Müller Volker, Imkamp Frank, Biegel Eva, Schmidt Silke, Dilling Sabrina
Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
Ann N Y Acad Sci. 2008 Mar;1125:137-46. doi: 10.1196/annals.1419.011.
Acetogens use the Wood-Ljungdahl pathway for reduction of carbon dioxide to acetate. This pathway not only allows reoxidation of reducing equivalents during heterotrophic growth but also supports chemolithoautotrophic growth on H(2) + CO(2). The latter argues for this pathway being a source for net energy conservation, but the mechanism involved remains unknown. In addition to CO(2), acetogens can use alternative electron acceptors, such as nitrate or caffeate. Caffeate respiration in the model acetogen Acetobacterium woodii is coupled to energy conservation via a chemiosmotic mechanism, with Na(+) as coupling ion. The pathway and its bioenergetics were solved in some detail very recently. This review focuses on the regulation of caffeate respiration, describes the enyzmes involved, summarizes the evidence for a potential Na(+)-translocating ferredoxin:NAD(+)-oxidoreductase (Rnf complex) as a new coupling site, and hypothesizes on the role of this Rnf complex in the Wood-Ljungdahl pathway.
产乙酸菌利用伍德-Ljungdahl途径将二氧化碳还原为乙酸。该途径不仅能在异养生长过程中使还原当量重新氧化，还支持在H₂ + CO₂上进行化学无机自养生长。后者表明该途径是净能量守恒的一个来源，但其中涉及的机制仍不清楚。除了CO₂，产乙酸菌还能利用其他电子受体，如硝酸盐或咖啡酸盐。模式产乙酸菌伍氏乙酸杆菌中的咖啡酸盐呼吸通过化学渗透机制与能量守恒相偶联，以Na⁺作为偶联离子。该途径及其生物能量学最近已得到较为详细的解析。本综述重点关注咖啡酸盐呼吸的调控，描述所涉及的酶，总结作为新偶联位点的潜在Na⁺转运铁氧化还原蛋白：NAD⁺氧化还原酶（Rnf复合体）的证据，并推测该Rnf复合体在伍德- Ljungdahl途径中的作用。
