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  • Title: Reductive metabolism of 1-nitropyrene accompanies deamination of cytosine.
    Author: Malia SA, Basu AK.
    Journal: Chem Res Toxicol; 1994; 7(6):823-8. PubMed ID: 7696538.
    Abstract:
    1-Nitropyrene (1-NP), a common environmental pollutant, is a mutagen and tumorigen. Nitroreduction is a major pathway by which 1-NP is metabolized. In order to study the mutational specificity of reductively activated 1-NP, single-stranded M13mp18 DNA was treated with tritium-labeled 1-nitrosopyrene in the presence of ascorbic acid to generate N-hydroxy-1-aminopyrene in situ. HPLC analysis of the treated DNA, following enzymatic digestion, showed that > 95% of tritium was located in one major adduct, N-(deoxyguanosin-8-yl)-1-aminopyrene. Transfection of these adducted M13 DNA in Escherichia coli indicated a dose-dependent reduction in viability with concomitant enhancement in mutagenesis in the lacZ gene fragment. Without SOS functions, the major type of mutation was C-->T transition (48%). Further studies have shown that cytosine deamination occurred during ascorbic acid-induced nitroreduction, which was likely responsible for the C-->T transitions. Deamination of cytosine alco occurred at a significant frequency when nitroreduction of either 1-NP or 1-nitrosopyrene was catalyzed by xanthine oxidase, a mammalian nitroreductase.
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