Directed evolution of selective enzymes and hybrid catalysts

The methods of directed evolution, developed in the 1990s, can be applied successfully to the creation of enantioselective enzymes for use in synthetic organic chemistry. The combination of appropriate molecular biological methods for random mutagenesis and expression coupled with high-throughput screening systems for the determination of ee-values forms the basis of this novel approach to asymmetric catalysis. The principle is illustrated by the dramatic enhancement of enantioselectivity of a lipase as the catalyst in the hydrolytic kinetic resolution of a chiral ester, the selectivity factor improving from E=1.1 to E=51. Reversal of enantioselectivity is also possible. Finally, the concept of directed evolution of selective hybrid catalysts has been delineated.