Identification of radical adducts formed in the reactions of unsaturated fatty acids with soybean lipoxygenase using continuous flow fast atom bombardment with tandem mass spectrometry.
Structures of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) radical adducts formed in the reactions of soybean lipoxygenase with linoleic acid, linolenic acid, and arachidonic acid were determined using continuous flow fast atom bombardment (CF-FAB) combined with tandem mass spectrometry. The radical adducts of these lipoxygenase-dependent reactions were: n-octanoic acid radical, 12,13-dihydroxylinoleic acid radical, 12,13-epoxylinoleic acid radical, and n-pentyl radical from linoleic acid; n-octanoic acid radical, ethyl radical, and cis/trans and/or positional isomers (1- and 3-pentenyl) of pentenyl radical from linolenic acid; and 14,15-epoxyarachidonic acid radical and n-pentyl radical from arachidonic acid. Of these radical adducts, the n-octanoic acid radical from linoleic and linolenic acid, the ethyl radical from linolenic acid, and the 12,13-dihydroxylinoleic acid radical are identified for the first time in the reactions of soybean lipoxygenase. Thus the CF-FAB combined with tandem mass spectrometry employed here, by which both radical adducts and their fragment ions can be detected, is shown to be a powerful tool in the structural identification of free radicals.
Department of Chemistry, Wakayama Medical College, Japan.
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Iwahashi
L J
LJ
Deterding
C E
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Parker
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Mason
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Tomer
D016718:Arachidonic Acid / Q000737:chemistry / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000737:chemistry / Q000378:metabolism*; D015227:Lipid Peroxidation; D008084:Lipoxygenase / Q000378:metabolism*; D009589:Nitrogen Oxides / Q000032:analysis; D010940:Plant Proteins / Q000378:metabolism*; D011725:Pyridines; D013025:Glycine max / Q000201:enzymology*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013113:Spin Labels; D017962:alpha-Linolenic Acid / Q000737:chemistry / Q000378:metabolism*
D005609:Free Radicals; D008041:Linoleic Acids; D009589:Nitrogen Oxides; D010940:Plant Proteins; D011725:Pyridines; D013113:Spin Labels; C043438:alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone; D017962:alpha-Linolenic Acid; D016718:Arachidonic Acid; D019787:Linoleic Acid; D008084:Lipoxygenase