OXIDATION OF AZO DYES BY PEROXIDASE - ADDITIONAL EVIDENCE OF A ONE-ELECTRON MECHANISM OF OXIDATION OF DIMETHYLAMINOAZOBENZENE AND SUDAN-I (SOLVENT-YELLOW-14)

In the presence of hydrogen peroxide, peroxidase oxidized aminoazo dye s, the non-aminoazo dye 1-phenylazo-2-hydroxynaphthalene (Sudan I, Sol vent Yellow 14), and its C-hydroxy derivatives. The oxidation of azo d yes is a pi-I-dependent reaction; while slightly acidic conditions are optimal for the aminoazo dyes, a basic pH suits better for Sudan I an d its hydroxy derivatives. The oxidation of the carcinogenic Sudan I a nd dimethylaminoazobenzene catalyzed by peroxidase was investigated in detail. Oxygen consumption was not observed in incubations of peroxid ase, azo dyes and hydrogen peroxide. However, oxygen uptake was observ ed after the addition of glutathione, which indicates that free radica l metabolites of these compounds are formed by peroxidase. The results suggest that peroxidase metabolizes Sudan I and dimethylaminoazobenze ne through a one-electron oxidation mechanism, giving rise to free rad icals. Three of the products of Sudan I oxidation by peroxidase with a hitherto unknown structure were characterized partly by UV/VIS and ma ss spectroscopy.