Angiotensin-cleaving catalysts: conversion of N-terminal aspartate to pyruvate through oxidative decarboxylation catalyzed by Co(III)cyclen.

To provide a firm basis for the new paradigm of drug discovery based on peptide-cleaving catalysts, oligopeptide-cleaving catalysts were searched for by using human angiotensin I (Ang-I) and angiotensin II (Ang-II) as the substrates. Catalyst candidates containing the Co(III) complex of cyclen as the catalytic center were prepared by multicomponent condensation reactions. From two types of chemical libraries containing about 3,600 catalyst candidates, two compounds [SS-Co(III)X and S-Co(III)Y] were selected as the most active catalysts. On incubation with SS-Co(III)X and S-Co(III)Y, both Ang-I and Ang-II were cleaved by oxidative decarboxylation instead of peptide hydrolysis: the N-terminal Asp residues of Ang-I and Ang-II were converted to pyruvate residues. Catalysts for oxidative decarboxylation of the N-terminal Asp residue contained in an oligopeptide are unprecedented in both biological and chemical systems. Detailed kinetics analysis suggested that Ang-I and Ang-II can be cleaved with half-lives much less than 1 h if the structures of the chelating ligands of the catalysts are further improved. The results indicated that the concept of the peptide-cleaving catalysts can be expanded to include oligopeptides as the targets and nonhydrolytic reactions as the means for cleavage.