alpha-Chymotrypsin deacylation: temperature dependence of hydrolysis and transesterification reactions.

The hydrolysis and transesterification reactions of furoyl-chymotrypsins display nonlinear Arrhenius plots with no apparent discontinuities. Of a number of models considered, the best explanation assumes a temperature-dependent rapid equilibrium between two forms of acyl-enzyme with differing reactivities. Rate constants for the transesterification of alpha-chymotrypsinyl 2-(5-n-propyl)furoate, after normalization for this equilibrium, display a linear free energy correlation with the Taft polarity constants sigma* and volumes of the attacking alcohols.