Identification and characterization of endothelin converting enzyme in rat lung

• Published in: Japanese Journal of Pharmacology 1992, Vol.58 (suppl.1), p.114-114
• Main Authors: Takaoka, Masanori, Fujino, Katsuhiro, Miki, Keiko, Matsumura, Yasuo, Morimoto, Shiro
• Format: Article
• Language: English
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1016/S0021-5198(19)48840-9

The present study was designed to identify and characterize a neutral proteinase with endothelin (ET) converting activity in the lung, a tissue known to contain a high level of ET-1 and to express its mRNA. Incubation of synthetic porcine big ET-1 with either the cytosolic or membrane fraction prepared from rat lung, resulted in an increase in immunoreactive-ET. The apparent ratio of ET converting activities in the cytosolic and membrane fractions was 1：4, respectively. The membrane fraction showed a 7.6-fold higher specific activity than the cytosolic fraction. The membrane bound proteinase was solubilized by 0.5% CHAPS with an increase in specific activity, and then was characterized. The solubilized proteinase was capable of converting big ET-1 to ET-1 with an optimum pH of 6.5, and the conversion was dose-dependently suppressed by phosphoramidon (IC_50 =0.5 μM). The molecular mass of the proteinase was estimated to be about 500 kD by gel filtration in the presence of 0.5% CHAPS. These results indicate that rat lung contains a phosphoramidon-sensitive neutral proteinase catalyzing conversion of big ET-1 to ET-1 . The proteinase may be involved in the biosynthetic pathway of ET-1 in the lung and/or the conversion of circulating big ET-1.