Endothelin-1 (ET-1) is the predominant isoform of the endothelins, a family of endothelium-derived vasoconstrictor peptides. Endothelin-1 is expressed as a 212-aa precursor (preproendothelin-1) that is sequentially cleaved into 2 chains: Endothelin-1 (21 aa) and Big Endothelin-1 (38 aa). Big endothelin-1 is cleaved to yield endothelin-1 via the activity of an endothelin-converting enzyme (ECE), chymases and non-ECE metalloproteases. ET-1 exerts various biological effects, including vasoconstriction and the stimulation of cell proliferation in tissues via ET receptors A and B. Human: H-Cys-Ser-Cys-Ser-Ser-Leu-Met-Asp-Lys-Glu-Cys-Val-Tyr-Phe-Cys-His-Leu-Asp-Ile-Ile-Trp-OH (Cys1-Cys15, Cys3-Cys11) or H-CSCSSLMDKECVYFCHLDIIW-OH (Cys1-Cys15, Cys3-Cys11)