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Updated: Aug 16, 2026

A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
Published on: September 25, 2017
DNA methylase inhibition in vitro by N-methyl-N'-nitro-N-nitrosoguanidine
Abstract:
Several alkylating carcinogens were tested for their ability to inhibit DNA methylation in an in vitro assay. N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) was the only carcinogen studied that altered the methylase activity. It was further demonstrated that MNNG reacts with the DNA methylase protein and produces a mixed type of inhibition. Prevention of the MNNG effect by dithiothreitol and inhibition of the DNA methylase with iodoacetamide suggest that DNA methylase is a sulfhydryl-containing enzyme and that MNNG inactivates the enzyme by reacting with sulfhydryl groups.
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