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首页> 美国卫生研究院文献>Journal of Bacteriology >Hydrogen Formation and Its Regulation in Ruminococcus albus: Involvement of an Electron-Bifurcating FeFe-Hydrogenase of a Non-Electron-Bifurcating FeFe-Hydrogenase and of a Putative Hydrogen-Sensing FeFe-Hydrogenase
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Hydrogen Formation and Its Regulation in Ruminococcus albus: Involvement of an Electron-Bifurcating FeFe-Hydrogenase of a Non-Electron-Bifurcating FeFe-Hydrogenase and of a Putative Hydrogen-Sensing FeFe-Hydrogenase

机译：球果球菌中的氢形成及其调控：电子分叉的FeFe-加氢酶非电子分叉的FeFe-加氢酶和推定的氢敏感FeFe-加氢酶的参与

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Ruminococcus albus 7 has played a key role in the development of the concept of interspecies hydrogen transfer. The rumen bacterium ferments glucose to 1.3 acetate, 0.7 ethanol, 2 CO2, and 2.6 H2 when growing in batch culture and to 2 acetate, 2 CO2, and 4 H2 when growing in continuous culture in syntrophic association with H2-consuming microorganisms that keep the H2 partial pressure low. The organism uses NAD+ and ferredoxin for glucose oxidation to acetyl coenzyme A (acetyl-CoA) and CO2, NADH for the reduction of acetyl-CoA to ethanol, and NADH and reduced ferredoxin for the reduction of protons to H2. Of all the enzymes involved, only the enzyme catalyzing the formation of H2 from NADH remained unknown. Here, we report that R. albus 7 grown in batch culture on glucose contained, besides a ferredoxin-dependent [FeFe]-hydrogenase (HydA2), a ferredoxin- and NAD-dependent electron-bifurcating [FeFe]-hydrogenase (HydABC) that couples the endergonic formation of H2 from NADH to the exergonic formation of H2 from reduced ferredoxin. Interestingly, hydA2 is adjacent to the hydS gene, which is predicted to encode an [FeFe]-hydrogenase with a C-terminal PAS domain. We showed that hydS and hydA2 are part of a larger transcriptional unit also harboring putative genes for a bifunctional acetaldehyde/ethanol dehydrogenase (Aad), serine/threonine protein kinase, serine/threonine protein phosphatase, and a redox-sensing transcriptional repressor. Since HydA2 and Aad are required only when R. albus grows at high H2 partial pressures, HydS could be a H2-sensing [FeFe]-hydrogenase involved in the regulation of their biosynthesis.
机译：阿鲁米球菌7在种间氢转移概念的发展中发挥了关键作用。瘤胃细菌在分批培养中生长时将葡萄糖发酵为1.3乙酸盐，0.7乙醇，2 CO2和2.6 H2，并在连续培养中与消耗H2的微生物同养相关时发酵为2乙酸盐，2 CO2和4 H2。 H2分压低。该生物利用NAD + 和铁氧还蛋白将葡萄糖氧化为乙酰辅酶A（乙酰辅酶A）和CO2，将NADH还原为乙酰辅酶A转化为乙醇，并使用NADH和还原铁氧还蛋白还原质子。到H2。在所有涉及的酶中，只有催化从NADH形成H2的酶仍然未知。在这里，我们报告说，在葡萄糖上分批培养的白色念珠菌7除铁氧还蛋白依赖性[FeFe]氢化酶（HydA2）外，还含有铁氧还蛋白和NAD依赖性电子分叉[FeFe]氢化酶（HydABC），将来自NADH的H2的endergonic形成与来自还原铁氧还蛋白的H2的exergonic形成耦合。有趣的是，hydA2与hydS基因相邻，该基因被预测为编码具有C端PAS结构域的[FeFe]氢化酶。我们显示hydS和hydA2是较大转录单位的一部分，该转录单位还包含双功能乙醛/乙醇脱氢酶（Aad），丝氨酸/苏氨酸蛋白激酶，丝氨酸/苏氨酸蛋白磷酸酶和氧化还原敏感转录阻遏物的推定基因。由于仅当白bus在高H2分压下生长时才需要HydA2和Aad，因此HydS可能是H2感测[FeFe]氢化酶，参与其生物合成的调控。

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