Abstract
Abstract Angiotensin-converting enzyme was found in rat lung predominantly in association with membranous subcellular particles. The converting enzyme was solubilized from a particulate fraction of rat lung that sedimented between 775 and 54,000 x g with sodium deoxycholate and was subsequently purified with DEAE-cellulose and Sephadex G-200 chromatography. The fraction with converting enzyme activity obtained from Sephadex G-200 chromatography had an estimated molecular weight of 270,000 as observed by gel filtration. Analytical disc gel electrophoresis of this preparation showed a single band. The specific converting enzyme activity of the purified preparation was 17.6 µmoles per min per mg with hippurylhistidylleucine as substrate and 1.8 µmoles per min per mg with angiotensin 1 as substrate. This represented a greater than 100-fold purification of the activity of subcellular particles. Sodium chloride was required for activation of the enzyme, and it was inhibited by EDTA, bradykinin potentiating factor-nonapeptide, and angiotensin 2, but not by histidylleucine. The purified preparation was free of carboxypeptidase activity on angiotensin 1. The distribution of converting enzyme activity in subcellular particles from rat lung paralleled that of 5'-AMPase activity which has been associated with pinocytotic vesicles of endothelial membranes. Little or no converting enzyme activity was present in particles obtained from lung lavage.
Highlights
Angiotensin-converting enzyme was found in rat lung predominantly in association with membranous subcellular particles
Sodium chloride was required for activation of the enzyme, and it was inhibited by EDTA, bradykinin potentiating factor-nonapeptide, and angiotensin 2, but not by histidylleucine
It was found that the predominant amount of converting enzyme in the rat lung is associated with structural elements, probably of membranous origirl, and that the enzyme can be solubilized from these particles ant1 highly purified by a combination of DEAEcellulose and Scphadex G-200 chromatography
Summary
Angiotensin-converting enzyme was found in rat lung predominantly in association with membranous subcellular particles. It was found that the predominant amount of converting enzyme in the rat lung is associated with structural elements, probably of membranous origirl, and that the enzyme can be solubilized from these particles ant highly purified by a combination of DEAEcellulose and Scphadex G-200 chromatography. It n-as found that the distribut,ioll of converting enzyme activity corresponded closely to that of 5’-AMPase activity in fractionated subcellular particles, and that no converting enzyme activity coultl be recovered from cells and particles obtained by lung lavage. The thiracic cavity was opened and the pulmonary artery was cannulated with a catheter inserted through the right atrium
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