Cloning, expression, and characterization of an anti-Prelog stereospecific carbonyl reductase from Gluconobacter oxydans DSM2343

A new anti-Prelog stereospecific carbonyl reductase (GoKR) from Gluconobacter oxydans DSM2343 was cloned and identified in Escherichia coli. This GoKR formed a homo-tetramer with a subunit size of approximately 27.0 kDa. GoKR exhibited full activity with NADPH but not with NADH as a cofactor. The optimal pH and temperature were 9.0 and 30 degrees C, respectively. GoKR reduced various ketones, including aliphatic and aromatic ketones, alpha- and beta-keto esters. Aromatic ketones were reduced to (R)-enantiomers, whereas keto esters were reduced to (S)-hydroxy esters with different enantioselectivities. The data indicate that GoKR does not obey Prelog's rule and exhibits anti-Prelog enantiopreference. Enzyme-substrate-cofactor docking analysis showed that hydride transfer occurred at the si faces of carbonyl group for ethyl 4-chloro-3-oxobutanoate (COBE), which was then selectively reduced to the chiral (S)-alcohol. Excellent enantioselectivities were obtained for reducing CUBE and ethyl 2-oxo-4-phenylbutyrate into the corresponding (S)-type products. These products are important for synthesizing HMG-CoA reductase (statins) and angiotensin-converting enzyme inhibitors, respectively. (C) 2014 Elsevier Inc. All rights reserved.