The rabbit 15-lipoxygenase preferentially oxygenates LDL cholesterol esters, and this reaction does not require vitamin E
The rabbit 15-lipoxygenase preferentially oxygenates LDL cholesterol esters, and this reaction does not require vitamin E
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DOI：
10.1074/jbc.273.36.23225
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发表时间：
1998-09-04
影响因子：
4.8
通讯作者：
Kühn, H
中科院分区：
文献类型：
--
作者：
Belkner, J;Stender, H;Kühn, H
哺乳动物15-脂氧合酶（15-LOX）氧化低密度脂蛋白（LDL）参与了早期动脉粥样硬化的形成。我们研究了15-LOX/LDL相互作用的分子机制，发现在短期孵育过程中，LDL胆固醇酯优先被15-LOX氧化。即使当低密度脂蛋白颗粒负载游离亚油酸时，亚油酸胆固醇酯也构成了主要的脂氧合酶底物。相比之下，仅检测到少量的游离氧化脂肪酸异构体，并且排除了氧化脂肪酸再酯化成LDL酯脂质部分。当LDL从α-生育酚耗尽时，胆固醇酯的特定氧化没有被阻止，并且产物模式没有改变。在LDL颗粒的低（LDL/LOX比为1：1）和高LOX负载（LDL/LOX比为1：10）下获得类似的结果。在长期孵育（长达24 h）期间，观察到特异性较低的产物模式。然而，当由15-LOX形成的氢过氧脂质立即被磷脂氢过氧化物谷胱甘肽过氧化物酶还原时，当用维生素E耗尽的LDL进行反应时，或当测定样品被稀释时，氧化产物的特定模式在长时间内保留。形成氧化产物的特定模式。在长期孵育过程中，自由基介导的二次反应（导致更非特异性的产物模式）可能变得越来越重要。当形成的过氧氢脂质立即减少时，当使用α-生育酚耗尽的LDL时，或当孵育样品被稀释时，这些次级反应似乎被抑制。可以得出结论，15-LOX引发的LDL氧化构成了一个双类型的加氧酶反应与初始酶和随后的非酶相。这两种类型的反应动脉粥样硬化的生物学相关性将进行讨论。
The oxidation of low density lipoprotein (LDL) by mammalian 15-lipoxygenases (15-LOX) was implicated in early atherogenesis, We investigated the molecular mechanism of 15-LOX/LDL interaction and found that during short term incubations, LDL cholesterol esters are oxygenated preferentially by the enzyme. Even when the LDL particle was loaded with free linoleic acid, cholesteryl linoleate constituted the major LOX substrate. In contrast, only small amounts of free oxygenated fatty acid isomers were detected, and re-esterification of oxidized fatty acids into the LDL ester lipid fraction was ruled out. When LDL was depleted from alpha-tocopherol, specific oxygenation of the cholesterol esters was not prevented, and the product pattern was not altered. Similar results were obtained at low (LDL/LOX ratio of 1:1) and high LOX loading (LDL/LOX ratio of 1:10) of the LDL particle. During long term incubations (up to 24 h), a less specific product pattern was observed. However, when the hydroperoxy lipids formed by the 15-LOX were immediately reduced by the phospholipid hydroperoxide glutathione peroxidase, when the reaction was carried out with vitamin E-depleted LDL, or when the assay sample was diluted, the specific pattern of oxygenation products was retained over a long period of time.These data suggest that mammalian 15-LOX preferentially oxidize LDL cholesterol esters, forming a specific pattern of oxygenation products. During long term incubations, free radical-mediated secondary reactions, which lead to a more unspecific product pattern, may become increasingly important. These secondary reactions appear to be suppressed when the hydroperoxy lipids formed are immediately reduced, when alpha-tocopherol-depleted LDL was used, or when the incubation sample was diluted. It may be concluded that 15-LOX-initiated LDL oxidation constitutes a dual-type oxygenase reaction with an initial enzymatic and a subsequent nonenzymatic phase. The biological relevance of this dual-type reaction for atherogenesis will be discussed.