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首页> 外文期刊>The Journal of biological chemistry >Evidence for Two Sites of Superoxide Production by Mitochondrial NADH-Ubiquinone Oxidoreductase (Complex I)
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Evidence for Two Sites of Superoxide Production by Mitochondrial NADH-Ubiquinone Oxidoreductase (Complex I)

机译：用线粒体NADH-泛烯酮氧化还原酶进行两种超氧化物产生的证据（综合体I）

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Complex I (NADH-ubiquinone oxidoreductase) can form superoxide during forward electron flow (NADH-oxidizing) or, at sufficiently high protonmotive force, during reverse electron transport from the ubiquinone (Q) pool (NAD+-reducing). We designed an assay system to allow titration of the redox state of the superoxide-generating site during reverse electron transport in rat skeletal muscle mitochondria: a protonmotive force generated by ATP hydrolysis, succinate:malonate to alter electron supply and modulate the redox state of the Q pool, and inhibition of complex III to prevent QH2 oxidation via the Q cycle. Stepwise oxidation of the QH2/Q pool by increasing malonate concentration slowed the rates of both reverse electron transport and rotenone-sensitive superoxide production by complex I. However, the superoxide production rate was not uniquely related to the resultant potential of the NADH/NAD+ redox couple. Thus, there is a superoxide producer during reverse electron transport at complex I that responds to Q pool redox state and is not in equilibrium with the NAD reduction state. In contrast, superoxide production during forward electron transport in the presence of rotenone was uniquely related to NAD redox state. These results support a two-site model of complex I superoxide production; one site in equilibrium with the NAD pool, presumably the flavin of the FMN moiety (site IF) and the other dependent not only on NAD redox state, but also on protonmotive force and the reduction state of the Q pool, presumably a semiquinone in the Q-binding site (site IQ).
机译：在从泛醌（Q）池（NAD + - Rd）的反向电子传输期间，复合物I（NADH-ubiquinone氧化还原酶）可以在正向电子流（NADH氧化）期间形成超氧化物，或者以足够高的原子发电。我们设计了一种测定系统，以允许在大鼠骨骼肌线粒体的逆向电子传输期间滴定超氧化物产生部位的氧化还原状态：由ATP水解产生的原子动物，琥珀酸：丙二酸酯以改变电子供应并调节氧化还原状态Q池，抑制复杂III，防止QH2通过Q循环氧化。通过增加丙二酸酯浓度逐步氧化QH2 / Q池通过复合物的逆向电子传输和旋转酮敏感超氧化物产生的速率减缓了逆向电子的速率。然而，超氧化物生产率与NADH / NAD +氧化还原的所得潜力并不唯一相关夫妻。因此，在复合物I的反向电子传输期间存在超氧化物生产商，其响应Q池氧化还原状态，并且不与NAD减小状态的平衡。相反，在旋转源存在下，转发电子传输期间的超氧化物产生与NAD氧化还原状态无关。这些结果支持两站化的I型超氧化物生产模型;一个位点与NAD池平衡，大概是FMN部分的黄素（位点）和另一个不仅依赖于NAD氧化还原状态，还依赖于NAD氧化还原状态，而且还依赖于Q池的原子动物力和Q池的还原状态，大概是Q Q绑定站点（网站IQ）。

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