Oxidation of l‐Methionine by Bisperoxo(1,10‐phenanthroline)oxovanadate(V): A Mechanistic Study

In phosphate buffer media (pH 5.8–8.0), bisperoxo(1,10‐phenanthroline)oxovanadate(V) ( 1 ) oxidizes l ‐methionine to methionine sulfoxide. The stoichiometry of the reaction is 1:1. The reaction occurs in two subsequent first‐order steps. In the first step, one of the peroxo ligands of 1 gets substituted by l ‐methionine. The observed first‐order rate constants for both steps increase linearly with increasing H⁺] as well as with increasing l ‐methionine]. The EPR spectra prove that the reaction involves a cysteinyl radical‐type intermediate and that V^V gets reduced to a V^IV species.