An extended model, which relates the parameters of the conversion ratio of the substrate (c), the optical purity expressed as enantiormeric excess (ee), the enantiomeric ratio (E) and the equilibrium constant (K) in biochemical kinetic resolution of enantiomers, has been developed. The model predications have been verified experimentally via the enantioselective hydrolysis of ketoprofen methyl ester and the enantioselective esterification of ketoprofen in organic solvent. (c) 2006 Elsevier Ltd. All rights reserved.