Direct ESR detection of pentadienyl radicals and peroxyl radicals in lipid peroxidation: mechanistic insight into regioselective oxygenation in lipoxygenases.
Direct ESR detection of pentadienyl radicals and peroxyl radicals in lipid peroxidation: mechanistic insight into regioselective oxygenation in lipoxygenases.
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DOI：
10.1021/ja044345j
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发表时间：
2005-04
影响因子：
15
通讯作者：
H. Kitaguchi;K. Ohkubo;S. Ogo;S. Fukuzumi
中科院分区：
文献类型：
--
作者：
H. Kitaguchi;K. Ohkubo;S. Ogo;S. Fukuzumi
在不存在O（2）的情况下，在二叔丁基过氧化物（Bu（t）OOBu（t））和多不饱和脂肪酸的光照射下观察到了自由基的良好分辨的ESR谱，使我们能够确定hfc值。亚油基自由基的hfc值表明，自旋密度在C-11位最大。亚油基自由基很容易被O（2）捕获，产生过氧自由基（11-HPO）。通过比较亚油酸和[11，11-（2）H（2）]亚油酸衍生的过氧自由基的ESR谱，表明O（2）主要加在过氧自由基的C-11位上。过氧自由基（13-HPO.），其最初由Bu（t）O.从13-（S）-过氧化氢-9（Z），11（E）-十八碳二烯酸（13-HPOD）中夺取氢形成，发现异构化为11-HPO。通过从13-HPO中除去O（2）。O（2）与亚油基加成生成11-HPO。.这一发现支持了O（2）通过特定的蛋白质通道进入的想法，该通道决定了脂肪氧合酶中O（2）和亚油基自由基之间的双自由基结合的立体化学和区域化学。
Well-resolved ESR spectra of free pentadienyl radicals have been observed under photoirradiation of di-tert-butylperoxide (Bu(t)OOBu(t)) and polyunsaturated fatty acids in the absence of O(2), allowing us to determine the hfc values. The hfc values of linoleyl radical indicate that the spin density is the largest at the C-11 position. The linoleyl radical is readily trapped by O(2) to produce the peroxyl radical (11-HPO.) in which O(2) is added mainly at the C-11 position of the pentadienyl radical as indicated by the comparison of the ESR spectra of peroxyl radicals derived from linoleic acid and [11,11-(2)H(2)]linoleic acid. The peroxyl radical (13-HPO.), which is initially formed by the hydrogen abstraction from 13-(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid (13-HPOD) by Bu(t)O., is found to isomerize to 11-HPO. via removal of O(2) from 13-HPO. and addition of O(2) to linoleyl radical to produce 11-HPO. . This finding supports an idea of O(2) entering via a specific protein channel, which determines the stereo- and regiochemistry of the biradical combination between O(2) and linoleyl radical in lipoxygenases.