Endothelin-1 (ET-l), a 21-residue vasoactive peptide, is produced in vascular endothelial cells from the 38-residue inactive intermediate big endothelin-1 via a specific cleavage at Trp-Pl-Val-22. The protease that catalyzes the conversion, endothelin-converting enzyme (ECE), constitutes a potential regulatory she for the production of the active peptide. We report the identification of ECE-1, a novel membrane-bound neutral metalloprotease that is expressed abundantly in endothelial cells in vivo and is structurally related to neutral endopeptidase 24.11 and Kell blood group protein. When transfected intocultured cellsthat normally secrete only big ET-l, the EM-1 cDNA conferred the ablllty to secrete mature ET-l. In transfected cells, ECE-1 processes endogenously synthesized big ET-1 as well as exogenously supplied big ET-l, which intaracts with ECE-1 on the cell surface. ECE-1 may provide a target for pharmacological intervention to alter ET-1 production.

Vascular endothelial cells locally regulate the function of underlining smooth muscle cells by producing an array of vasoactive molecules such as nitric oxide and endothelin-1 (ET-l) in response to various stimuli (Vane and Batting, 1992). The release of these factors causes acute changes, chronic changes, or both in local vascular tone leading to alterations in local blood flow, and, in the long term, changes in smooth muscle proliferation, migration, and remodeling. ET-l, the first of the three endothelin isopeptides, is the most potent vasoconstrictor substance known (Yanagisawa, 1994; Yanagisawa et al., 1988). Vascular endothelium is the most abundant source of ET-1 in vivo. Endothelins act on two pharmacologically distinct subtypes of G protein-coupled receptors termed ETI, and ETe (Arai et al., 1990; Sakurai et al., 1990), which are expressed on a wide variety of vascular and nonvascular