Asymmetric Reduction of 1-Acetoxy-2-alkanones with Bakers’ Yeast: Purification and Characterization of α-Acetoxy Ketone Reductase

An α-acetoxy ketone reducing enzyme has been purified and characterized from the cell-free extract of bakers’ yeast (Saccharomyces cerevisiae). Only one NADPH-dependent dehydrogenase that catalyzed the reduction of α-acetoxy ketone was found in bakers’ yeast. The molecular weight of the enzyme was estimated to be 36 kDa by SDS-polyacrylamide gel electrophoresis. The enzyme was composed of a single polypeptide chain. The enzyme had reducing activity for both aliphatic and aromatic α-acetoxy ketones, although no reducing activity toward α-chloro ketones and α-hydroxy ketones was found. The enzyme catalyzed the reduction of not only α-acetoxy ketones, but also β-keto esters. Studies on the chromatographic behavior and stereospecificity indicated that the enzyme was identical with one of the β-keto ester reductases purified from bakers’ yeast.