Open AccessThe second nucleophile molecule binds to the acyl‐enzyme–nucleophile complex in α‐chymotrypsin catalysis
Author(s) -
GOLOLOBOV Mikhail Y.,
STEPANOV Valentin M.,
VOYUSHINA Tatjana L.,
ADLERCREUTZ Patrick
Publication year - 1993
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1993.tb18326.x
Subject(s) - nucleophile , chemistry , acylation , chymotrypsin , stereochemistry , acyl group , catalysis , enzyme , hydrolysis , medicinal chemistry , organic chemistry , group (periodic table) , trypsin
α‐Chymotrypsin‐catalyzed acyl tranfer was studied using three acyl‐group donors (Mal‐ l ‐Ala‐ l ‐Ala‐ l ‐PheOMe, Bz‐ l ‐TyrOEt and Ac‐ l ‐TrpOEt; Mal, maleyl; Bz, benzoyl; OMe, methyl ester; OEt, ethyl ester) and a series of amino‐acid amides. Most of the reactions studied can be described by the simplest kinetic model without the nucleophile binding to the acyl‐enzyme. The α‐chymotrypsin‐catalyzed transfer of the Mal‐ l ‐Ala‐ l ‐Ala‐ l ‐Phe group to the amides of L‐Phe and L‐Tyr showed a linear dependence of the partition constant, p , on the nucleophile concentration which can be interpreted by the hydrolysis of the acyl‐enzyme–nucleophile complex. The α‐chymotrypsin‐catalyzed transfer of the Bz‐ l ‐Tyr and Ac‐ l ‐Trp groups to several amino‐acid amides showed unusual behavior which can be interpreted by the kinetic model involving formation of a complex of the acyl‐enzyme with two nucleophile molecules. These observations can explain the conflicting conclusions concerning the kinetics of α‐chymotrypsin‐catalyzed acyl transfer evident in previous studies.