Endothelin-converting enzyme 1 (ECE1) is a type II membrane-bound zinc metalloprotease. It cleaves the longer form of endothelin (EDN1(53-90), also known as Big ET-1, by an unusual selective hydrolysis of Trp21-Val22, producing EDN1. ECE1 exhibits maximal activity at pH 7.0. It comprises a short cytoplasmic N-terminal tail, a membrane-spanning region, and a large extracellular domain containing a zinc-binding motif essential for enzymatic activity (Schweizer et al. 1997, Valdenaire et al.1999, Jeng et al. 2002).