Marnett L J, Wilcox A L
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Biochem Soc Symp. 1995;61:65-72. doi: 10.1042/bss0610065.
Reaction of polyunsaturated fatty acid hydroperoxides with metal complexes generates lipid alkoxyl radicals and metal-oxo complexes. Lipid alkoxyl radicals are presumed to be the species responsible for metal-amplified lipid peroxidation because of the chemical analogy of simple organic alkoxyl radicals to the hydroxyl radical. However, polyunsaturated fatty acid alkoxyl radicals exhibit a rich and diverse chemistry that is dominated by intramolecular cyclization to epoxyallylic radicals. Studies described herein demonstrate that the equilibrium between cyclization and ring-opening of epoxyallylic radicals lies overwhelmingly toward cyclization. Thus lipid alkoxyl radicals have a steady-state concentration that is so low that their contribution to metal-amplified lipid peroxidation is insignificant. In fact, the species responsible for metal amplification of lipid peroxidation appears to be the epoxyperoxyl radical formed by coupling the epoxyallylic radical to molecular oxygen.
多不饱和脂肪酸氢过氧化物与金属络合物反应会生成脂质烷氧基自由基和金属氧络合物。由于简单有机烷氧基自由基与羟基自由基在化学性质上的相似性，脂质烷氧基自由基被认为是导致金属催化脂质过氧化的物质。然而，多不饱和脂肪酸烷氧基自由基展现出丰富多样的化学性质，其主要特征是分子内环化生成环氧烯丙基自由基。本文所述的研究表明，环氧烯丙基自由基的环化与开环之间的平衡绝大多数倾向于环化。因此，脂质烷氧基自由基的稳态浓度极低，以至于它们对金属催化脂质过氧化的贡献微不足道。事实上，导致脂质过氧化金属催化放大效应的物质似乎是环氧烯丙基自由基与分子氧偶联形成的环氧过氧自由基。
