Stereoselective Oxidation of Aryl-Substituted Vicinal Diols into Chiral α-Hydroxy Aldehydes by Re-Engineered Propanediol Oxidoreductase

Abstract

α-Hydroxy aldehydes are chiral building blocks used in synthesis of natural products and synthetic drugs. One route to their production is by regioselective oxidation of vicinal diols and, in this work, we aimed to perform the oxidation of 3-phenyl-1,2-propanediol into the corresponding α-hydroxy aldehyde applying enzyme catalysis. Propanediol oxidoreductase from Escherichia coli efficiently catalyzes the stereoselective oxidation of S-1,2-propanediol into S-lactaldehyde. The enzyme, however, shows no detectable activity with aryl-substituted or other bulky alcohols. We conducted ISM-driven directed evolution on FucO and were able to isolate several mutants that were active with S-3-phenyl-1,2-propanediol. The most efficient variant displayed a kcat/KM of 40 s–1 M–1 and the most enantioselective variant an E-value (S/R) of 80. Furthermore, other isolated variants showed up to 4400-fold increased activity with another bulky substrate, phenylacetaldehyde. The results with engineered propanediol oxidoreducta...