ESR studies on the oxidation of N,N-dimethyl-p-anisidine and its analogues catalyzed by myeloperoxidase.
N,N-Dimethyl-p-anisidine (DMA) was used as a substrate to differentiate between the direct, or chloride-independent, and the indirect, or chloride-dependent, pathways characteristic of myeloperoxidase (donor: hydrogen-peroxide oxidoreductase, EC 1.11.1.7). The chemical oxidation by sodium hypochlorite and the horseradish peroxidase-catalyzed oxidation by H2O2 were also investigated for a comparison. The chemical oxidation of DMA by NaOCl (DMA/NaOCl = 1) gave the p-N,N-dimethylaminophenoxy radical at pH 5 and 7. p-Benzoquinone and formaldehyde were determined as stable end-products. On the other hand, the cation radical of DMA was detected and p-benzoquinone was not obtained in the horseradish peroxidase-H2O2-Cl- system. In the presence of Cl- the myeloperoxidase-catalyzed oxidation at pH 5 gave nearly the same result as did the oxidation by NaOCl, whereas in the absence of Cl- the result of the oxidation was similar to that of the horseradish peroxidase-catalyzed oxidation, except for a low yield of formaldehyde formation, which was ascribed to the decomposition of H2O2 by the catalase activity of myeloperoxidase. Although the myeloperoxidase-catalyzed oxidation of DMA at pH 7 in the presence of Cl- gave only the cation radical of DMA, a fairly large amount of p-benzoquinone was obtained as a product. This result indicates that the indirect chloride-dependent oxidation is also operating at pH 7. The reaction mechanism for the myeloperoxidase-catalyzed oxidation of DMA is proposed.
D000814:Aniline Compounds / Q000378:metabolism*; D000818:Animals; D001853:Bone Marrow / Q000201:enzymology; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D007700:Kinetics; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism*; D051381:Rats; D013379:Substrate Specificity
D000814:Aniline Compounds; C050795:N,N-dimethyl-4-anisidine; D009195:Peroxidase