Phosphoramidon-sensitive endothelin-converting enzyme in the cytosol of cultured bovine endothelial cells |
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Authors: | J Takada K Okada T Ikenaga K Matsuyama M Yano |
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Affiliation: | Central Research Laboratories, Banyu Pharmaceutical Co., Ltd., Tokyo, Japan. |
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Abstract: | Neutral metalloproteases with endothelin-1 (ET-1) converting activity were detected in membranous and cytosolic fractions of cultured endothelial cells (EC) from bovine carotid artery in a ratio of 5:1, respectively. The cytosolic enzyme specifically and quantitatively converts big ET-1 to ET-1 (Km = 10.7 microM), but does not convert big ET-3. Like the membranous enzyme, the cytosolic enzyme is only active at pH 6.5-7.5, and is competitively inhibited by phosphoramidon (Ki = 0.79 microM). The apparent molecular weight of the cytosolic enzyme is about 540 kD, which is 5-6 times greater than that of the membranous enzyme. These results indicate the presence of two types of phosphoramidon-sensitive neutral ET-converting enzyme in vascular EC. |
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