A novel mammalian high-molecular-weight aminopeptidase.
Studies with the human lymphoma U937 cell line revealed the presence of two soluble aminopeptidase activities. Using specific antisera one of these was identified as the puromycin-specific aminopeptidase, while the other appeared to be a novel approximately 200-kDa activity. The kinetic properties of this high-molecular-weight aminopeptidase, referred to as Ap200, were similar to those of the puromycin-sensitive aminopeptidase, but showed quantitative differences. Ap200 is relatively insensitive to inhibition by both puromycin, K(i) = 27 microM, and bestatin, K(i) = 1.6 microM. Among the synthetic beta-naphthylamides, Ap200 is more specific for alanine-beta-naphthylamide compared to the puromycin-sensitive aminopeptidase. Similarly, this enzyme cleaves a more limited number of physiological peptides exhibiting a preference for the enkephalins. Ammonium sulfate, but not sodium chloride at the same ionic strength, was able to dissociate the high-molecular-weight aminopeptidase to a approximately 100-kDa active form. The high-molecular-weight aminopeptidase is found as a low abundant protein in a number of tissues including intestine, kidney, liver, lung, muscle, spleen, and testes, but could not be detected in adrenal, heart, or brain. Thus, it has a tissue distribution which differs from the puromycin-sensitive aminopeptidase.
Erbeznik
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Department of Biochemistry, University of Kentucky, Lexington 40536-0084, USA.
Hersh
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D000409:Alanine / Q000031:analogs & derivatives / Q000378:metabolism; D000577:Amides / Q000378:metabolism; D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000201:enzymology; D002850:Chromatography, Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D007930:Leucine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D008223:Lymphoma; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011691:Puromycin / Q000378:metabolism / Q000494:pharmacology; D013154:Spleen / Q000201:enzymology; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
D000577:Amides; D004791:Enzyme Inhibitors; D007106:Immune Sera; D007527:Isoenzymes; D010455:Peptides; C028104:alanine-beta-naphthylamide; D011691:Puromycin; C029772:arginine beta-naphthylamide; D001120:Arginine; D000626:Aminopeptidases; D007930:Leucine; C012211:ubenimex; D000409:Alanine