Highly Enantioselective Reduction of Carbonyl Compounds Using a Reductase Purified from Bakers' Yeast

An NADPH-dependent reductase that shows reducing activity for 1-chloro-2-hexanone has been purified from bakers' yeast. SDS-PAGE and gel filtration suggested that the purified reductase is a monomeric enzyme with a molecular weight of ca. 37 kDa. Asymmetric reduction of several carbonyl compounds using the purified reductase has been carried out. 1-Chloro-2-hexanone, 1-acetoxy-2-heptanone, methyl acetoacetate, ethyl pyruvate, 1-chloro-2,4-pentanedione, and 2,4-hexanedione were reduced to the corresponding alcohols with high enantiomeric purities (>98% ee). The reductase showed high specificity constants (k_cat/K_m = 10³-10⁵ s^-1 M^-1) and relatively low Michaelis constants (K_m = 10^-4-10^-3 M) for all the substrates examined.