Characterization of a dipeptidyl aminopeptidase from bovine adrenal medulla

Abstract: A dipeptidyl aminopeptidase was partially purified from a supernatant fraction of bovine adrenal medulla by gel filtration and anion‐exchange chromatography. From gel filtration, the apparent molecular weight of the enzyme was 68,100 and its pH optimum was 9.5. Its Km for hydrolysis of the synthetic substrate arginylarginine‐β‐naphthylamide was 5.5 × 10−6M. The enzyme was inhibited by metal ion chelating agents and thiol blocking agents. suggesting the requirement for both a metal ion and an active cysteine residue for its activity. Several peptides were cleaved by the dipeptidyl aminopeptidase involving the sequential removal of dipeptides from the N‐terminus. Biologically active peptides, such as leucine‐enkephalin, methionine‐enkephalin, and angiotensin II, were hydrolyzed by the dipeptidyl aminopeptidase although opioid peptides with a length greater than five amino acid residues were not susceptible to hydrolysis. Other peptides with a blocked N‐terminus (neurotensin, bombesin) or a proline residue adjacent to a potential cleavage site (substance P) were not hydrolyzed. The ability of this dipeptidyl aminopeptidase to degrade certain neuropeptides suggests that it could be involved in neuropeptide degradation. Copyright © 1988, Wiley Blackwell. All rights reserved