Characterization of a dipeptidyl aminopeptidase from bovine adrenal medulla.
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-beta-naphthylamide was 5.5 X 10(-6) M. 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.
Kecorius
E
E
Department of Biochemistry, University of Melbourne, Parkville, Victoria, Australia.
Small
D H
DH
Livett
B G
BG
D000313:Adrenal Medulla / Q000201:enzymology* / Q000648:ultrastructure; D000818:Animals; D002413:Cations, Divalent; D002417:Cattle; D002458:Cell Fractionation; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003035:Cobalt / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009479:Neuropeptides / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D013347:Subcellular Fractions / Q000201:enzymology; D015032:Zinc / Q000494:pharmacology
D002413:Cations, Divalent; D009479:Neuropeptides; D011480:Protease Inhibitors; D003035:Cobalt; D003300:Copper; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D015032:Zinc