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CHARACTERIZATION OF ANGIOTENSIN CONVERTING ENZYME FROM RAT TISSUE BY RADIO‐INHIBITOR BINDING STUDIES
Author(s) -
Jackson Bruce,
Cubela Rose,
Johnston Colin I.
Publication year - 1986
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1986.tb02397.x
Subject(s) - kidney , ace inhibitor , angiotensin converting enzyme , enzyme , lung , dissociation constant , medicine , binding site , endocrinology , chemistry , aorta , enzyme inhibitor , biochemistry , biology , receptor , blood pressure
SUMMARY 1. Angiotensin converting enzyme (ACE) derived from rat lung, aorta, epididymus, brain, kidney and plasma was characterized by radio‐inhibitor ( 125 I‐MK351A) binding studies. Under optimal binding conditions at equilibrium 125 I‐MK351A bound to ACE was displaced from ACE in a concentration related manner by unlabelled MK351A. 2. MK351A binding site concentration for each tissue and equilibrium dissociation constant (K D ) was estimated by Scatchard analysis of binding data. Binding sites/mg protein was greatest in lung and least in brain. The K D for kidney ACE was significantly higher than that of lung, aorta, epididymus or brain ACE ( P <0.005; t ‐test, d.f. = 10). 3. 125 I‐MK351A bound to ACE prepared from lung and kidney was displaced in a concentration dependent manner by SQ20881, SQ14225, MK422, and Ro31–3113–000. Concentration of ACE inhibitor required to displace 50% of bound 125 I‐MK351A (DD 50 ) was consistently higher for kidney‐derived ACE than lung‐derived ACE. 4. The differences in radio‐inhibitor binding characteristics of ACE from different rat tissues suggests that the enzyme active site may not be identical in all organs.