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The mechanism of oxidation of model compounds of apo B protein in LDL by Cu(II) complexes

Cu(II)配合物氧化LDL中apo B蛋白模型化合物的机制

基本信息

批准号：
10672101
负责人：
UEDA Jun-ichi
金额：
$ 1.6万
依托单位：
National Institute of Radiological Sciences
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Although it is assumed that the bound copper ion is in redox-active state and capable of producing free radicals initiating the chain reaction, the mechanism of copper-induced peroxidation of LDL is still unclear.Thus, the mechanism of peroxidation of linoleic acid, which is the most abundant polyunsaturated fatty acid in LDL, by some Cu (II) complexes as model compounds of copper bound to apo B protein of LDL was examined by absorption spectroscopy and HPLC. The absorbance at 234 nm due to the formation of conjugated dienes in the reaction of Cu (II) complexes with linoleic acid acid increased with incubation time, reaching a maximum level, and decreased gradually thereafter. The time to reach the maximal value of absorbance at 234 nm was depended on the redox potential of Cu (II) complexes, suggesting that Cu (II) complexes with a high redox potential could oxidize easily linoleic acid to generate linoleic acid hydroperoxide (LOOH). In addition, the addition of hydrogen peroxide (HィイD22ィエD2OィイD22ィエD2) enhanced the oxidation with incubation time more rapidly than in the absence of HィイD22ィエD2OィイD22ィエD2.The addition of ascorbic acid to Cu (II) (HGG) suppressed the increase in absorbance at 234 nm, depending on the increase in the concentration of ascorbic acid. Fe (III) EDTA-mediated oxidation of linoleic acid was accelerated by the addition of ascorbic acid. On the other hand, the addition of Trolox (a water soluble derivative of α-tocopherol) to Cu (II) (HGG) suppressed the increase in absorbance at 234 nm. On contrary, Fe (III) EDTA-mediated oxidation of linoleic acid was completely inhibited by the addition of Trolox.In the presence of acetyl-L-lysine, the reaction of Cu (II) complexes with LOOH led to the formation of fluorescence with excitation maximum at 360 nm and emission maximum at 433 nm.

尽管人们认为结合的铜离子处于氧化还原活性状态，能够产生引发连锁反应的自由基，但铜诱导低密度脂蛋白过氧化的机制仍不清楚。因此，亚油酸是低密度脂蛋白中含量最丰富的多不饱和脂肪酸，以Cu（Ⅱ）配合物为模型化合物，用紫外吸收光谱法和高效液相色谱法研究了Cu（Ⅱ）与LDL载脂蛋白B的结合。在234 nm处的吸光度，由于形成共轭二烯的Cu（II）配合物与亚油酸的反应中的增加与孵育时间，达到最大水平，并逐渐降低之后。在234 nm处达到最大吸光度的时间取决于Cu（II）配合物的氧化还原电位，表明具有高氧化还原电位的Cu（II）配合物容易氧化亚油酸生成亚油酸过氧化氢（LOOH）。此外，加入过氧化氢（H2 O2）后，随着培养时间的延长，H2 O2的氧化作用比不加入H2 O2时更快。加入抗坏血酸后，Cu（II）（HGG）在234 nm处的吸光度增加受到抑制，这取决于抗坏血酸浓度的增加。Fe（III）EDTA介导的亚油酸氧化被加速通过添加抗坏血酸。另一方面，向Cu（II）（HGG）中加入Trolox（α-生育酚的水溶性衍生物）抑制了234 nm处吸光度的增加。在乙酰基赖氨酸存在下，Cu（II）配合物与LOOH反应产生荧光，其最大激发波长为360 nm，最大发射波长为433 nm。