The enantioselectivity of haloalkane dehalogenases

Two haloalkane dehalogenases were tested for their ability to perform kinetic resolutions of a series of racemic substrates and to convert meso substrates enantioselectively. For the kinetic resolutions E-values of up to 9 were measured and, in the conversions of the meso substrates, products were obtained with an enantiomeric excess of up to 47%. A kinetic analysis revealed that despite modest overall chiral recognition (expressed as E-values), there are large differences between the Km values (>100 fold) of two enantiomeric substrates but that these differences are compensated by correspondingly large differences in kcat.