Biochemical properties of the angiotensin-converting-like enzyme from the leech Theromyzon tessulatum

This article reports the evidence and the biochemical properties of an angiotens-inconverting (ACE)-like enzyme from head parts of the leech Theromyzon tessulatum. After solubilization from membranes with Triton X-114, the ACE-like enzyme was purified from the detergent-poor fraction. Four steps of purification including gel permeation and anion exchange chromatographies followed by a reversed-phase HPLC were needed. This poor glycosylated peptidyl dipeptidase (of ca. 120 kDa) hydrolyzes, at pH 8.4 and at 37 degrees C, the Phe(8)-His(9) bond of angiotensin I with a high catalytic activity (i.e., K-m: 830 mu M and K-cat/K-m: 153 s(-1) mM(-1)). The hydrolysis of angiotensin I is inhibitable at 80% by captopril (IC50 = 175 nM) and lisinopril (IC50 = 35 nM). This activity is strictly dependent on the presence of NaCl and is increased by Zn2+. This zinc metallopeptidase also attacks peptides that have in their sequence either Gly-His, Gly-Phe, or Phe-His bond [e.g., enkephalins (K-cat/K-m: 12 s(-1) mM(-1)) or bradykinin (K-cat/K-m: 2200 s(-1) mM(-1)]. Taken together, these arguments are consistent with an ACE-like activity implicated in metabolism of angiotensins and bradykinin in leeches.