N2-methyl-8-oxoguanine: a tRNA urinary metabolite--role of xanthine oxidase.
DNA damage produces a series of oxidation products including 8-oxo-2'-deoxyguanosine and 8-oxoguanine, whose urinary excretion have been used to estimate in vivo oxidative injury. A monoclonal antibody to 8-oxoguanine was used to measure these adducts in urine taken from ill infants. In the process of this investigation we observed a large chromatographic peak that did not correspond to any of the known 8-oxoguanine adducts. A combination of liquid chromatography with electrochemical detection and gas chromatography/mass spectrometry allowed isolation and identification of the previously undescribed oxidation product, N2-methyl-8-oxoguanine. The excretion of this compound is increased in ill and growing infants but is also found in the urine of adult rats and humans. Experiments with allopurinol, a xanthine oxidase inhibitor, show that in humans, N2-methyl-8-oxoguanine is formed from the tRNA modified base N2-methylguanine. This is in contrast to the nonmethylated bases, which are converted to 8-oxo derivatives as a result of oxidative damage to nucleic acids and do not appear to be substrates for xanthine oxidase.
Helbock
H J
HJ
Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
Thompson
J
J
Yeo
H
H
Ames
B N
BN
D000818:Animals; D000911:Antibodies, Monoclonal; D015415:Biomarkers / Q000652:urine; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004249:DNA Damage; D004563:Electrochemistry / Q000379:methods; D004926:Escherichia coli; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006147:Guanine / Q000031:analogs & derivatives* / Q000652:urine; D006801:Humans; D007223:Infant; D012343:RNA, Transfer / Q000737:chemistry*; D051381:Rats; D013056:Spectrophotometry, Ultraviolet; D014969:Xanthine Oxidase / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D015415:Biomarkers; C024829:8-hydroxyguanine; D006147:Guanine; D012343:RNA, Transfer; C099523:N(2)-methyl-8-oxoguanine; D014969:Xanthine Oxidase