Intrinsic effects of solvent polarity on enzymic activation energies.

The effect of organic solvents on subtilisin Carlsberg catalysis has been investigated with the aid of a thermodynamic analysis. Saturation solubility experiments were performed to provide a quantitative measure of substrate desolvation from the reaction medium. This enabled calculation of the intrinsic enzymic activation energy and resulted in a linear free energy relationship with respect to solvent polarity. The results indicate that the intrinsic activation energy of subtilisin catalysis is lowest in polar organic solvents, which may be due to transition state stabilization of the enzyme's polar transition state for transesterification. Copyright 2000 John Wiley & Sons, Inc.