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.

尽管假设结合的铜离子处于氧化还原活性状态并且能够产生自由基引发链式反应，但铜诱导LDL过氧化的机制仍不清楚。因此，亚油酸的过氧化机制，是LDL中最丰富的多不饱和脂肪酸，通过吸收光谱和HPLC检测了一些Cu(II)络合物作为铜与LDL的apo B蛋白结合的模型化合物。 234 nm处由于Cu(II)络合物与亚油酸的反应中形成共轭二烯而随着孵育时间增加而增加，达到最大水平，并且此后逐渐依赖于在234 nm处达到吸光度最大值的时间。 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)配合物可以容易地氧化亚油酸生成亚油酸氢过氧化物(LOOH)此外，添加过氧化氢(H-D22-D2O-D22-D2)随孵育时间比不存在H-D22-D2O-D22 D2时更快地增强氧化作用。添加抗坏血酸。 Cu (II) (HGG) 抑制 234 nm 处吸光度的增加，具体取决于抗坏血酸浓度的增加添加抗坏血酸可加速 Fe (III) EDTA 介导的亚油酸氧化，而添加 Trolox（α-生育酚的水溶性衍生物）可抑制 Cu (II) (HGG) 的氧化。相反，Fe (III) EDTA 介导的亚油酸氧化被 Trolox 的添加完全抑制。乙酰基-L-赖氨酸的Cu(II)配合物与LOOH反应导致形成荧光，最大激发波长为360 nm，最大发射波长为433 nm。