Is there a tripeptidyl peptidase in the renal brush-border membrane?
A recent claim that the renal brush border contains a tripeptidyl peptidase [Andersen & McDonald (1987) Am. J. Physiol. 253, F649-F655] was examined. In a fluorescent assay, the hydrolysis of Gly-Pro-Met-2-naphthylamide (-NH-Nap) and Gly-Pro-Leu-NH-Nap by pig kidney microvilli was strongly inhibited by amastatin or di-isopropyl phosphorofluoridate (inhibitors of aminopeptidases and dipeptidyl peptidase IV). The products formed were shown to be Gly-Pro and Met-NH-Nap (or Leu-NH-Nap) and free 2-naphthylamine. Specific antibodies to pig and rat aminopeptidase N abolished the apparent tripeptidyl peptidase activity. We conclude that these substrates are hydrolysed by the sequential attack of dipeptidyl peptidase IV and aminopeptidase N and that pig and rat brush borders lack a detectable tripeptidyl peptidase.
Kenny
A J
AJ
Department of Biochemistry, University of Leeds, U.K.
Ingram
J
J
D000626:Aminopeptidases / Q000276:immunology; D000818:Animals; D000906:Antibodies; D002852:Chromatography, Ion Exchange; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D010450:Endopeptidases / Q000276:immunology / Q000378:metabolism*; D006868:Hydrolysis; D007672:Kidney Cortex / Q000201:enzymology*; D008871:Microvilli / Q000201:enzymology; D009842:Oligopeptides / Q000378:metabolism; D011480:Protease Inhibitors; D013552:Swine
D000906:Antibodies; D009842:Oligopeptides; D011480:Protease Inhibitors; C057836:glycyl-prolyl-methionyl-2-naphthylamide; C057835:glycyl-prolyl-leucyl-2-naphthylamide; D010450:Endopeptidases; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases