Sumi Tomonari, Harada Kouji
Research Institute for Interdisciplinary Science, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama, 700-8530, Japan.
Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama, 700-8530, Japan.
Commun Chem. 2021 Oct 22;4(1):149. doi: 10.1038/s42004-021-00585-0.
The origin of life is believed to be chemoautotrophic, deriving all biomass components from carbon dioxide, and all energy from inorganic redox couples in the environment. The reductive tricarboxylic acid cycle (rTCA) and the Wood-Ljungdahl pathway (WL) have been recognized as the most ancient carbon fixation pathways. The rTCA of the chemolithotrophic Thermosulfidibacter takaii, which was recently demonstrated to take place via an unexpected reverse reaction of citrate synthase, was reproduced using a kinetic network model, and a competition between reductive and oxidative fluxes on rTCA due to an acetyl coenzyme A (ACOA) influx upon acetate uptake was revealed. Avoiding ACOA direct influx into rTCA from WL is, therefore, raised as a kinetically necessary condition to maintain a complete rTCA. This hypothesis was confirmed for deep-branching bacteria and archaea, and explains the kinetic factors governing elementary processes in carbon metabolism evolution from the last universal common ancestor.
生命起源被认为是化学自养型的，所有生物量成分都来自二氧化碳，所有能量都来自环境中的无机氧化还原对。还原性三羧酸循环（rTCA）和伍德-Ljungdahl途径（WL）已被公认为最古老的碳固定途径。嗜热硫化杆菌的rTCA，最近被证明是通过柠檬酸合酶意想不到的逆反应发生的，使用动力学网络模型进行了再现，并揭示了由于摄取乙酸时乙酰辅酶A（ACOA）流入，rTCA上还原通量和氧化通量之间的竞争。因此，避免ACOA从WL直接流入rTCA被提出作为维持完整rTCA的动力学必要条件。这一假设在深度分支的细菌和古菌中得到了证实，并解释了控制从最后一个普遍共同祖先开始的碳代谢进化中基本过程的动力学因素。
