Enzymatic hydrolysis of analogous saturated and unsaturated peptides.

Two types of peptidases are present in tissues, one of which catalyzes the hydrolysis of the saturated, RCHCONHCHR’COOH,l the other that of the unsaturated, RCHCONHC(=CHR’)COOH~RCHCON=C(CH~R’)COOH, peptide bonds (cf. (1)). These are designated, respectively, peptidases and dehydropeptidases. We have reported the rates of hydrolysis of variously constituted dehydropeptides in extracts of rat tissues (24). The present study consist’s in a comparison of such rates with those of analogous saturated peptides under nearly identical experimental conditions. Comparison has been made between glycyl-on-alanine and glycyldehydroalanine, glycyl-nn-phenylalanine and glycyldehydrophenylalanine, and chloroacetyl-nn-alanine and chloroacetyldehydroalanine, studied in extracts of rat kidney, liver, and hepatoma. Acetyl-nn-alanine, chloroacetyl-nn-phenylalanine, acetylglycine, and glycylglycine were also studied in kidn.ey digests, and the former two compounds compared, respectively, with acetyldehydroalanine and chloroacetyldehydrophenylalanine.