ALKALINE PH DEPENDENCE OF δCHYMOTRYPSIN-CATALYZED HYDROLYSIS OF SPECIFIC SUBSTRATES*
Abstract
Km (app) and k cat for the δchymotrypsin-catalyzed hydrolysis of N-acetyl-L-tryptophan methyl ester and N-furylacryloyl-L-tryptophanamide were measured as a function of pH and ionic strength. The Km (app) values do not increase considerably above pH 9 for δ-chymotrypsin, as is the case with α-chymotrypsin. The observed kinetic difference between both enzymes at high pH suggests that the reversible inactivation of α-chymotrypsin at alkaline pH may involve the participation of tyrosine 146 or alanine 149 since both residues are present as chain termini in α-chymotrypsin but not in δ-chymotrypsin.
