Some Molecular and Inhibitory Specifications of a Dipeptidyl Carboxypeptidase from the Polychaete Neanthes virens Resembling Angiotensin I Converting Enzyme

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Dipeptidyl carboxypeptidase (DCP) from the polychaete Neanthes virens, resembling mammalian angiotensin I converting enzyme (ACE), was studied to discover some of its molecular and inhibitory properties, as the first evidence of these in a marine invertebrate. Amino acid and carbohydrate contents were analyzed. The N-terminal amino acid sequence of N. virens DCP was (NH_2) D-E-E-A-G-R-Q-W-L-A-E-Y-D-L-R-N-Q-T-V-L-. Peptide maps of N. virens DCP from lysyl endopeptidase digestion were different from rabbit p-ACE. The far-ultraviolet circular dichroic spectra of N. virens DCP indicated that the secondary structure of this enzyme seemed to be an α-helical structure and was similar to that of rabbit p-ACE, but the nearultraviolet circular dichroic spectra of N. virens DCP indicated that the aromatic amino acid residue circumambience of this enzyme was different from rabbit p-ACE. The effects of several reagents for chemical modification of amino acids on the activity of N. virens DCP were tested. Arg, Tyr, Glu, and/or Asp, His, Trp, and Met caused loss of the activity. In addition, the IC_<50> and K_1 values for a well-known ACE inhibitor, Val-Tyr, which was a competitive inhibitor of N. virens DCP, were 263 and 20μM, respectively. These results suggested that N. virens DCP is different from mammalian ACE in the molecular and inhibitory properties, although the same substrate specificity was demonstrated in a previous paper.
2000-10-23