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首页> 外文期刊>The FEBS journal >Role of HoxE subunit in Synechocystis PCC6803 hydrogenase
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Role of HoxE subunit in Synechocystis PCC6803 hydrogenase

机译：HoxE亚基在集胞藻PCC6803氢化酶中的作用

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摘要

Cyanobacterial NAD(P)(+)-reducing reversible hydrogenases comprise five subunits. Four of them (HoxF, HoxU, HoxY, and HoxH) are also found in the well-described related enzyme from Ralstonia eutropha. The fifth one (HoxE) is not encoded in the R. eutropha genome, but shares homology with the N-terminal part of R. eutropha HoxF. However, in cyanobacteria, HoxE contains a 2Fe-2S cluster-binding motif that is not found in the related R. eutropha sequence. In order to obtain some insights into the role of HoxE in cyanobacteria, we deleted this subunit in Synechocystis PCC6803. Three types of interaction of the cyanobacterial hydrogenase with pyridine nucleotides were tested: (a) reductive activation of the NiFe site, for which NADPH was found to be more efficient than NADH; (b) H-2 production, for which NADH appeared to be a more efficient electron donor than NADPH; and (c) H-2 oxidation, for which NAD(+) was a much better electron acceptor than NADP(+). Upon hoxE deletion, the Synechocystis hydrogenase active site remained functional with artificial electron donors or acceptors, but the enzyme became unable to catalyze H-2 production or uptake with NADH/NAD(+). However, activation of the electron transfer-independent H/D exchange reaction by NADPH was still observed in the absence of HoxE, whereas activation of this reaction by NADH was lost. These data suggest different mechanisms for diaphorase-mediated electron donation and catalytic site activation in cyanobacterial hydrogenase.
机译：减少蓝藻NAD（P）（+）的可逆氢化酶包含五个亚基。它们中的四个（HoxF，HoxU，HoxY和HoxH）也存在于富营养的Ralstonia eutropha的相关酶中。第五个序列（HoxE）未在富营养芽孢杆菌基因组中编码，但与富营养芽孢杆菌HoxF的N端部分具有同源性。但是，在蓝细菌中，HoxE包含2Fe-2S簇结合基序，而这在相关的富营养罗汉果序列中找不到。为了获得对HoxE在蓝细菌中的作用的一些见解，我们删除了集胞藻PCC6803中的该亚基。测试了蓝细菌氢化酶与吡啶核苷酸的三种类型的相互作用：（a）NiFe位点的还原性活化，发现NADPH的活性高于NADH。 （b）H-2的生产，NADH似乎比NADPH更有效的电子供体; （c）H-2氧化，NAD（+）是比NADP（+）更好的电子受体。 hoxE删除后，集胞藻氢化酶活性位点仍与人工电子供体或受体一起起作用，但该酶变得无法催化H-2的产生或被NADH / NAD（+）吸收。但是，在没有HoxE的情况下，仍观察到NADPH激活了不依赖电子传输的H / D交换反应，而NADH激活了该反应。这些数据表明在蓝细菌氢化酶中黄递酶介导的电子捐赠和催化位点活化的不同机制。

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