Bradhyrhizobium japonicum hydrogen-ubiquinone oxidoreductase activity: quinone specificity, inhibition by quinone analogs, and evidence for separate sites of electron acceptor reactivity.
Bradhyrhizobium japonicum hydrogen-ubiquinone oxidoreductase activity: quinone specificity, inhibition by quinone analogs, and evidence for separate sites of electron acceptor reactivity.
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日本慢生根瘤菌氢泛醌氧化还原酶活性：醌特异性、醌类似物的抑制以及电子受体反应性不同位点的证据。
DOI：
10.1016/0005-2728(95)00012-8
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
R. Maier
中科院分区：
文献类型：
--
作者：
D. Ferber;B. Moy;R. Maier
纯化的慢生根瘤菌吸氢氢酶不含细胞色素b，具有高效的H2-泛醌氧化还原酶活性。氢氧化膜也催化了H_2-泛醌氧化还原酶的活性，根据H_2-泛醌-1氧化还原酶和H_2-泛醌-1氧化还原酶活性的比较抗霉素A和HQNO滴定，确定了H_2-泛醌氧化还原酶复合体的还原位置。多种醌类化合物都可以作为纯氢酶或膜结合氢酶的电子受体，包括泛醌-0(Q0)、泛醌-1(Q1)、杜罗醌和甲苯二酮，显示了相对较松散的对苯二酚头部基团的底物特异性。氧化还原电位和苯二酚结构共同决定了氢酶的转化效率。在短链泛醌中，类异戊二烯链长对Km有很大影响，每增加一个类异戊二烯单元，膜结合酶的Km值降低一个数量级以上。对于纯酶，Q0、Q1和Q2的Km值分别为1.97 mm、68.8μM和3.1μM。对于纯酶来说，底物类异戊二烯链长对Vmax也有影响。苯醌类似物(2-正庚基-4-羟基喹啉N-氧化物和抗霉素A)对H2依赖的Q1和MB还原的抑制模式明显不同，两种活性的最适pH也有明显差异。另外，化学修饰剂重氮苯磺酸盐对两种氢相关的电子受体活性(Q1和MB)表现出不同的时间依赖失活模式。因此，泛醌和MB在原位氢酶复合体中通过不同的机制(可能在不同的位置)反应。在bc1复合体上，抗霉素A和抗霉素A对氢泛醌氧化还原酶活性的抑制模式明显不同。据我们所知，这是首次报道抗菌素A对氢酶复合体的抑制作用，也是对初级脱氢酶的苯醌还原部位的抑制作用。当纯氢酶在没有连二亚硫酸盐的情况下被测定时，在达到完全活性之前观察到一个延迟(滞后阶段)。这种滞后期的长度(以分钟为单位)与泛醌浓度成反比，当泛醌水平饱和时，延迟期大大缩短(但没有消除)。Q1和MB均为电子受体，且Q1的滞后期显著长于MB。因此，在周转期间氢酶的还原激活需要与氢酶结合的电子受体。
The purified H2-uptake hydrogenase of Bradyrhizobium japonicum, containing no cytochrome b, catalyzed efficient H2-ubiquinone oxidoreductase activity. Hydrogen-oxidizing membranes also catalyzed H2-ubiquinone oxidoreductase activity, and the site of ubiquinone reduction was localized to the H2-quinone oxidoreductase complex based on comparative antimycin A and HQNO titrations of both H2-ubiquinone-1 oxidoreductase and ubiquinol-1 oxidase activities. A variety of quinones could function as electron acceptors of both pure or membrane-bound hydrogenase, including ubiquinone-0 Q0), ubiquinone-1 (Q1), duroquinone and menadione, indicating relatively loose substrate specificity with regard to the quinone head group. Both the redox potential and the quinone structure determined the efficiency of hydrogenase turnover. Among short-chain ubiquinones, the isoprenoid chain length had a profound affect on Km, with each additional isoprenoid unit resulting in the Kmof the membrane-bound enzyme to decrease more than an order of magnitude. For pure enzyme, the Kmvalues for Q0, Q1and Q2were 1.97 mM, 68.8 μM and 3.1 μM, respectively. Vmaxwas also influenced by the substrate isoprenoid chain length for the pure enzyme. The inhibition patterns of H2-dependent Q1versus MB reduction by the quinone analogs (2-n-heptyl-4-hydroxyquinoline N-oxide and Antimycin A) were significantly different, and clear differences in pH optima for the two activities were observed. In addition, the two hydrogen-dependent electron acceptor activities (Q1and MB) exhibited different time-dependent inactivation patterns by the chemical modification reagent diazobenzene sulfonate. Ubiquinone and MB therefore react by different mechanisms (perhaps at different sites) within the hydrogenase complex in situ. The inhibition pattern of hydrogen-ubiquinone oxidoreductase activity by antimycin A was clearly different than antimycin A inhibition of ubiquinol oxidation at the bc1complex. This is, to our knowledge, the first report of antimycin A inhibition of a hydrogenase complex, and also of a quinone reducing site of a primary dehydrogenase. When pure hydrogenase is assayed in the absence of dithionite, a delay (lag phase) is observed prior to attainment of full activity. The length of this lag period (in minutes) was inversely dependent on ubiquinone concentration, and was greatly reduced (but not eliminated) at saturating ubiquinone levels. These effects were obtained with both Q1and MB as electron acceptor, and the lag phases with Q1were significantly longer than with MB. Electron acceptor binding to hydrogenase is thus required for reductive activation of hydrogenase during turnover.
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日本慢生根瘤菌膜结合氢化酶的氢泛醌氧化还原酶活性。
影响因子：
2.1
作者：
Ferber,DM;Maier,RJ
通讯作者：
Maier,RJ
电子顺磁共振研究巨大脱硫弧菌含镍氢化酶的活化机制和催化循环。
DOI：
--
发表时间：
1985
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Teixeira,M;Moura,I;Xavier,AV;Huynh,BH;DerVartanian,DV;PeckJr,HD;LeGall,J;Moura,JJ
通讯作者：
Moura,JJ
影响因子：
11.3
作者：
A. Przybyla;Jeffery Robbins;N. Menon;H. D. Peck
通讯作者：
A. Przybyla;Jeffery Robbins;N. Menon;H. D. Peck
影响因子：
2.9
作者：
Ferber,DM;Maier,RJ
通讯作者：
Maier,RJ