Enkephalin degrading enzymes are present in the electric organ of Torpedo californica

Abstract

Two proteolytic activities that degrade [Leu⁵]enkephalin were found in Torpedo californica electric organ. One is a soluble aminopeptidase that degrades enkephalin at the Tyr¹—Gly² peptide bond, and the second is an endopeptidase that degrades enkephalin at the Gly³—Phe⁴ peptide bond. The aminopeptidase is inhibited by low concentrations of puromycin and bestatin. More than 60% of the endopeptidase is associated with the particulate fraction and is almost completely inhibited by low concentrations of captopril (SQ 14225) or SQ 20881 (potent inhibitors of angiotensin converting enzyme). Thiorphan and phoshoramidon (potent enkephalinase inhibitors) are much less effective. The pattern of cleavage and inhibition of the particulate endopeptidase thus resembles that of angiotensin converting enzyme.