Glinn M A, Lee C P, Ernster L
Department of Biochemistry, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Biochim Biophys Acta. 1997 Jan 16;1318(1-2):246-54. doi: 10.1016/s0005-2728(96)00142-9.
This paper is a study of factors influencing the rate of lipid peroxidation in beef heart submitochondrial particles induced by NAD(P)H via the NADH-ubiquinone oxidoreductase (Complex I) of the respiratory chain. In accordance with earlier observations, both NADH and NADPH initiated lipid peroxidation in the presence of ADP-Fe3+. The rate of the reaction, measured as oxygen consumption and formation of thiobarbituric acid reactive substances, was biphasic as a function of NADH concentration, reaching a maximum at low NADH concentrations and then declining. In contrast, the NADPH-initiated lipid peroxidation showed a monophasic concentration profile of hyperbolic character. Rotenone did not eliminate the biphasicity of the NADH-induced reaction, indicating that this was not due to an antioxidant effect of reduced ubiquinone at high NADH concentrations. This conclusion was further supported by the demonstration that extraction of ubiquinone from the particles did not relieve the inhibition of lipid peroxidation by high NADH concentrations. However rhein, another inhibitor of Complex I, eliminated the biphasicity, and even caused a substantial stimulation of the NADH-induced lipid peroxidation in the particles upon extraction of ubiquinone by pentane. No similar effect occurred in the case of NADPH-induced lipid peroxidation. Furthermore, rhein facilitated both NADH- and NADPH-induced lipid peroxidation even in the absence of added ADP-Fe3+, in a fashion similar to that earlier reported with succinate in the presence of theonyltrifluoroacetone. Based on these findings and measurements of the redox states of ubiquinone and cytochromes in the presence of KCN and NADH or NADPH, it is concluded that Complex I may distinguish between electron input from NADH and NADPH by differences in the site(s) of substrate binding and in the pathways and rates of NADH and NADPH oxidation.
本文研究了通过呼吸链的NADH-泛醌氧化还原酶（复合体I），NAD(P)H诱导牛心亚线粒体颗粒中脂质过氧化速率的影响因素。与早期观察结果一致，在ADP-Fe3+存在的情况下，NADH和NADPH均可引发脂质过氧化。以氧气消耗和硫代巴比妥酸反应性物质的形成来衡量，反应速率随NADH浓度呈双相变化，在低NADH浓度时达到最大值，然后下降。相比之下，NADPH引发的脂质过氧化呈现出双曲线特征的单相浓度分布。鱼藤酮并未消除NADH诱导反应的双相性，表明这并非由于高NADH浓度下还原型泛醌的抗氧化作用。从颗粒中提取泛醌并不能缓解高NADH浓度对脂质过氧化的抑制作用，这进一步支持了这一结论。然而，复合体I的另一种抑制剂大黄酸消除了双相性，甚至在通过戊烷提取泛醌后，能显著刺激颗粒中NADH诱导的脂质过氧化。在NADPH诱导的脂质过氧化中未出现类似效果。此外，即使在没有添加ADP-Fe3+的情况下，大黄酸也能促进NADH和NADPH诱导的脂质过氧化，其方式类似于早期报道的在噻吨基三氟丙酮存在下琥珀酸的情况。基于这些发现以及在KCN和NADH或NADPH存在下对泛醌和细胞色素氧化还原状态的测量，得出结论：复合体I可能通过底物结合位点以及NADH和NADPH氧化途径和速率的差异来区分来自NADH和NADPH的电子输入。
