Peroxidase oxidizes N-nitrosomethylaniline to ultimate carcinogens(s) binding to DNA and transfer RNA in vitro.

Carcinogenic N-nitrosomethylaniline is oxidized in vitro by horseradish peroxidase in the presence of H2O2 to ultimate carcinogens, which bind to DNA and transfer RNA (tRNA). tRNA is more accessible for modification by the activated carcinogen studied. The modification of nucleic acid by N-nitrosomethylaniline metabolite(s) formed by peroxidase is inhibited by some compounds of physiological importance (ascorbate, glutathine) and by radical trapping agents (nitrosobenzene, methyl viologen). 32P-postlabeling assay of DNA and tRNA modified by N-nitrosomethylaniline activated by peroxidase shows covalent adduct formation with nucleic acids. The role of peroxidases in the activation of N-nitrosamines leading to organ and/or cell specificity of these carcinogens is discussed.