The specificity of some pig and human pepsins towards synthetic peptide substrates

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Abstract
The peptidase activities of pig pepsins A and C and human pepsin and gastricsin were compared. The peptides studied had the general formual A-Leu-Val-His-B. Hydrolysis at 37.degree. C and pH 2.07 occurred at the amino side of the leucine residue for all the enzymes and all the peptides. When A was Ac-Ala the peptides were hydrolyzed under these conditions slowly by pig pepsin C only. Pig pepsin A and human pepsin were unable to hydrolyse the tyrosine-containing peptides under the conditions tested. Gastricsin (human pepsin C) had about 1/3 of the activity of pig pepsin C with these substrates. The increase in the rate of hydrolysis caused by the extension of the chain by a single alanine residue was most marked for pig pepsin A and human pepsin.