Detection of free radicals produced from the reaction of cytochrome P-450 with linoleic acid hydroperoxide.

Rota C, Barr DP, Martin MV, Guengerich FP, Tomasi A, Mason RP
Biochem J. 1997 328 ( Pt 2): 565-71

PMID: 9371716 · PMCID: PMC1218956 · DOI:10.1042/bj3280565

The ESR spin-trapping technique was employed to investigate the reaction of rabbit cytochrome P-450 1A2 (P450) with linoleic acid hydroperoxide. This system was compared with chemical systems where FeSO4 or FeCl3 was used in place of P450. The spin trap 5, 5'-dimethyl-1-pyrroline N-oxide (DMPO) was employed to detect and identify radical species. The DMPO adducts of hydroxyl, O2-., peroxyl, methyl and acyl radicals were detected in the P450 system. The reaction did not require NADPH-cytochrome P-450 reductase or NADPH. The same DMPO-radical adducts were detected in the FeSO4 system. Only DMPO-.OH radical adduct and carbon-centred radical adducts were detected in the FeCl3 system. Peroxyl radical production was completely O2-dependent. We propose that polyunsaturated fatty acids are initially reduced to form alkoxyl radicals, which then undergo intramolecular rearrangement to form epoxyalkyl radicals. Each epoxyalkyl radical reacts with O2, forming a peroxyl radical. Subsequent unimolecular decomposition of this peroxyl radical eliminates O2-. radical.

MeSH Terms (16)

Animals Chlorides Computer Simulation Cyclic N-Oxides Cytochrome P-450 CYP1A2 Electron Spin Resonance Spectroscopy Ferric Compounds Ferrous Compounds Free Radicals Ligands Linoleic Acids Lipid Peroxides Models, Chemical Rabbits Reactive Oxygen Species Spin Labels

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