A disulfide-bridged peptide drug development candidate contained two oligopeptide chains with 11 and 12 natural amino acids joined by a disulfide bond at the N-terminal end. An efficient biotechnology based process for the production of the disulfide-bridged peptide was developed. Initially, the two individual oligopeptide chains were prepared separately by designing different fusion proteins and expressing them in recombinant E. coli. Enzymatic or chemical cleavage of the two fusion proteins provided the two individual oligopeptide chains which could be conjugated via disulfide bond by conventional chemical reaction to the disulfide-bridged peptide. A novel heterodimeric system to bring the two oligopeptide chains closer and induce disulfide bond formation was designed by taking advantage of the self-assembly of a leucine zipper system. The heterodimeric approach involved designing fusion proteins with the acidic and basic components of the leucine zipper, additional amino acids to optimize interaction between the individual chains, specific cleavage sites, specific tag to ensure separation, and two individual oligopeptide chains. Computer modeling was used to identify the nature and number of amino acid residue to be inserted between the leucine zipper and oligopeptides for optimum interaction. Cloning and expression in rec E. coli, fermentation, followed by cell disruption resulted in the formation of heterodimeric protein with the interchain disulfide bond. Separation of the desired heterodimeric protein, followed by specific cleavage at methionine by cyanogen bromide provided the disulfide bridged peptide.

(R)-5,5,5-Trifluoronorvaline, an intermediate for a gamma-secretase inhibitor (BMS-708163) under development, was initially prepared from the corresponding keto acid using a commercially available D-amino acid dehydrogenase for reductive amination and glucose dehydrogenase for cofactor recycling. This amino acid could also be prepared using a D-amino acid transaminase with alanine as the amino donor, but the transamination also requires lactate dehydrogenase, NAD, formate, and formate dehydrogenase to remove pyruvate in order to bring the reaction to completion. An effective proprietary D-amino acid dehydrogenase was constructed by modification of the D-diaminopimelic acid dehydrogenase gene from Bacillus sphaericus, and a glucose dehydrogenase gene was cloned from Gluconobacter oxidans. Both genes were expressed in the same strain of Escherichia coli, and the glutamate dehydrogenase gene was inactivated in the expression strain to eliminate background production of the S-amino acid and improve the ee of the product to 100%. The amino acid could be isolated or converted without isolation to a p-chlorophenylsulfonamide carboxamide intermediate needed for the synthetic route to the gamma-secretase inhibitor development candidate.

N-Cbz-4,5-dehydro-l-prolineamide or N-Boc-4,5-dehydro-l-prolineamide are alternative key intermediates for the synthesis of saxagliptin, a dipeptidyl peptidase IV (DPP4) inhibitor recently approved for treatment of type 2 diabetes mellitus. An efficient biocatalytic method was developed for conversion of l-ornithine, N-α-benzyloxycarbonyl (Cbz)-l-ornthine, and N-α-tert-butoxycarbonyl (Boc)-l-ornithine to 5-hydroxy-l-proline, N-Cbz-5-hydroxy-l-proline, and N-Boc-5-hydroxy-l-proline, respectively. Rec. Escherichia coli expressing lysine-ɛ-aminotransferase and rec Pichia pastoris expressing l-ornithine oxidase were used for these conversions. N-Cbz-5-hydroxy-l-proline, and N-Boc-5-hydroxy-l-proline were chemically converted to key intermediates N-Cbz-4,5-dehydro-l-prolineamide and N-Boc-4,5-dehydro-l-prolineamide, respectively.

A synthetic gene encoding a Streptomyces l-proline-3-hydroxylase was constructed and used to produce the hydroxylase protein in recombinant Escherichia coli. A fermentation process for growth of this recombinant E. coli for enzyme production was scaled-up to 250L. A biotransformation process was developed using cell suspensions of the recombinant E. coli and subsequently scaled-up to 10L for conversion of l-proline to cis-3-hydroxy-l-proline. A reaction yield of 85 M% and d.e. of 99.9% was obtained for cis-3-hydroxy-l-proline.

The enantioselective microbial reduction of 6-oxo-8-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butyl]-8-azaspiro[4.5]decane-7,9-dione (1) to either of the corresponding (S)- and (R)-6-hydroxy-8-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butyl]-8-azaspiro[4.5]decane-7,9-diones (2 and 3, respectively) is described. The NADP+-dependent (R)-reductase (RHBR) which catalyzes the reduction of 6-ketobuspirone (1) to (R)-6-hydroxybuspirone (3) was purified to homogeneity from cell extracts of Hansenula polymorpha SC 13845. The subunit molecular weight of the enzyme is 35,000kDa based on sodium dodecyl sulfate gel electrophoresis and the molecular weight of the enzyme is 37,000kDa as estimated by gel filtration chromatography. (R)-reductase from H. polymorpha was cloned and expressed in Escherichia coli. To regenerate the cofactor NADPH required for reduction we have cloned and expressed the glucose-6-phosphate dehydrogenase gene from Saccharomyces cerevisiae in E. coli. The NAD+-dependent (S)-reductase (SHBR) which catalyzes the reduction of 6-ketobuspirone (1) to (S)-6-hydroxybuspirone (2) was purified to homogeneity from cell extracts of Pseudomonas putida SC 16269. The subunit molecular weight of the enzyme is 25,000kDa based on sodium dodecyl sulfate gel electrophoresis. The (S)-reductase from P. putida was cloned and expressed in E. coli. To regenerate the cofactor NADH required for reduction we have cloned and expressed the formate dehydrogenase gene from Pichia pastoris in E. coli. Recombinant E. coli expressing (S)-reductase and (R)-reductase catalyzed the reduction of 1 to (S)-6-hyroxybuspirone (2) and (R)-6-hyroxybuspirone (3), respectively, in >98% yield and >99.9% e.e.

A novel enantioselective N-carbobenzyloxy (Cbz)-cleaving enzyme was purified to homogeneity from Sphingomonas paucimobilis SC 16113. The gene encoding the protein has been identified and its complete DNA sequence was determined. The Cbz-cleaving enzyme was expressed in Escherichia coli.

The chiral intermediate (S)-1-(2'-bromo-4'-fluoro phenyl)ethanol 2 was prepared by the enantioselective microbial reduction of 2-bromo-4-fluoro acetophenone 1. Organisms from genus Candida, Hansenula, Pichia, Rhodotorula, Saccharomyces, Sphingomonas and Baker's yeast reduced 1 to 2 in >90% yield and 99% enantiomeric excess (ee). In an alternative approach, the enantioselective microbial reductions of methyl, ethyl, and tert-butyl 4-(2'-acetyl-5'-fluorophenyl) butanoates 3, 5, and 7, respectively, were demonstrated using strains of Candida and Pichia. Reaction yields of 40-53% and ee's of 90-99% were obtained for the corresponding (S)-hydroxy esters 4, 6, and 8. The reductase, which catalyzed the enantioselective reduction of ketoesters was purified to homogeneity from cell extracts of Pichia methanolica SC 13825. It was cloned and expressed in Escherichia coli with recombinant cultures used for the enantioselective reduction of keto methyl ester 3 to the corresponding (S)-hydroxy methyl ester 4. On a preparative scale, a reaction yield of 98% and an ee of 99% was obtained. (C) 2004 Elsevier Ltd. All rights reserved.

[4S-(4I.7I,10aJ)]1-Octahydro-5-oxo-4-[phenylmethoxy)carbonyl]amino]-7H-pyrido-[2,1-b] [1,3]thiazepine-7-carboxylic acid methyl ester (BMS-199541-01) is a key chiral intermediate for the synthesis of Omapatrilat (BMS-186716), a new vasopeptidease inhibitor under development. By using a selective enrichment culture technique we have isolated a strain of Sphingomonas paucimobilis SC 16113, which contains a novel L-lysine epsilon-aminotransferase. This enzyme catalyzed the oxidation of the epsilon-amino group of lysine in the dipeptide dimer N-2-[N[phenyl-methoxy)-carbonyl] L-homocysteinyl] L-lysine)1,1-disulphide (BMS-201391-01) to produce BMS-199541-01. The aminotransferase reaction required alpha-ketoglutarate as the amino acceptor. Glutamate formed during this reaction was recycled back to alpha-ketoglutarate by glutamate oxidase from Streptomyces noursei SC 6007. Fermentation processes were developed for growth of S. paucimobilis SC 16113 and S. noursei SC 6007 for the production of L-lysine epsilon-amino transferase and glutamate oxidase, respectively. L-lysine epsilon-aminotransferase was purified to homogeneity and N-terminal and internal peptides sequences of the purified protein were determined. The mot wt of L-lysine epsilon-aminotransferase is 81 000 Da and subunit size is 40 000 Da. L-lysine epsilon-aminotransferase gene (lat gene) from S. paucimobilis SC 16113 was cloned and overexpressed in Escherichia coli. Glutamate oxidase was purified to homogeneity from S. noursei SC 6003. The mol wt of glutamate oxidase is 125 000 Da and subunit size is 60 000 Da. The glutamate oxiadase gene from S. noursei SC 6003 was cloned and expressed in Streptomyces lividans. The biotransformation process was developed for the conversion of BMS-201391-01 to BMS-199541-01 by using L-lysine epsilon-aminotransferase expressed in E. coli. In the biotransformation process, for conversion of BMS-201391-01 (CBZ protecting group) to BMS-199541-01, a reaction yield of 65-70 65-70 M% was obtained depending upon reaction conditions used in the process. Phenylacetyl or phenoxyacetyl protected analogues of BMS-201391-01 also served as substrates for L-lysine epsilon-aminotransferase giving reaction yields of 70 M% for the corresponding BMS-199541-01 analogs. Two other dipeptides N-[N[(phenylmethoxy)carbonyl]-L-methionyl]-L-lysine (BMS-203528) and N,2-[S-acetyl-N-[(phenylmethoxy)carbonyl]-L-homocysteinyl]-L-lysine (BMS-204556) were also substrates for L-lysine epsilon-aminotransferase. N-alpha-protected (CBZ or BOC)-L-lysine were also oxidized by L-lysine E-aminotransferase. (C) 2000 Elsevier Science Inc. All rights reserved.