Sequential kinetic resolution by two enantioselective enzymes

Enhancement of the enantioselectivity by simultaneous use of two enzymes in a sequential kinetic resolution process is presented. The model system consisted of carboxylesterase NP catalyzed hydrolysis of racemic methyl 2-chloropropionate, followed by dehalogenation of the enantiomerically enriched 2-chloropropionate by DL-dehalogenase into lactate. Optimal results are shown to be attained when the conversion rates of both faster reacting enantiomers are the same. An optimization parameter D for sequential resolutions is introduced. The kinetics of both reaction steps were investigated separately by progress curve analysis, and the enantioselectivity of the enzymes was determined. From a quantitative kinetic model we could formulate the sequential resolution, which yielded the predicted improvements of product enantiomeric excess.