ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
An aminopeptidase with specificity directed toward peptides with acidic N-terminal amino acid residues has been isolated from mouse brain cytosol. Purification by ion-exchange chromatography and gel filtration resulted in an enzyme that hydrolyzed aspartyl-phenylala-nine methyl ester at a rate of 13.2 μu,mol/min/mg protein at pH 7.5, an increase in specific activity of 1000-fold over that of brain homogenate. Its apparent molecular weight, determined by gel filtration, is ˜450,000. Dipeptides with N-terminal aspartyl residues are cleaved preferentially to glutamic-containing analogs, and a neutral amino acid (or histidine) is necessary in the adjacent position. For pep-tides of the form aspartyl-X, relative activity was 100, 81, 71, 66, 19, or 0, where X was alanine, serine, leucine, phenylalanine, histidine, or proline, respectively. Tripep-tides were more rapidly hydrolyzed than dipeptides; however, activity tended to decline with increasing chain length. The acidic aminopeptidase can account for almost all of the activity of brain cytosol toward the N-terminal aspartyl residue of angiotensin II, aspartyl-phenylalanine methyl ester or aspartyl-alanine, and the N-terminal glu-tamyl residue of adrenocorticotropin(5-10). The enzyme was unaffected by bestatin or amastatin. It was inhibited by o-phenanthroline and EDTA. The latter effect could be reversed completely by Zn2+ and partially by Mn2+ or Mg2+; Co2+ and Fe2+ had no effect; Ca2+ was inhibitory. These properties distinguish the brain acidic aminopeptidase from aminopeptidase A isolated from human serum or pig kidney and the aspartyl aminopeptidase of dog kidney.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1983.tb08148.x
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