The Angiotensin 1 Converting Enzyme of the Lung.
Abstract : Angiotensin 1 coverting enzyme or kininase 2 (dipeptide hydrolased(DH) was purified from hog lung. The preparation was homogeneous in disc gel electrophoresis. Lung DH inactivated bradykinin and converted angiotensin 1 to angiotensin 2. DH cleaved dipeptides in vitro from the C-terminal end of various substrates including angiotensin 1, bradykinin, B-chain of insulin and shorter peptides, which were employed as substrates in spectrophotometric experiments. Several peptides including glutathione, insulin and the synthetic peptides SQ 20881 and peptide C inhibited both plasma and lung DH. The latter inhibitors were inactive against carboxypeptidase N or kininase 1. DH cleaved both bradykinin and angiotensin 1 as determined by bio-assay or radio-immunoassay. DH was also studied in the rat lung. During passage through the pulmonary circulation half of the angiotensin I was converted to angiotensin 2 by the liberation of His-Leu; Gly-Gly was cleaved from the dansly substrate The activity of DH in the perfused lung of hypertensive rats was normal. Inhibitors such as insulin or SQ 20881 also blocked the action of DH in lung perfusion experiments. (Author)