Conversion of big endothelin-1 by membrane-bound metalloendopeptidase in cultured bovine endothelial cells.

We propose a candidate for the "putative" endothelin (ET) converting enzyme in the cultured endothelial cells (ECs) of bovine carotid artery. The enzyme is membrane-bound, soluble in 0.5% Triton X-100, and capable of converting human big ET-1 to ET-1 by a specific cleavage between Trp21 and Val22. The conversion reached 90% after a 5-hr incubation in the presence of DFP, PCMS and pepstatin A, but it was inhibited by EDTA, omicron-phenanthroline or phosphoramidon. The enzyme is very sensitive to pH, and active only between pH 6.6 and pH 7.6. Conversion of big ET-3 by this enzyme was only 1/9 that of big ET-1. From these results, ET-1 converting enzyme in the bovine EC is most likely to be a membrane-bound, neutral metalloendopeptidase, which is much less susceptible to big ET-3.