Action of Pepsin on Synthetic Substrates

I. Hydrolysis and Transpeptidation of Peptides Ranging from Glycyl-L-tyrosyl-L-tyrosine to Triglycyl-L-tyrosyl-L-tyrosine

Abstract

A series of Gly_n-Tyr-Tyr (n=1, 2 and 3) were synthesized, and the mode of action of pepsin [EC 3.4.4.1] on these substrates was studied. Analyses of products were made by applying a new assay method using an amino acid analyzer and by means of paper chromatography. The analyses of incubation mixture of Gly_n-Tyr-Tyr (n=1-3) proved that in addition to the hydrolysis at a peptide bond of Tyr-Tyr sequence the substrates are subjected to a transpeptidation reaction. However, Gly-Tyr₂ was remarkably less susceptible than Gly₂- and Gly₃-Tyr₂. The mode of action of pepsin on known substrates, acetyl-Tyr-Tyr and benzyloxycarbonyl-Glu-Tyr. was also studied by the use of an amino acid analyzer.