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Proton‐Coupled Electron Transfer of Unsaturated Fatty Acids and Mechanistic Insight into Lipoxygenase
Author(s) -
Fukuzumi Shunichi
Publication year - 2006
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200690223
Subject(s) - chemistry , radical , electron paramagnetic resonance , electron transfer , lipoxygenase , linoleic acid , proton coupled electron transfer , photochemistry , unsaturated fatty acid , redox , yield (engineering) , fatty acid , regioselectivity , proton , organic chemistry , enzyme , catalysis , nuclear magnetic resonance , physics , materials science , quantum mechanics , metallurgy
A proton‐coupled electron transfer (PCET) process plays an important role in the initial step of lipoxygenases to produce lipid radicals which can be oxygenated by reaction with O 2 to yield the hydroperoxides stereoselectively. The EPR spectroscopic detection of free lipid radicals and the oxygenated radicals (peroxyl radicals) together with the analysis of the EPR spectra has revealed the origin of the stereo‐ and regiochemistry of the reaction between O 2 and linoleyl (= (2 Z )‐10‐carboxy‐1‐[(1 Z )‐hept‐1‐enyl]dec‐2‐enyl) radical in lipoxygenases. The direct determination of the absolute rates of H‐atom‐transfer reactions from a series of unsaturated fatty acids to the cumylperoxyl (= (1‐methyl‐1‐phenylethyl)dioxy) radical by use of time‐resolved EPR at low temperatures together with detailed kinetic investigations on both photoinduced and thermal electron‐transfer oxidation of unsaturated fatty acids provides the solid energetic basis for the postulated PCET process in lipoxygenases. A strong interaction between linoleic acid (= (9 Z ,12 Z )‐octadeca‐9,12‐dienoic acid) and the reactive center of the lipoxygenases (Fe III OH) is suggested to be involved to make a PCET process to occur efficiently, when an inner‐sphere electron transfer from linoleic acid to the Fe III state is strongly coupled with the proton transfer to the OH group.