The role of proline in the proteolytic regulation of biologically active peptides

Specificity studies of the enzymatic hydrolysis of proline-containing peptides give further evidence of the unique nature of the Xaa-Pro bond and indicate its role in the limited proteolysis as a structural element protecting the N-terminal chain end. A sensitive, highly specific fluorogenic assay was developed for aminopeptidase P [EC 3.4.11.9], that specifically cleaves N-terminal Xaa-Pro bonds. Examples of polypeptides with known N-terminal Xaa-Pro sequences are listed and the influence of proline on the proteolytic processing of polypeptide precursors is discussed.