title: The inhibition of pepsin-catalysed reactions by products and product analogues. Kinetic evidence for ordered release of products.
abstract: 1. The inhibition of pepsin-catalysed hydrolysis of N-acetyl-l-phenylalanyl-l-phenylalanylglycine by products and product analogues was studied. 2. The non-competitive nature of the inhibition by the product N-acetyl-l-phenylalanine confirms an ordered release of products, and points to a common mechanism (involving an amino-enzyme) for pepsin-catalysed transpeptidation and hydrolysis reactions. 3. N-Acetyl-l-phenylalanine ethyl ester is also a non-competitive inhibitor, but here the inhibition is of the ;dead-end' type. No ethanol is detectable in reaction mixtures, indicating that this ester cannot act as an amino group acceptor in a transpeptidation process. 4. The same is true for N-methanesulphonyl-l-phenylalanine methyl and methyl thiol esters. No methanethiol is liberated when the methyl thiol ester is present as an inhibitor of the hydrolytic reaction, and the hope that such a thiol ester would effectively trap the amino-enzyme was not fulfilled.
mesh_terms: D000596:Amino Acids; D004952:Esters; D005998:Glycine; D007700:Kinetics; D010434:Pepsin A / Q000037:antagonists & inhibitors*; D010455:Peptides; D010649:Phenylalanine
chemical_list: D000596:Amino Acids; D004952:Esters; D010455:Peptides; D010649:Phenylalanine; D010434:Pepsin A; D005998:Glycine