicle and/or a therapeutic agent may be affixed to any number of medical devices. For example, the delivery vehicles and systems can be associated with or fixed with pumps, catheters, or implants. A delivery system may be affixed to minimize or substantially eliminate the biological organism's reaction to the introduction of the medical device utilized to treat a separate condition. For example, stents, catheters, implants, balloons, self-expandable or nor, degradable or not, can be utilized in conjunction with the delivery system.
The components of the delivery system can be administered in vivo by use of a pharmaceutically acceptable carrier in the form of a composition. By “pharmaceutically acceptable” is meant a material that is not biologically or otherwise undesirable, i.e., the material may be administered to a subject, along with the components of the delivery system, without causing any undesirable biological effects or interacting in a deleterious manner with any of the other components of the pharmaceutical composition in which it is contained. The carrier would naturally be selected to minimize any degradation of the active ingredient and to minimize any adverse side effects in the subject, as would be well known to one of skill in the art.
Suitable carriers and their formulations are described in Remington: The Science and Practice of Pharmacy (19th ed.) ed. A. R. Gennaro, Mack Publishing Company, Easton, Pa. 1995. Typically, an appropriate amount of a pharmaceutically-acceptable salt is used in the formulation to render the formulation isotonic. Examples of pharmaceutically-acceptable carriers include, but are not limited to, saline, Ringer's solution and dextrose solution. The pH of the solution is preferably from about 5 to about 8, and more preferably from about 7 to about 7.5. Further carriers include sustained release preparations such as semipermeable matrices of solid hydrophobic polymers containing the delivery system, which matrices are in the form of shaped articles, e.g., films. It will be apparent to those persons skilled in the art that certain carriers may be more preferable depending upon, for instance, the route of administration and concentration of composition being administered.
Pharmaceutical compositions for use in conjunction with the delivery system may include carriers, thickeners, diluents, buffers, preservatives, surface active agents and the like in addition to the delivery vehicle and/or the therapeutic agent. Pharmaceutical compositions may also include one or more active ingredients such as antimicrobial agents, anti-inflammatory agents, anesthetics, and the like.
A pharmaceutical composition may be administered in a number of ways depending on whether local or systemic treatment is desired, and on the area to be treated. Administration may be topically (including ophthalmically, vaginally, rectally, intranasally), orally, by inhalation, or parenterally, for example by intravenous drip, subcutaneous, intraperitoneal or intramuscular injection. The delivery system can be administered intravenously, intraperitoneally, intramuscularly, subcutaneously, intracavity, or transdermally.
Parenteral administration, if used, is generally characterized by injection. Injectables can be prepared in conventional forms, either as liquid solutions or suspensions, solid forms suitable for solution of suspension in liquid prior to injection, or as emulsions. A more recently revised approach for parenteral administration involves use of a slow release or sustained release system such that a constant dosage is maintained.
Preparations for parenteral administration can include sterile aqueous or non-aqueous solutions, suspensions, and emulsions. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils such as olive oil, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, alcoholic/aqueous solutions, emulsions or suspensions, including saline and buffered media. Parenteral carriers include sodium chloride solution, Ringer's dextrose, dextrose and sodium chloride, lactated Ringer's, or fixed oils. Intravenous vehicles include fluid and nutrient replenishers, electrolyte replenishers (such as those based on Ringer's dextrose), and the like.
Preservatives and other additives may also be present such as, for example, antimicrobials, anti-oxidants, chelating agents, and inert gases and the like.
Formulations for topical administration may include ointments, lotions, creams, gels, drops, suppositories, sprays, liquids and powders. Conventional pharmaceutical carriers, aqueous, powder or oily bases, thickeners and the like may be necessary or desirable.
Further, unless expressly stated to the contrary, “or” refers to an inclusive “or” and not to an exclusive “or”. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
In this specification, groups of various parameters containing multiple members are described. Within a group of parameters, each member may be combined with any one or more of the other members to make additional sub-groups. For example, if the members of a group are a, b, c, d, and e, additional sub-groups specifically contemplated include any one, two, three, or four of the members, e.g., a and c; a, d, and e; b, c, d, and e; etc.
The present invention is illustrated in further details by the following non-limiting examples.
In Situ Enzyme Assay for Colonies of P. pastoris Using the Artificial Substrate X-a-Gal.
In situ enzyme assays used nitrocellulose membranes (No. 21850, 0.45-mm pore size, VWR, Plainfield, N.J.) placed on YPDS petri plates with zeocin (100 mg/ml). Colonies that grew on selective media after electroporation were patched onto the membranes using sterile wooden toothpicks (Diamond Brands, Inc., Minneapolis, Minn.). The colonies were grown directly on the membrane overnight at 30° C. and then transferred to the surface of an MM plate for the enzyme induction by methanol. After incubation at 30° C. overnight, the membranes with colonies growing on top of them were placed on Whatman No. 4 filters (No. 1001 125, Whatman, Inc., Clifton, N.J.) saturated with the chromogenic substrate X-a-gal (No. 917591, Boehringer Mannheim, Indianapolis, Ind.) solution (1 mg/ml) in 40 mM sodium acetate, pH 4.5, and incubated at 37° C. Those colonies positive for a-galactosidase A activity were visualized by a change in color from light yellow to blue 1 to 3 h after exposure to the substrate. This assay was adapted from Zhu, A., Monahan, C., Zhang, Z., Hurst, R., Leng, L., and Goldstein, J. (1995) High-level expression and purification of coffee bean a-galactosidase produced in the yeast Pichia pastoris. Arch. Biochem. Biophys. 324, 65-70.
A colorimetric patch test is used to test the ability of compensatory mutations to rescue non-glycosylation alpha-galactosidase A mutants.
Compensatory mutations were introduced (e.g., M208E) that stabilize the enzyme activity of a glycosylation negative (site 3) α-Gal A N215Q mutant (
The glycosylation independent derivatives of the human α-Gal A disclosed herein are used for in vitro mutagenesis and directed evolution experiments in Escherichia coli and Pichia pastoris to further optimize enzyme activity and function.
GREEN - potential compensatory mutation sites for N139Q and N192Q: Y134, and
Cell Strains and Plasmids.
The P. pastoris host strain X-33 (No. K1740-01), E. coli strains TOP10 (No. C4040-50) and TOP10F′ (No. C665-11), plasmid pPICZαA (No. K1740-01), and TOPO® XL PCR cloning kit (No. K4700-10) were purchased from Invitrogen.
Bioreactor Expression of Recombinant αGal in P. pastoris.
High-cell-density fermentation was carried out as previously described (Chen 2000) with a modified growth medium utilizing non-precipitating sodium hexametaphosphate as a phosphate source (Zhang 2000) and modified for a 7 L Applikon bioreactor. Fermentation medium of 3.5 L (0.93 g/l CaSO4, 18.2 g/l K2SO4, 14.9 g/l MgSO4.7 H2O, 9 g/l (NH4)2SO4, 40.0 g/l glycerol) was autoclaved at 121° C. for 20 min in the vessel. After cooling to room temperature, filter sterilized sodium hexametaphosphate (25 g/l of fermentation basal salt medium dissolved in 500 ml of deionized water) and 0.435% PTM1 trace elements (CuSO4.5 H2O 6.0 g, NaI 0.08 g, MgSO4.H2O 3.0 g, Na2MoO4.2 H2O 0.2 g, H3BO3 0.02 g, CoCl2 0.5 g, ZnCl2 20.0 g, FeSO4.7 H2O 65.0 g, biotin 0.2 g, 5.0 ml H2SO4 per liter) were added to complete the fermentation medium. The pH was adjusted to 6.0 using ammonium hydroxide (28%).
Four frozen MGY cultures of 4 ml each were used to inoculate four 100 ml MGY cultures in 1-liter baffled flasks and grown at 250 rpm and 30° C. until the OD600 reached 2 to 6. The cultivation was divided into three phases, the glycerol batch, glycerol-fed batch, and methanol-fed batch. The glycerol batch phase was initiated with 400 ml of inoculum shake-flask culture added to 4 L of the fermentation medium containing 4% glycerol and an initial value of 100% dissolved oxygen until a spike was observed indicating complete consumption of glycerol. Next, the glycerol-fed batch phase was initiated and a 50% w/v glycerol feed rate of 18.15 ml/h/liter initial fermentation volume and maintained until a cell yield of 180 to 220 g/liter wet cells was achieved. At this point the glycerol feed was terminated manually and a methanol-fed batch phase was initiated by starting a 100% methanol feed containing 12 ml PTM1 trace salts per liter. Methanol was initially fed at 3.6 ml/h/liter of initial fermentation volume, then increased to 7.3 ml/h/liter and finally increased to 10.9 ml/h/liter of initial fermentation volume for the remainder of the fermentation. Dissolved oxygen spikes were used during the glycerol-fed batch phase and methanol-fed batch phase and to monitor substrate levels. A dissolved oxygen level of 40%, pH of 6, and temperature of 25° C. were maintained by an ADI 1030 regulator. Sampling was performed at the end of each phase and at lease twice daily and analyzed for cell wet weight and increased αGal activity over time. Cultivation was terminated once a plateau in αGal activity was observed.
Purification of αGal Using Double Affinity Chromatography.
Purification was as described (Chen 2000, Yasuda 2004) with minor modifications (below). Bioreactor supernatant was passed through a 0.2 μm hollow fiber filter (Spectrum Labs, No. M22M-300-01N) and subjected to diafiltration using a 50 kDa pore size hollow fiber filter (Spectrum Labs, No. M25S-300-01N) against wash buffer (0.1 M sodium acetate buffer, pH 6.0, 0.1 M NaCl, 1 mM MgCl2, 1 mM CaCl2, 1 mM MnCl2). The resulting supernatant was applied to a Con A Sepharose 4B (GE Healthcare No. 17-0440-01) column, pre-equilibrated with wash buffer, and washed with 5 column volumes of wash buffer. It was observed that near-saturating sugar eluent concentrations do not improve glycoprotein recovery as compared to lower concentrations and that elution phase pauses improve recovery. In accordance with these findings, elution of αGal was carried out using modified elution buffer I (0.5 M methyl-α-d-mannopyranoside, 0.25 M methyl-α-d-glucopyranoside in wash buffer) over 1.5 column volume blocks separated by 12-hour interval soaks. Elution was discontinued when the absorbance at 280 nm and enzyme assays showed negligible presence of protein and αGal activity. No substantial difference in recovered enzyme was observed between purifications carried out with modified elution buffer I versus sugar saturated elution buffer I (data not shown). The Con A pool was subjected to diafiltration using a 50 kDa pore size hollow fiber filter (Spectrum Labs, No. M25S-300-01N) against binding buffer (25 mM citrate-phosphate buffer, pH 4.8 containing 0.1 M NaCl).
The Con A pool was applied to an immobilized-d-galactose gel column (Thio-Gal, Pierce No. 20372) pre-equilibrated with binding buffer. The column was washed with 5 column volumes of binding buffer and αGal was eluted with elution buffer II (25 mM citrate-phosphate buffer, pH 5.5, 0.1 M NaCl, 0.1 M d-galactose) over 1.5 column volume blocks separated by 12 hour soaks. Fractions were assayed for enzyme activity and protein concentration and a peak tube with high specific activity was chosen as the sample to be used in a substrate saturation curve.
The purification protocol is modified for the purification of the Y207W mutant of alpha-galactosidase A. For this mutant, DEAE (Diethylaminoethyl) and SP (sulphopropyl, strong cation exchange) affinity media are used for purification. See
Electrophoresis Analysis
Samples (8 μg) were mixed with an equal volume of reducing sample buffer (Bio-Rad Laemmli sample buffer with 5% β-mercaptoethanol) and heated for 5 minutes at 95° C. before loading on a Mini-Protean TGX Precast Gel 4-20% (w/v) (Bio-Rad No. 456-1094). Bands were visualized by Coomassie blue staining via the modified Fairbanks protocol.
Western Blot Analysis
Western blot analysis was performed using an anti-αGal polyclonal antibody produced in chicken (Pierce/ThermoSci #PA1-9528) and horseradish peroxidase-conjugated anti-Chicken IgY antibody (Sigma #A9046). After SDS-PAGE (2 μg of samples loaded), the gel was incubated with a nitrocellulose membrane (Whatman, No. 10402594) for 15 minutes at room temperature in Transfer Buffer (48 mM Tris, 39 mM glycine, 20% MeOH, pH 9.2) and the proteins were then transferred to the nitrocellulose membrane using a Bio-Rad Trans Blot SD Semi-Dry Transfer Cell. The membrane was blocked with 8% (w/v) non-fat dried milk in PBST [10 mM Na2HPO4, 1.8 mM KH2PO4, 137 mM NaCl, 2.7 mM KCl and 0.2% Tween 20 (pH 7.4)] at room temperature for 20 minutes. The membrane was then treated with primary antibody diluted in a milk/blot solution [1% (w/v) non-fat dried PBST] for 2 h at room temperature with mild shaking. After rinsing with PBST solution, the membrane was treated for 1 h at room temperature with secondary antibody diluted in the milk/blot solution. Protein bands were visualized on Kodak BioMax XAR film (VWR #1B1651454) with a Konica SRX-101A processor.
Enzyme and Protein Assays
Activity of αGal was assayed using the synthetic substrate, 4-methylumbelliferyl-α-d-galactopyranoside (MUG) as described (Chen 2000) with modifications to a microtiter plate format (below). Enzyme activity is measured in units/ml where one unit is defined as the amount of enzyme required to convert 1 nmole of MUG to 4-methylumbelliferone in one hour at 37° C. An aliquot of 3 μl was added to 27 μl of enzyme assay buffer (5 mM MUG in 40 mM sodium acetate buffer, pH 4.5). This mixture was incubated at 37° C. and 10 μl aliquots were taken at two time points and added to 290 μl of 0.1 M diethylamine in a microtiter plate to stop the reaction. Typically time points were chosen as 1-4 minutes and values that were proportional to time were considered valid. The fluorescence of each sample was measured at an excitation wavelength of 365 nm and an emission wavelength of 450 nm using a Tecan Infinite F200 microtiter plate reader. A standard curve of 10 μl of 0-0.5 nmol 4-methylumbelliferone dissolved in MeOH in 290 μl of 0.1 M diethylamine was used to quantitate MUG cleavage at specific time intervals. Analysis of the effects of MeOH indicated no effect on the 4-methylumbelliferone standard curve.
For samples containing higher protein concentrations, the BioRad DC Protein Assay (No. 500-0116) with a standard curve of (0.2-1.5) mg/ml was used according to the manufacturer's specifications. For dilute samples of purified αGal, a more sensitive fluorescence-based fluorescamine assay with a standard curve containing lower protein concentrations of (4.0-160) μg/ml was used. Briefly, 150 μl of 0.05 M sodium phosphate buffer and 50 μl of 1.08 mM fluorescamine dissolved in acetone were added to an aliquot of 50 μl of the sample and standards, mixed and incubated for 12 minutes. The fluorescence of each sample was measured at an excitation wavelength of 400 nm and an emission wavelength of 460 nm. Bovine serum albumin (Bio-Rad No. 500-0112) was used as the standard in both assays. Absorbance and fluorescence measurements were conducted on a Tecan Infinite F200 microplate reader using 96-well plates.
Mass Spectrometry of a Purified Mutant Enzyme
Mass spectrometry is used to analyze the mutant enzyme. SDS-PAGE gel slices are washed, de-stained, reduced using 10 mM dithiothreitol, alkylated using 100 mM iodoacetamide, and digested using trypsin. Peptides are then extracted from the gel two times, dried, and re-suspended in a 5% acetonitrile and 2% formic acid mixture. One third of each sample is loaded onto a C18 PepMap1000 micro-precolumn (300 μm I.D., 5 mm length, 5 μm beads, Thermo Scientific) at a flow-rate of 5 μl/min, and subsequently onto an analytical C18 column (75 μm I.D., 3 μm beads, Nikkyo Technos Co.) at a flow rate of 300 nl/min. The gradient was 40 min long in the range 5 to 45% B (buffer A was 0.1% formic acid in water, and buffer B was 0.1% formic acid in acetonitrile). Eluted peptides are applied by electrospray directly into the LTQ-Orbitrap XL mass spectrometer from Thermo Scientific, operating in a 300 to 1800 m/z mass range. Tandem mass spectrometry was performed by collision induced dissociation using nitrogen as a collision gas. The resulting spectra were analyzed using Mascot and Proteome Discoverer 1.3 (Thermo Scientific) to identify the peptides in the sample.
Thermostability and pH Optimum of WT and Mutant αGal
Purified enzyme samples are diluted in 25 mM citrate-phosphate buffer, pH 5.5, 0.1 M NaCl, 0.01 M D-galactose. Samples of 50 μl were incubated in triplicate at 50° C., 30° C., and 40° C. Aliquots of 3 μl are removed for enzyme assays every 15 minutes for two hours. Samples are assayed in 0.02 M citrate buffer, pH 3.0-pH 6.5, containing 2 mM MUG.
Characterization of Kinetic Properties
Substrate saturation curves for αGal have been reported using MUG at concentrations up to 2 mM, 5 mM, and 10 mM (in the presence of 0.1% BSA and 0.67% EtOH). We noted that under our experimental conditions MUG is fully soluble at 2 mM, partially soluble at 5 mM, and chemically oversaturated at higher concentrations. Other investigators reported the use of sonication or detergent treatment to increase the solubility of MUG, but we avoided this approach in order to avoid potential artifacts due to the use of these techniques. Substrate saturation curves using 2 mM and 5 mM MUG as the highest concentrations were carried out and the kinetic parameters for αGal were calculated separately obtaining similar values. The values reported here were obtained using a substrate saturation curve of 0.3 to 2 mM MUG since this is the highest concentration that is fully soluble under our experimental conditions. The Km and Vmax values were calculated using Lineweaver-Burk and non-linear regression through the program Sigma-Plot (Systat Software, San Jose, Calif.).
Kinetic parameters were also determined using the colorimetric substrate, para-nitrophenyl-α-d-galactopyranoside (PNPaGal) [70]. Purified enzymes were diluted to approximately 20,000 units/mL as determined by fluorescent MUG assay. These diluted samples were then added at a proportion of 1:9 citrate-phosphate buffer (0.1 M) containing 7-50 mM PNPαGal. Aliquots of 20 μl of the enzymatic reaction were removed at 15 minute intervals to terminate the reaction over the course of an hour and added to 320 μl of borate buffer (pH 9.8) in a microplate [71]. Product formation was monitored by absorbance at 400 nm. Linear reaction velocities were observed for all measurements. A standard curve of 0-150 μM p-nitrophenylate in borate buffer (pH 9.8) [71] was used to quantitate product formation. Km and Vmax parameters were determined through non-linear regression using Sigma-Plot (Systat Software, San Jose, Calif.).
Protein Structure Analysis
The crystal structure of αGal (PDB 1R47) was viewed and analyzed in PyMOL (Delano Scientific). The MSLDKLL and QMSLKDLL peptides corresponding to the last 7 or 8 C-terminal amino acids of αGal were built in PyRosetta [72] and visualized in PyMOL [73]. Interatomic distances were measured using the PyMOL wizard distance command.
A homology model of the coffee bean α-galactosidase was generated on the Phyre2 server. The primary sequence of coffee bean α-galactosidase (GenBank No. AAA33022.1) was set as the query. The crystal structure of rice α-galactosidase (73% sequence identity to coffee α-galactosidase, PDB#1UAS) was set as the template. Superposition of the coffee homolog and human crystal structure of αGal (PDB#1R47) was conducted in PyMOL. Primary sequence alignments were carried out in ClustalOmega (EMBL-EBI).
In Situ Enzyme Assay.
In situ enzyme assay for colonies of P. pastoris using the artificial substrate X-a-Gal. In situ enzyme assays (12) used nitrocellulose membranes (No. 21850, 0.45-mm pore size, VWR, Plainfield, N.J.) placed on YPDS petri plates with zeocin (100 mg/ml). Colonies that grew on selective media after electroporation were patched onto the membranes using sterile wooden toothpicks (Diamond Brands, Inc., Minneapolis, Minn.). The colonies were grown directly on the membrane overnight at 30° C. and then transferred to the surface of an MM plate for the enzyme induction by methanol. After incubation at 30° C. overnight, the membranes with colonies growing on top of them were placed on Whatman No. 4 filters (No. 1001 125, Whatman, Inc., Clifton, N.J.) saturated with the chromogenic substrate X-a-gal (No. 917591, Boehringer Mannheim, Indianapolis, Ind.) solution (1 mg/ml) in 40 mM sodium acetate, pH 4.5, and incubated at 37° C. Those colonies positive for a-galactosidase A activity were visualized by a change in color from light yellow to blue 1 to 3 h after exposure to the substrate. This assay was adapted from Zhu, A., Monahan, C., Zhang, Z., Hurst, R., Leng, L., and Goldstein, J. (1995) High-level expression and purification of coffee bean a-galactosidase produced in the yeast Pichia pastoris. Arch. Biochem. Biophys. 324, 65-70.
A polypeptide having different combinations of E203C, Y207W, E203N, M208E, W209X, F211X, F211H, and N215Q mutations.
The in situ enzyme assay described above was used to test the following engineered alpha-galactosidase A polypeptides: WT; and combinations of E203C, Y207W, E203N, M208E, W209X, F211X, F211H, and N215Q. See
WT alpha-galactosidase A polypeptide was expressed and purified by the methods described above.
Characterization of kinetic properties where determined as described above. Table 1 provides the various kinetic parameters. See below for the 0Lineweaver-Burke plot showing the same.
Alpha-galactosidase A polypeptides having the Y207W mutation and W277C mutation are expressed and purified by methods described above.
See
Engineered alpha-galactosidase A polypeptide having the M208E/N215Q mutation was expressed and purified by the methods described above.
Characterization of kinetic properties where determined as described above. Table 2 provides the various kinetic parameters. See below for the Lineweaver-Burke plot showing the same.
See
While there have been described what are presently believed to be the preferred embodiments of the present invention, those skilled in the art will realize that other and further changes and modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such modifications and changes as come within the true scope of the invention.
Incorporated herein by reference in its entirety is the Sequence Listing for the above-identified Application. The Sequence Listing is disclosed on a computer-readable ASCII text file titled “Sequence_Listing_1038-158.txt”, created on Oct. 5, 2018. The sequence.txt file is 7.5 KB in size.
The present application claims the benefit of U.S. Provisional Application Ser. No. 62/568,534 filed on Oct. 5, 2017, which is hereby incorporated by reference in its entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5179023 | Calhoun | Jan 1993 | A |
| Entry |
|---|
| Stokes. Sep. 2017. Mutagenesis of human alpha-galactosidase A for the treatment of Fabry Disease. On the World Wide Web at: academicworks.cuny.edu/gc_etds/2338/. |
| Number | Date | Country | |
|---|---|---|---|
| 20190106691 A1 | Apr 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62568534 | Oct 2017 | US |
