Endothelin‐converting enzyme activity in human serum lipoprotein fraction

Abstract
Endothelin‐1 (ET‐1)‐converting enzyme (ECE) activity in the human serum lipoprotein fraction was studied using a sensitive enzyme immunoassay and reverse‐phase high performance liquid chromatography. The ECE activity of cleaving synthetic human big ET‐1 into ET‐1 by the serum lipoprotein fraction was about 14‐times greater than that by whole serum, and the activity was closely associated with lipoprotein itself. The lipoprotein ECE activity, which was optimal at pH 7.0, was inhibited by EDTA, o‐phenanthroline, phosphoramidon, thiorphan, phenylmethane‐sulfonyl fluoride and chymostatin, but not by cysteine or aspartic proteinase inhibitors, suggesting metalloproteinase‐ and chymotrypsin‐like properties. These results suggest that the serum lipoprotein ECE may be involved in the processing of big ET‐1 to ET‐1 in the circulatory system.

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