부산대학교 도서관

Endothelin‐converting‐enzyme‐1 (ECE‐1) belongs to the family of zinc metallopeptidases and is responsible for generating endothelin (ET) peptides from their inactive precursors the big endothelins (bigET). The enzyme is a type II integral membrane protein consisting of a short amino‐terminal cytosolic domain of 56 amino acids, a single transmembrane domain and a large putative extracellular domain containing the catalytic site. Recombinant and native ECE‐1 are expressed as a dimer. We have constructed a soluble form of ECE, named sECE*, by fusing the cleavable signal peptide of pro‐opiomelanocortin in frame to the complete extracellular domain of human ECE‐1. Stable expression of this construct in CHO cells resulted in the secretion of a fully active enzyme. In contrast to membrane‐bound ECE, sECE* was expressed as a monomer, highly glycosylated, as assessed by gel filtration and Western blot. However, recombinant sECE* converted bigET‐1 with similar specific activity as ECE‐1a. This activity was completely inhibited by phosphoramidon, but not by thiorphan and captopril. sECE* was active in a broad range of pH, showing an optimum of 6.6–6.8 for bigET‐1. Thus, the extracellular domain alone is sufficient for conferring full ECE‐1 activity, inhibitors recognition and substrate specificity.