Action of Pepsin on Synthetic Substrates

II. Diglycyl-L-phenylalanyl-L-phenylalanyl (and L-tyrosyl)-glycines: Sensitive Synthetic Substrates for Pepsin

Abstract

A study was carried out to find a sensitive synthetic substrate for pepsin [EC3. 4. 4. 1] which is soluble in acidic buffer and shows no transpeptidation reaction. Several oligopeptides, Gly_m-Tyr₂-Gly_n (m=1, 2, 3, and 4; n=1, 2, and 3) and Gly₂-X-Y-Gly (X and Y, Tyr or Phe), soluble in acidic buffer, were synthesized and subjected to the action of pepsin. Analyses of an incubation mixture by paper chromatography and by an amino acid analyzer proved that the substrates are hydrolyzed at the peptide bond linking the two aromatic amino acid residues with no indication of any transpeptidation reaction. Among the series of the substrates, Gly₂-Phe-Phe-(and Tyr)-Gly were most susceptible to hydrolysis, and are recommended as convenient synthetic substrates for pepsin.