Kinetic study on conformational effect in hydrolysis of p-nitroanilides catalyzed by α-chymotrypsin

Abstract

Effects of medium viscosity on kinetics for the hydrolysis of p-nitroanilides of certain amino acid derivatives catalyzed by α-chymotrypsin have been investigated. Observed data indicate that the overall rate constant, k_cat, is hardly affected by the medium viscosity in all the substrates employed and equals the rate constant at the acylation step, k₂, in the measured range of viscosity. By comparison with the data on p-nitrophenyl ester substrates reported previously, it is concluded that the formation of the tetrahedral intermediate in the course of the acylation of the enzyme is influenced by conformational change of the enzyme, whereas the breakdown of the intermediate is almost free from conformational effects.