Thermodynamic analysis of solvent effect on substrate specificity of lyophilized enzymes suspended in organic media.

A simple methodology has been successfully employed to explain the solvent dependence of the substrate specificity of enzymes in organic media. This methodology, which does not require the knowledge of the enzyme structure and is thus applicable to lyophilized and other noncrystalline enzyme preparations, predicts that the k(cat)/K(M) ratio for two substrates should be proportional to their Raoult's law activity coefficients. This approach has been validated for two enzymes, subtilisin Carlsberg and alpha-chymotrypsin, catalyzing the propanolysis of unnatural (in addition to natural) ester substrates in a variety of anhydrous solvents.