title: High-affinity binding of the converting enzyme inhibitor, ramiprilat, to isolated human glomeruli.
abstract: Evidence for effects of angiotensin converting enzyme (ACE) on isolated human glomeruli was provided using specific binding of tritium-labeled ramiprilat, a potent inhibitor of ACE. [3H]ramiprilat bound to isolated glomeruli, depending on time and temperature, displaying a KD of 3.8 nmol/L and a Bmax of 853 fmol/mg protein. Specific binding represented more than 90% of total binding. Dissociation occurred rapidly after dilution of the sample with incubation buffer or after addition of an excess of unlabeled inhibitor. Binding of [3H]ramiprilat was also inhibited by increasing concentrations of enalaprilat, another ACE inhibitor. ACE is a zinc-containing enzyme. Addition of EGTA to the assay, which chelates zinc ions, completely prevented binding. This was reversed by divalent Zn2+ and Ca2+ ions, but not by magnesium. Binding of [3H]ramiprilat to isolated glomeruli was maximal at pH 8, which also is optimal for ACE activity. The binding of [3H]ramiprilat to isolated human glomeruli is specific, and resembles the characteristics which have been found earlier for enzyme activity of ACE. Thus, binding of [3H]ramiprilat to isolated glomeruli can be assumed to be directed to ACE.
authors: Hoechst AG, Frankfurt, F.R.G.
authors: R H
authors: RH
authors: Becker
authors: U
authors: U
authors: Albus
authors: I
authors: I
authors: Kress
authors: W
authors: W
authors: Linz
authors: D
authors: D
authors: Vasmant
authors: F
authors: F
authors: Delarue
authors: J D
authors: JD
authors: Sraer
mesh_terms: D000328:Adult; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000378:metabolism*; D004656:Enalapril / Q000031:analogs & derivatives / Q000378:metabolism; D015773:Enalaprilat; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000378:metabolism*; D011485:Protein Binding; D011758:Pyrroles / Q000378:metabolism*; D017257:Ramipril / Q000031:analogs & derivatives*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D011758:Pyrroles; D004656:Enalapril; C052549:ramiprilat; D015773:Enalaprilat; D017257:Ramipril