title: Effects of pH on carboxypeptidase-Y-catalyzed hydrolysis and aminolysis reactions.
abstract: The pH dependencies of serine carboxypeptidase-Y-catalysed hydrolysis and aminolysis reactions using L-amino acids and L-amino acid amides as nucleophiles, have been studied and analyzed. The results reveal two catalytically important ionizing groups of the enzyme with rather similar pK values (5-6), the active site His397 and a possibly Glu residue, which is not only important in interactions with carboxylic groups of substrates and nucleophiles [Liao, D.-I., Breddam, K., Sweet, R. M., Bullock, T. & Remmington, S. J. (1992) Biochemistry 31, 9796-9812], but also indirectly play a role in catalysis. This explains the pH behaviour of hydrolysis of both peptide and ester substrates and further, that L-amino acid amides are better nucleophiles in aminolysis reactions than L-amino acids.
authors.affiliation: University of Copenhagen, Department of Chemistry, Denmark.
authors.forename: U
authors.initials: U
authors.lastname: Christensen
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D001665:Binding Sites; D002268:Carboxypeptidases / Q000737:chemistry / Q000378:metabolism*; D043402:Cathepsin A; D004151:Dipeptides; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D004151:Dipeptides; D029701:Saccharomyces cerevisiae Proteins; D002268:Carboxypeptidases; D043402:Cathepsin A; C499283:PRC1 protein, S cerevisiae; C022633:serine carboxypeptidase