Formation of 8-methylguanine as a result of DNA alkylation by methyl radicals generated during horseradish peroxidase-catalyzed oxidation of methylhydrazine.
Methylhydrazine oxidation promoted by horseradish peroxidase-H2O2 or ferricyanide led to the generation of high yields of methyl radicals and to the formation of 7-methylguanine and 8-methylguanine upon interaction with calf thymus DNA. Methyl radicals were identified by spin-trapping experiments with alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone and tert-nitrosobutane. The methylated guanine products were identified in the neutral hydrolysates of treated DNA by high pressure liquid chromatography (HPLC) analysis and spiking with authentic samples. The structure of 8-methylguanine, a product not previously reported in enzymatic systems, was confirmed by HPLC chromatography, UV absorbance, and mass spectrometry. The formation of 8-methylguanine suggests a possible role for carbon-centered radicals as DNA-alkylating agents.
Augusto
O
O
Department of Biochemistry, Universidade de São Paulo, Brazil.
Cavalieri
E L
EL
Rogan
E G
EG
RamaKrishna
N V
NV
Kolar
C
C
D000478:Alkylation; D004247:DNA / Q000302:isolation & purification / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006147:Guanine / Q000031:analogs & derivatives* / Q000032:analysis; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006868:Hydrolysis; D013058:Mass Spectrometry; D009002:Monomethylhydrazine / Q000378:metabolism*; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet
D005609:Free Radicals; C066771:8-methylguanine; D006147:Guanine; D004247:DNA; D006735:Horseradish Peroxidase; D009002:Monomethylhydrazine