I. Structural analogs of typical substrates of alpha-chymotrypsin. II. 1-acetyl-2-[L-tyrosyl] hydrazine : an inhibitor of alpha-chymotrypsin. III. Binuclear aromatics as inhibitors of alpha-chymotrypsin-catalyzed hydrolyses. IV. Applicability of the pH-stat to alpha-chymotrypsin-catalyzed hydrolyses that produce a buffer

Abstract

Substitution of a nitrogen atom in place of the C-H group that occurs at the asymmetric center of typical substrates of alpha-chymotrypsin results in the complete loss of the ability of the enzyme to catalyze the hydrolysis of the carboethoxy or carboxamido group. However, the nitrogen-substituted analogs, which otherwise possess all of the remaining significant structural entities of typical substrates, function as inhibitors of alpha-chymotrypsin catalyzed hydrolyses but in general show less affinity for the enzyme than do the analogous C-H containing substrates. It has been found that l-acetyl-2-[L-tyrosyl] hydrazine is a reversible inhibitor of alpha-chymotrypsin catalyzed hydrolyses with unusual affinity for the enzyme. At pH 7.9 the enzyme inhibitor constant was found to have a value of KI = 0.074 x 10(-3)M, which shows that this substance associates reversibly with alpha-chymotrypsin at the active site to a greater extent than any other known substrate or reversible inhibitor. Preliminary results, based upon inhibition studies, indicate that alpha-chymotrypsin possesses a greater affinity for the naphthalene function than for the indole function. A study of the applicability of the pH-stat to alpha-chymotrypsin catalyzed hydrolyses that produce a buffer showed that the reliability was a function of the buffer capacity. Amides gave poor results; hydrazides gave good or fair results, one of which contradicted a literature value, and a hydroxamide gave excellent results.