Application of directed evolution in the development of enantioselective enzymes*

A novel approach to developing enantioselective enzymes for use in organic chemistry has been devised which is independent of structural or mechanistic aspects. The underlying idea is to combine appropriate methods of random mutagenesis, gene expression, and high-throughput screening for enantioselectivity. If these actions are performed in repetitive cycles, an evolutionary pressure is created that leads to sequential improvements of the enantioselectivity of a given enzyme-catalyzed reaction. The concept is illustrated by an example involving the lipase-catalyzed hydrolytic kinetic resolution of an α-chiral ester, the enantioselectivity increasing from ee = 2% (E = 1.1) for a wild-type enzyme to ee = 90–93% (E = 25) for the best mutants.