Open AccessCharacterization of the S′‐subsite specificity of bovine pancreatic α‐chymotrypsin via acyl transfer to added nucleophiles
Author(s) -
SCHELLENBERGER Volker,
SCHELLENBERGER Ute,
MITIN Yuri V.,
JAKUBKE HansDieter
Publication year - 1990
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1990.tb15290.x
Subject(s) - nucleophile , chemistry , residue (chemistry) , stereochemistry , chymotrypsin , acyl group , carboxylate , peptide , enzyme , acylation , nucleophilic acyl substitution , organic chemistry , catalysis , biochemistry , trypsin , group (periodic table)
The S′‐subsite specificity of bovine pancreatic α‐chymotrypsin was investigated by acyl transfer reactions using a series of amino‐acid‐ and peptide‐derived nucleophiles. The nucleophilic efficiency covers a range of more than three orders of magnitude, reflecting the specificity of the acyl transfer process. Positively charged H‐Arg‐NH 2 was the most efficient nucleophile of the series while peptides with free carboxyl groups show poor nucleophilic behaviour. This is explained by electrostatic interactions with the residues Asp35 and Asp64 of the enzyme. These negatively charged groups, which are localized near the appropriate S′ binding sites, repel carboxylate groups of the nucleophiles. There is a good correlation between the nucleophile efficiencies found for different acyl enzymes. An investigation of a series of 14 water‐soluble acyl donor esters, differing both in the P 1 residue and in the number of amino acids, revealed that the nature of the acyl group affected the acyl‐enzyme partitioning between water and added nucleophile in the range of one order of magnitude.