Presence and biochemical properties of a molluscan invertebrate angiotensin-converting enzyme

A soluble 65582.9 Da (in MALDI-TOF) angiotensin converting (ACE)-like enzyme has been purified by a captopril-Sepharose affinity column chromatography from the mollusk Mytilus edulis. This glycosylated peptidyl dipeptidase, with an N-terminal sequence of LDPELSPGCFVANQAGGQLF, hydrolyses the Phe8-His9 bond (at pH 8.4 and 37 degrees C) of angiotensin I with a high catalytic activity i.e. K-m: 168 mu M and K-cat/K-m: 262 s(-1) mM(-1). The hydrolysis of angiotensin I is inhibited by the specific ACE inhibitors captopril and lisonopril (Ic(50) = 50 nM). This activity is increased by Cl- (optimal Cl- concentration 400 mM) and by Zn2+. This zinc metallopeptidase also attacks peptides having a Gly-His, Gly-Phe or a Phe-His bond in their sequence e.g. leucine-enkephalin (K-cat/K-m: 1200 s(-1) mM(-1)) or bradykinin (K-cat/K-m: 2500 s(-1) mM(-1)). Mytilus ACE displays properties of the C-domain of human ACE, indicating a high degree of conservation during evolution. These results are consistent with an ACE activity implicated in metabolism of several neuropeptides in mollusks. (C) 1997 Elsevier B.V.