Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Strasse 9, 60438 Frankfurt, Germany.
J Biol Chem. 2011 Feb 25;286(8):6080-4. doi: 10.1074/jbc.M110.192823. Epub 2010 Dec 20.
The anaerobic acetogenic bacterium Acetobacterium woodii employs a novel type of Na(+)-motive anaerobic respiration, caffeate respiration. However, this respiration is at the thermodynamic limit of energy conservation, and even worse, in the first step, caffeate is activated by caffeyl-CoA synthetase, which hydrolyzes ATP to AMP and pyrophosphate. Here, we have addressed whether or not the energy stored in the anhydride bond of pyrophosphate is conserved by A. woodii. Inverted membrane vesicles of A. woodii have a membrane-bound pyrophosphatase that catalyzes pyrophosphate hydrolysis at a rate of 70-120 milliunits/mg of protein. Pyrophosphatase activity was dependent on the divalent cation Mg(2+). In addition, activity was strictly dependent on Na(+) with a K(m) of 1.1 mM. Hydrolysis of pyrophosphate was accompanied by (22)Na(+) transport into the lumen of the inverted membrane vesicles. Inhibitor studies revealed that (22)Na(+) transport was primary and electrogenic. Next to the Na(+)-motive ferredoxin:NAD(+) oxidoreductase (Fno or Rnf), the Na(+)-pyrophosphatase is the second primary Na(+)-translocating enzyme in A. woodii.
产乙酸厌氧杆菌采用一种新型的 Na(+)-动力型厌氧呼吸，即咖啡酸呼吸。然而，这种呼吸在能量守恒的热力学极限，更糟糕的是，在第一步中，咖啡酸由咖啡酰辅酶 A 合成酶激活，该酶将 ATP 水解为 AMP 和焦磷酸。在这里，我们研究了产乙酸厌氧杆菌是否能将焦磷酸酐键中的能量储存起来。产乙酸厌氧杆菌的反向膜囊泡具有膜结合的焦磷酸酶，可将焦磷酸水解的速率为 70-120 毫单位/毫克蛋白。焦磷酸酶的活性依赖于二价阳离子 Mg(2+)。此外，活性严格依赖于 Na(+)，K(m)值为 1.1 mM。焦磷酸的水解伴随着 (22)Na(+)向反向膜囊泡腔的转运。抑制剂研究表明，(22)Na(+)转运是原发性和电致的。除了 Na(+)-驱动的铁氧还蛋白：NAD(+)氧化还原酶（Fno 或 Rnf）外，Na(+)-焦磷酸酶是产乙酸厌氧杆菌中的第二种原发性 Na(+)-转运酶。
