Detection of free radicals produced from the reaction of cytochrome P-450 with linoleic acid hydroperoxide.
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.
Rota
C
C
Department of Biomedical Sciences, University of Modena, via Campi 276, 41100 Modena, Italy.
Barr
D P
DP
Martin
M V
MV
Guengerich
F P
FP
Tomasi
A
A
Mason
R P
RP
D000818:Animals; D002712:Chlorides; D003198:Computer Simulation; D003497:Cyclic N-Oxides / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D005609:Free Radicals / Q000378:metabolism; D008024:Ligands; D008041:Linoleic Acids / Q000378:metabolism*; D008054:Lipid Peroxides / Q000378:metabolism*; D008956:Models, Chemical; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013113:Spin Labels
D002712:Chlorides; D003497:Cyclic N-Oxides; D005290:Ferric Compounds; D005296:Ferrous Compounds; D005609:Free Radicals; D008024:Ligands; D008041:Linoleic Acids; D008054:Lipid Peroxides; D017382:Reactive Oxygen Species; D013113:Spin Labels; C038649:13-hydroperoxy-9,11-octadecadienoic acid; C020748:ferrous sulfate; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D019388:Cytochrome P-450 CYP1A2; C024555:ferric chloride