A Refined Analysis of Superoxide Production by Mitochondrial sn-Glycerol 3-Phosphate Dehydrogenase
A Refined Analysis of Superoxide Production by Mitochondrial sn-Glycerol 3-Phosphate Dehydrogenase
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DOI：
10.1074/jbc.m112.397828
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发表时间：
2012-12-14
影响因子：
4.8
通讯作者：
Brand, Martin D.
中科院分区：
文献类型：
--
作者：
Orr, Adam L.;Quinlan, Casey L.;Brand, Martin D.
通过线粒体sn-甘油3-磷酸脱氢酶（mGPDH）氧化sn-甘油3-磷酸是将胞质还原当量转移到线粒体电子传递链的主要途径。已知以一定范围的速率并从链内的多个位点产生H2 O2。速率和部位取决于组织来源、3-磷酸甘油和钙的浓度以及不同电子传递链抑制剂的存在。我们报告了一个详细的检查过氧化氢生产过程中的甘油3-磷酸氧化骨骼肌，棕色脂肪，大脑和心脏线粒体的条件下，强调mGPDH本身是超氧化物和过氧化氢的来源。重要的是，我们表明，H2 O2生产的相当大一部分通常归因于mGPDH起源，而不是从电子流通过泛醌池到复杂的II。当复合物II被抑制和mGPDH是唯一的超氧化物生产者，超氧化物的产生速率取决于甘油3-磷酸和钙的浓度，并与预测的泛醌池的还原状态呈正相关。mGPDH-特异性超氧化物生产平台的速率与线粒体中超氧化物生产的其他主要位点相当，超氧化物生产中心没有表现出过度还原的迹象，最大超氧化物生产速率与mGPDH活性相关，在四种不同的组织中。mGPDH产生的超氧化物大致相等地朝向线粒体内膜的每一侧，这表明mGPDH的Q-结合口袋是超氧化物产生的主要位点。这些结果阐明了mGPDH产生超氧化物的最大速率和机制。
The oxidation of sn-glycerol 3-phosphate by mitochondrial sn-glycerol 3-phosphate dehydrogenase (mGPDH) is a major pathway for transfer of cytosolic reducing equivalents to the mitochondrial electron transport chain. It is known to generate H2O2 at a range of rates and from multiple sites within the chain. The rates and sites depend upon tissue source, concentrations of glycerol 3-phosphate and calcium, and the presence of different electron transport chain inhibitors. We report a detailed examination of H2O2 production during glycerol 3-phosphate oxidation by skeletal muscle, brown fat, brain, and heart mitochondria with an emphasis on conditions under which mGPDH itself is the source of superoxide and H2O2. Importantly, we demonstrate that a substantial portion of H2O2 production commonly attributed to mGPDH originates instead from electron flow through the ubiquinone pool into complex II. When complex II is inhibited and mGPDH is the sole superoxide producer, the rate of superoxide production depends on the concentrations of glycerol 3-phosphate and calcium and correlates positively with the predicted reduction state of the ubiquinone pool. mGPDH-specific superoxide production plateaus at a rate comparable with the other major sites of superoxide production in mitochondria, the superoxide-producing center shows no sign of being overreducible, and the maximum superoxide production rate correlates with mGPDH activity in four different tissues. mGPDH produces superoxide approximately equally toward each side of the mitochondrial inner membrane, suggesting that the Q-binding pocket of mGPDH is the major site of superoxide generation. These results clarify the maximum rate and mechanism of superoxide production by mGPDH.