Carbonyl reductase SCRII from Candida parapsilosis catalyzes anti-Prelog reaction to (S)-1-phenyl-1,2-ethanediol with absolute stereochemical selectivity

An (S)-specific carbonyl reductase (SCRII) was purified to homogeneity from Candida parapsilosis by following an anti-Prelog reducing activity of 2-hydroxyacetophenone. Peptide mass fingerprinting analysis shows SCRII belongs to short-chain dehydrogenase/reductase family. Its coding gene was cloned and overexpressed in Escherichia coli. The recombinant SCRII displays the similar enzymatic characterization and catalytic properties to SCR. It catalyzes the enantioselective reduction of 2-hydroxyacetophenone to (S)-1-phenyl-1,2-ethanediol with excellent optical purity of 100% in higher yield than SCR. Based on the sequence-structure alignment, several single-point mutations inside or adjacent to the substrate-binding loop or active site were designed. With respect to recombinant native SCRII, the A220 and E228 mutations almost lost enantioselectivity towards 2-hydroxyacetophenone reduction. The catalytic efficiencies (k_cat/. K_m) for the A220 or E228 variants are <7% that of the unmutated enzyme. This work provides an excellent catalyst for enantiopure alcohol preparation and the lethal mutations of A220 and E228 suggest their importance in substrate-binding and/or catalysis.