Identification and characterization of two isoforms of an endothelin‐converting enzyme‐1

Abstract
We report the cloning and sequencing of 5′-terminal region of a β form of rat ECE-1 cDNA which is different only in its N-terminal amino-acid sequence to the cDNA we have cloned previously (α form [K. Shimada et al. (1994) J. Biol. Chem. 269, 18275–18278]). No significant difference was found in the specific activity and substrate specificity between the two isoforms. The expression level of ECE-1α mRNA was higher than that of ECE-1β in various rat cells and tissues, suggesting that the physiologically important isoform is ECE-1α. The present findings verified the presence of two forms of ECE-1 over many species, which are created probably through alternative splicing.