CHIRAL RECOGNITION OF ALCOHOL ENANTIOMERS IN ACYL TRANSFER-REACTIONS CATALYZED BY CANDIDA-ANTARCTICA LIPASE-B

A description of the substrate-enzyme interactions involved in the dis crimination of sec-alcohol enantiomers in acyl transfer reactions cata lysed by the highly enantioselective Candida antarctica lipase B is pr esented. Experimentally found activities and enantioselectivities from kinetic resolutions of a series of secondary alcohol substrates were used together with molecular modelling for the elucidation of the ster eoselective substrate-enzyme interactions. Matching experimental and c alculated results allowed conclusions regarding the orientation of the tetrahedral intermediates in the active site. The finding, valid for substrates of a specific activity above 1 mu mol min(-1) mg(-1) protei n, describes the origin of enantioselectivity as a combination of a bi nding site of limited size, the ''stereospecificity pocket'', and prin cipally different productive orientations of the two enantiomers.