PRODUCTION OF SUPEROXIDE RADICALS AND HYDROGEN-PEROXIDE BY NADH-UBIQUINONE REDUCTASE AND UBIQUINOL-CYTOCHROME C REDUCTASE FROM BEEF-HEART MITOCHONDRIA
PRODUCTION OF SUPEROXIDE RADICALS AND HYDROGEN-PEROXIDE BY NADH-UBIQUINONE REDUCTASE AND UBIQUINOL-CYTOCHROME C REDUCTASE FROM BEEF-HEART MITOCHONDRIA
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DOI：
10.1016/0003-9861(77)90035-2
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发表时间：
1977-01-01
影响因子：
3.9
通讯作者：
STOPPANI, AOM
中科院分区：
文献类型：
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作者：
CADENAS, E;BOVERIS, A;STOPPANI, AOM
复合物I （NADH-泛醌还原酶）和复合物III（泛醇-细胞色素c还原酶）添加NADH后产生O2-的最大速率分别为9.8和6.5 nmol/min / mg蛋白质，而在超氧化物歧化酶存在时，相同系统产生H2O2的最大速率分别为5.1和4.2 nmol/min / mg蛋白质。H2O2主要由构成H2O2前体的O2-歧化反应产生。在没有其他特定电子受体的情况下，配合物I生成氧中间体的效率为0.95 mol O2-和0.63 mol H2O2/mol NADH。由于泛醌是复合物I和复合物III唯一共同的主要成分，因此泛醌的还原形式似乎负责将O2还原为O2-，复合物I的H2O2生成被鱼藤酮抑制，而补充外源泛醌的复合物I增加了H2O2的生成速率。添加的醌类产生过氧化物的效率依次为Q1 > Q0 > Q2 > Q6 = Q10，这与醌类作为配合物I的电子受体的能力一致。在添加的体系中，外源醌被配合物I还原，并被O2非酶氧化。醌自氧化过程中产生的O2-和H2O2为泛醌作为过氧化物发生器的作用提供了额外的证据。在含氧缓冲液中，泛醇（Q0H2）、苯并喹啉、杜喹啉和甲萘二醇生成O2-， k3值为0.1 ~ 1.4 M-1。s-1和H2O2的k4值为0.009 ~ 4.3 M-1。s - 1。
Complex I (NADH-ubiquinone reductase) and Complex III (ubiquinol-cytochrome c reductase) supplemented with NADH generated O2- at maximum rates of 9.8 and 6.5 nmol/min per mg of protein, respectively, while, in the presence of superoxide dismutase, the same systems generated H2O2 at maximum rates of 5.1 and 4.2 nmol/min per mg of protein, respectively. H2O2 was essentially produced by disproportionation of O2-, which constitutes the precursor of H2O2. The effectiveness of the generation of oxygen intermediates by Complex I in the absence of other specific electron acceptors was 0.95 mol of O2- and 0.63 mol of H2O2/mol of NADH. A reduced form of ubiquinone appeared to be responsible for the reduction of O2 to O2-, since ubiquinone constituted the sole common major component of Complexes I and III, H2O2 generation by Complex I was inhibited by rotenone, and supplementation of Complex I with exogenous ubiquinones increased the rate of H2O2 generation. The efficiency of added quinones as peroxide generators decreased in the order Q1 > Q0 > Q2 > Q6 = Q10, in agreement with the quinone capacity of acting as electron acceptor for Complex I. In the supplemented systems, the exogenous quinone was reduced by Complex I and oxidized nonenzymatically by O2. Additional evidence for the role of ubiquinone as peroxide generator is provided by the generation of O2- and H2O2 during autoxidation of quinols. In oxygenated buffers, ubiquinol (Q0H2), benzoquinol, duroquinol and menadiol generated O2- with k3 values of 0.1-1.4 M-1 .cntdot. s-1 and H2O2 with k4 values of 0.009-4.3 M-1 .cntdot. s-1.