Direct Alkylation of Deoxyguanosine by Azaserine Leads to <i>O</i>⁶-Carboxymethyldeoxyguanosine

The O6-alkylguanosine adduct O6-carboxymethyldeoxyguanosine (O6-CMdG) has been detected at elevated levels in blood and tissue samples from colorectal cancer patients healthy volunteers after consuming red meat. diazo compound l-azaserine leads to the formation of O6-CMdG as well corresponding methyl O6-methyldeoxyguanosine (O6-MedG) cells is therefore wide use a chemical probe cellular studies concerning DNA damage mutation. However, there remain knowledge gaps basis by l-azaserine. To characterize l-azaserine, we carried out combination enzymatic stability reactivity supported liquid chromatography tandem mass spectrometry for simultaneous quantification O6-MedG. We found that stable under physiological alkaline conditions active biological matrices but undergoes acid-catalyzed hydrolysis. show, first time, reacts directly with guanosine (dG) oligonucleotides form an O6-serine-CMdG (O6-Ser-CMdG) adduct. Moreover, characterizing reaction dG demonstrate O6-Ser-CMdG forms intermediate spontaneously decomposes O6-CMdG. Finally, quantified O6-MedG human cell line exposed maximal 48 h. findings this work elucidate how deoxyguanosine support its N-nitroso exposure carcinogenesis research, particularly identification pathways factors promote formation.