ANGIOTENSIN‐CONVERTING ENZYME (ACE) MEASUREMENT IN HUMAN SERUM USING RADIOINHIBITOR LIGAND BINDING

Publisher Website
Google Scholar
Abstract
MK315A, a tyrosyl analogue of enalaprilic acid (MK422) is a potent inhibitor of angiotensin-converting enzyme (ACE). MK351A was radioiodinated with 125I and used to develop a radioinhibitor binding assay for human serum ACE. 125I MK351A associated rapidly and reversibly with human serum ACE (T½ = ½ h). Bound 125I MK351A was displaced by an excess of cold MK351A, to give non-specific binding of <1%. Scatchard analysis of binding was linear (r= -099, n=6, p<0001), indicating a single class of binding site. ACE was estimated in serum from normal patients and patients with sarcoid by the radio inhibitor binding assay and by enzyme kinetic assay using Hip-His-Leu as substrate. The two methods for ACE estimation correlated closely (r = 087, n=82, p<0001). The radioinhibitor binding assay for human serum ACE is a simple, sensitive and specific assay which utilizes novel assay methodology.