Bbtechnol. Reg. 1994, 10, 403-409
409
Modification of the Enzyme Enantioselectivity by Product Inhibition J. L. L. Rakels,' P. Caillat, A. J. J. Straathof, and J. J. Heijnen Department of Biochemical Engineering, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
A kinetic explanation of solvent effects on the enantioselective hydrolysis of racemic methyl and ethyl 2-chloropropionate by carboxylesterase NP has been studied. After a general ping-pong model for the kinetic resolution of chiral esters was defined, the progress curves of the reactions were analyzed, and a simplified uni-uni four-parameter model was selected. First-order rate constants and alcohol inhibition constants were determined for both enantiomers. Enantiomeric excess values were correctly predicted from the model. According to the kinetic description, the enantioselectivity could be enhanced or decreased by adding the product alcohol as a cosolvent. It appeared that these changes could be predicted quantitatively by enantioselective product inhibition for alcohol concentrations
