Alkyl free radicals from the beta-scission of fatty acid alkoxyl radicals as detected by spin trapping in a lipoxygenase system.
2-Methyl-2-nitrosopropane (tNB)-radical adducts from incubation mixtures of fatty acids and soybean lipoxygenase in borate buffer (pH 9.0) were measured by electron paramagnetic resonance (EPR). In addition to the previously reported six-line signal of secondary carbon-centered radicals (RCHR'), a weak signal submerged in the baseline was detected after the peroxidation phase was finished. We propose that this radical is a decomposition product formed via beta-scission of fatty acid alkoxyl radicals. EPR spectra of tNB-radical adducts formed in mixtures of either linoleic acid, arachidonic acid, or 15-hydroperoxyeicosatetraenoic acid with lipoxygenase exhibited hyperfine structure characteristic of tNB/.CH2CH2-R with hyperfine coupling constants: aN = 17.1 G; aH beta = 11.2 G (2H); and aH gamma = 0.6 G (2H). In the case of linolenic acid, this radical tNB/.CH=CH-R' with hyperfine coupling constants: aN = 17.1 G; aH beta = 10.9 G (2H); aH gamma = 1.1 G; and aH delta = 0.5 G. In accord with the decomposition scheme of hydroperoxides derived from unsaturated fatty acids, the radical adducts tNB/.CH2CH2-R and tNB/.CH2-CH=CH-R' were assigned as the pentyl and 2-pentenyl radicals, respectively.
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National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
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D002711:Chloride Peroxidase / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005227:Fatty Acids / Q000737:chemistry*; D005609:Free Radicals; D006454:Hemoglobins / Q000378:metabolism; D008084:Lipoxygenase / Q000378:metabolism*; D015394:Molecular Structure; D013025:Glycine max / Q000201:enzymology; D013113:Spin Labels
D005227:Fatty Acids; D005609:Free Radicals; D006454:Hemoglobins; D013113:Spin Labels; D002711:Chloride Peroxidase; D008084:Lipoxygenase