Chiral Recognition Of Alcohol Enantiomers In Acyl Transfer Reactions Catalysed ByCandida AntarcticaLipase B

A description of the substrate-enzyme interactions involved in the discrimination of see-alcohol enantiomers in acyl transfer reactions catalysed by the highly enantioselective Candida antarctica lipase B is presented. 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 stereoselective substrate-enzyme interactions. Matching experimental and calculated results allowed conclusions regarding the orientation of the tetra-hedral intermediates in the active site. The finding, valid for substrates of a specific activity above 1 mol min-1 mg-1 protein, describes the origin of enantioselectivity as a combination of a binding site of limited size, the ”stereospecificity pocket“, and principally different productive orientations of the two enantiomers.