An aminopeptidase activity in bovine pituitary secretory vesicles that cleaves the N-terminal arginine from beta-lipotropin60-65.
Secretory vesicles isolated from the neural and intermediate lobes of the bovine pituitary contained a membrane-bound aminopeptidase activity which cleaved arginine from beta-LPH60-65 (Arg-Tyr-Gly-Gly-Phe-Met) and Arg-MCA. Neither methionine enkephalin (Tyr-Gly-Gly-Phe-Met) nor Substance P, which has an N-terminal arginine followed by a proline, could serve as substrates for this aminopeptidase activity; nor could cathepsin B-like or chymotrypsin-like enzyme activities be detected in the vesicle preparations. Maximal enzyme activity was at pH 6.0, and the activity was inhibited by EDTA, stimulated by Co2+ and Zn2+, but was unaffected by leupeptin, pepstatin A, phenylmethylsulfonyl fluoride and p-chloromercuribenzenesulfonate, suggesting that the enzyme is a metalloaminopeptidase. The presence of this aminopeptidase activity in secretory vesicles suggests that it may be involved in peptide prohormone processing.
D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000378:metabolism; D002413:Cations, Divalent; D002417:Cattle; D003594:Cytoplasmic Granules / Q000201:enzymology*; D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009928:Organ Specificity; D010446:Peptide Fragments / Q000378:metabolism*; D010902:Pituitary Gland / Q000201:enzymology*; D010904:Pituitary Gland, Posterior / Q000201:enzymology; D011480:Protease Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity; D008083:beta-Lipotropin / Q000378:metabolism*
D002413:Cations, Divalent; D010446:Peptide Fragments; D011480:Protease Inhibitors; C043031:beta-lipotropin (60-65); D008083:beta-Lipotropin; D001120:Arginine; D004492:Edetic Acid; D000626:Aminopeptidases