title: Enantioselective reduction of carbonyl compounds by whole-cell biotransformation, combining a formate dehydrogenase and a (R)-specific alcohol dehydrogenase.
abstract: A whole-cell biotransformation system for the reduction of prochiral carbonyl compounds, such as methyl acetoacetate, to chiral hydroxy acid derivatives [methyl (R)-3-hydroxy butanoate] was developed in Escherichia coli by construction of a recombinant oxidation/reduction cycle. Alcohol dehydrogenase from Lactobacillus brevis catalyzes a highly regioselective and enantioselective reduction of several ketones or keto acid derivatives to chiral alcohols or hydroxy acid esters. The adh gene encoding for the alcohol dehydrogenase of L. brevis was expressed in E. coli. As expected, whole cells of the recombinant strain produced only low quantities of methyl (R)-3-hydroxy butanoate from the substrate methyl acetoacetate. Therefore, the fdh gene from Mycobacterium vaccae N10, encoding NAD+-dependent formate dehydrogenase, was functionally coexpressed. The resulting two-fold recombinant strain exhibited an in vitro catalytic alcohol dehydrogenase activity of 6.5 units mg-1 protein in reducing methyl acetoacetate to methyl (R)-3-hydroxy butanoate with NADPH as the cofactor and 0.7 units mg-1 protein with NADH. The in vitro formate dehydrogenase activity was 1.3 units mg-1 protein. Whole resting cells of this strain catalyzed the formation of 40 mM methyl (R)-3-hydroxy butanoate from methyl acetoacetate. The product yield was 100 mol% at a productivity of 200 micromol g-1 (cell dry weight) min-1. In the presence of formate, the intracellular [NADH]/[NAD+] ratio of the cells increased seven-fold. Thus, the functional overexpression of alcohol dehydrogenase in the presence of formate dehydrogenase was sufficient to enable and sustain the desired reduction reaction via the relatively low specific activity of alcohol dehydrogenase with NADH, instead of NADPH, as a cofactor.
authors.affiliation: Institut für Biotechnologie 1, Forschungszentrum Jülich GmbH, 52425, Julich, Germany.
authors.forename: Marianne
authors.initials: M
authors.lastname: Ernst
authors.forename: Björn
authors.initials: B
authors.lastname: Kaup
authors.forename: Michael
authors.initials: M
authors.lastname: Müller
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bringer-Meyer
authors.forename: Hermann
authors.initials: H
authors.lastname: Sahm
mesh_terms: D000090:Acetoacetates / Q000378:metabolism*; D000426:Alcohol Dehydrogenase / Q000235:genetics* / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000378:metabolism; D001711:Biotransformation; D003067:Coenzymes / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005560:Formate Dehydrogenases / Q000235:genetics* / Q000378:metabolism*; D007778:Lactobacillus / Q000201:enzymology / Q000235:genetics; D009161:Mycobacterium / Q000201:enzymology / Q000235:genetics; D009930:Organic Chemicals / Q000378:metabolism; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000090:Acetoacetates; D003067:Coenzymes; D009930:Organic Chemicals; D011994:Recombinant Proteins; C005217:methyl acetoacetate; D000429:Alcohol Oxidoreductases; D000426:Alcohol Dehydrogenase; C037212:formate dehydrogenase (NADP+); D005560:Formate Dehydrogenases