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Assessing the stereoselectivity of carbonyl reductases toward the reduction of OPBE and docking analysis

The asymmetric reduction of prochiral carbonyl compounds by NAD(P)H‐dependent carbonyl reductases represents a powerful method for the production of optically active alcohols. The stereoselectivity of a series of carbonyl reductases were evaluated toward the reduction of ethyl 2‐oxo‐4‐phenylbutyrate (OPBE). A majority of reductases produced the ethyl (R)‐2‐hydroxy‐4‐phenylbutyrate ((R)‐HPBE) with low to excellent enantiomeric excess (e.e.), whereas about 30% reductases catalyzed OPBE to form (S)‐HPBE. Among them, the carbonyl reductase from Saccharomyces cerevisiae (SeCR) and short‐chain dehydrogenase from Gluconobacter oxydans (GoKR) exhibited 100% e.e., yielding the corresponding (R) and (S)‐HPBE, respectively. However, the SeCR showed relative higher activity (29.0 U/mg) and affinity (Km of 0.22 mM) than those of GoKR. Docking analysis found that the interaction of OPBE with enzyme‐NADPH complex determined the NADPH‐provided hydrogen transfer and the configuration of reductive product. These results indicated that the three‐dimensional (3D) structure of enzymes controlled the stereoselectivity of the reductive product based on the geometry of the substrate and cofactor.