title: Inhibitor binding assay of rat serum angiotensin converting enzyme.
abstract: Based on a specific binding of labelled inhibitor to the enzyme active centre, a new principle of enzyme assay, inhibitor binding assay (IBA), was developed and applied to measurement of rat serum angiotensin converting enzyme (ACE). Serum diluted 1:50 was incubated with 125I-labelled ACE inhibitor, 351A, at pH 7.0, 37 degrees C, for 2 h. Inhibitor bound to ACE was separated with coated charcoal and results were calculated from a standard curve. The advantages offered by the novel inhibitor binding assay include simplicity, specificity, absence of interference by other enzymes or immunological cross-reactions, and great sensitivity enabling measurement of ACE in concentrations less than 0.1 units/ml. This principle of enzyme assay will not only have potential new applications for research involving ACE but may also be extended to other enzymes.
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors; D000818:Animals; D004151:Dipeptides / Q000494:pharmacology; D005260:Female; D007457:Iodine Radioisotopes; D008722:Methods; D007703:Peptidyl-Dipeptidase A / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D004151:Dipeptides; D007457:Iodine Radioisotopes; C042037:L-proline, N2-((1S)-1-carboxy-3-phenylpropyl)-N6-((4-hydroxyphenyl)iminomethyl)-L-lysyl-; D007703:Peptidyl-Dipeptidase A