School of Marine Science and Technology, Harbin Institute of Technology at Weihai, Weihai, PR China.
State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, PR China.
Nat Ecol Evol. 2023 Nov;7(11):1892-1902. doi: 10.1038/s41559-023-02193-8. Epub 2023 Sep 7.
The reverse tricarboxylic acid cycle (rTCA) is a central anabolic network that uses carbon dioxide (CO) and may have provided complex carbon substrates for life before the advent of RNA or enzymes. However, non-enzymatic promotion of the rTCA cycle, in particular carbon fixation, remains challenging, even with primordial metal catalysis. Here, we report that the fixation of CO by reductive carboxylation of succinate and α-ketoglutarate was achieved in aqueous microdroplets under ambient conditions without the use of catalysts. Under identical conditions, the aqueous microdroplets also facilitated the sequences in the rTCA cycle, including reduction, hydration, dehydration and retro-aldol cleavage and linked with the glyoxylate cycle. These reactions of the rTCA cycle were compatible with the aqueous microdroplets, as demonstrated with two-reaction and four-reaction sequences. A higher selectivity giving higher product yields was also observed. Our results suggest that the microdroplets provide an energetically favourable microenvironment and facilitate a non-enzymatic version of the rTCA cycle in prebiotic carbon anabolism.
反三羧酸循环 (rTCA) 是一个中心代谢网络，利用二氧化碳 (CO)，并且可能在 RNA 或酶出现之前为生命提供了复杂的碳基质。然而，即使有原始金属催化，非酶促促进 rTCA 循环，特别是碳固定，仍然具有挑战性。在这里，我们报告了在环境条件下，在没有催化剂的情况下，在水微滴中通过琥珀酸和 α-酮戊二酸的还原羧化作用固定 CO。在相同条件下，水微滴还促进了 rTCA 循环中的序列，包括还原、水合、脱水和 retro-aldol 裂解，并与乙醛酸循环相连接。这些 rTCA 循环的反应与水微滴相容，如通过两反应和四反应序列所示。还观察到更高的选择性，从而获得更高的产物产率。我们的结果表明，微滴提供了一个能量有利的微环境，并促进了前生物碳同化中 rTCA 循环的非酶促版本。
