A COMPARISON OF THE N-TERMINAL SEQUENCE OF THE LEECH THEROMYZON TESSULATUM ANGIOTENSIN CONVERTING-LIKE ENZYME WITH FORMS OF VERTEBRATE ANGIOTENSIN-CONVERTING ENZYMES

This paper reports the purification of an angiotensin-converting like enzyme (ACE) of ca. 120kDa from extracts of head membranes of the leech Theromyzon tessulatum. After solubilization with Triton X-114, the ACE-like enzyme contained in the detergent-poor fraction was separated using five steps of purification including gel permeation and anion exchange chromatographies followed by reverse-phase HPLC. The first 23 amino acid residues of the N-terminal part (GLDPELSPGCFSADEAGAQLFAE) of the purified S-pyridylethylated leech ACE established by automated Edman degradation revealed ca. 87% sequence identity with the N-terminal sequence of the guinea pig ACE. This enzyme cleaves the hyppuryl-His-Leu substrate with a specific activity of 5600 nmol hyppurate min(-1) mg protein(-1) Hydrolysis of this substrate by ACE-like enzyme is inhibited at 80% by 10 mu M captopril or 10 mu M lisinopril (IC50 of 200 nM and 50 nM, respectively). This enzyme is close in sequence and in activity to single domain vertebrate ACE. This is the first N-terminal sequence of an ACE-like enzyme determined in invertebrates.