title: 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.
mesh_terms: D000818:Animals; D004247:DNA / Q000378:metabolism; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors*; D004229:Dithiothreitol / Q000494:pharmacology; D066298:In Vitro Techniques; D007460:Iodoacetamide / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008780:Methyltransferases / Q000037:antagonists & inhibitors*; D051381:Rats; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D013438:Sulfhydryl Compounds; D008769:Methylnitronitrosoguanidine; D004247:DNA; D008780:Methyltransferases; D004248:DNA (Cytosine-5-)-Methyltransferases; D004229:Dithiothreitol; D007460:Iodoacetamide