Peroxidative metabolism of benzidine derivatives by Salmonella typhimurium.
Benzidine and several derivatives are activated to mutagenic species in an H2O2-dependent Ames test system. Optical and electron paramagnetic resonance (EPR) spectroscopy are employed in studies of the H2O2-dependent oxidation of benzidine and 3,5,3',5'-tetramethylbenzidine (TMB) catalyzed by intact bacteria, and provide direct evidence for peroxidase activity in Salmonella typhimurium. The acetylase-proficient Ames tester strain TA98 and its acetylase-deficient derivative TA98/1,8-DNP6 are equally responsive to H2O2-dependent mutagenicity; enzymatic acetylation appears not to be involved in activation of benzidine, in this system. The H2O2-dependent mutagenicity of benzidine and oxidation of TMB are observed when the assays are carried out in acetate buffer (pH 5.5), but not in 2-[N-morpholino]ethane sulfonic acid (MES) buffer, at the same pH. This difference is interpreted in terms of the effects of these buffers on the intracellular pH of the bacteria. The H2O2-dependent mutagenicity of several benzidine congeners is also described.
de France
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Guelph-Waterloo Centre for Graduate Work in Chemistry, Dept. of Chemistry and Biochemistry, University of Guelph, Ontario, Canada.
Josephy
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D001560:Benzidines / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D009152:Mutagenicity Tests; D010084:Oxidation-Reduction; D012486:Salmonella typhimurium / Q000378:metabolism*
D001560:Benzidines; C021758:3,3',5,5'-tetramethylbenzidine; D006861:Hydrogen Peroxide