A primordial and reversible TCA cycle in a facultatively chemolithoautotrophic thermophile

作者：Nunoura Takuro; Chikaraishi Yoshito; Izaki Rikihisa; Suwa Takashi; Sato Takaaki; Harada Takeshi; Mori Koji; Kato Yumiko; Miyazaki Masayuki; Shimamura Shigeru; Yanagawa Katsunori; Shuto Aya; Ohkouchi Naohiko; Fujita Nobuyuki; Takaki Yoshihiro; Atomi Haruyuki; Takai Ken

来源：Science, 2018, 359(6375): 559-562.

DOI：10.1126/science.aao3407

Inorganic carbon fixation is essential to sustain life on Earth, and the reductive tricarboxylic acid (rTCA) cycle is one of the most ancient carbon fixation metabolisms. A combination of genomic, enzymatic, and metabolomic analyses of a deeply branching chemolithotrophic Thermosulfidibacter takaii ABI70S6(T) revealed a previously unknown reversible TCA cycle whose direction was controlled by the available carbon source(s). Under a chemolithoautotrophic condition, a rTCA cycle occurred with the reverse reaction of citrate synthase (CS) and not with the adenosine 5'-triphosphate-dependent citrate cleavage reactions that had been regarded as essential for the conventional rTCA cycle. Phylometabolic evaluation suggests that the TCA cycle with reversible CS may represent an ancestral mode of the rTCA cycle and raises the possibility of a facultatively chemolithomixotrophic origin of life.

• 出版日期2018-2-2