原细胞
氧化还原
新陈代谢
硫黄
柠檬酸循环
代谢网络
化学
代谢途径
生物化学
有机化学
膜
作者
Joshua E. Goldford,Hyman Hartman,Robert Marsland,Daniel Segrè
标识
DOI:10.1038/s41559-019-1018-8
摘要
It has been suggested that a deep memory of early life is hidden in the architecture of metabolic networks, whose reactions could have been catalyzed by small molecules or minerals before genetically encoded enzymes. A major challenge in unravelling these early steps is assessing the plausibility of a connected, thermodynamically consistent proto-metabolism under different geochemical conditions, which are still surrounded by high uncertainty. Here we combine network-based algorithms with physico-chemical constraints on chemical reaction networks to systematically show how different combinations of parameters (temperature, pH, redox potential and availability of molecular precursors) could have affected the evolution of a proto-metabolism. Our analysis of possible trajectories indicates that a subset of boundary conditions converges to an organo-sulfur-based proto-metabolic network fuelled by a thioester- and redox-driven variant of the reductive tricarboxylic acid cycle that is capable of producing lipids and keto acids. Surprisingly, environmental sources of fixed nitrogen and low-potential electron donors are not necessary for the earliest phases of biochemical evolution. We use one of these networks to build a steady-state dynamical metabolic model of a protocell, and find that different combinations of carbon sources and electron donors can support the continuous production of a minimal ancient ‘biomass’ composed of putative early biopolymers and fatty acids. Understanding the crucial conditions for metabolism in early life is challenging. Using network-based analysis, the authors infer an organo-sulfur proto-metabolic network fuelled by a thioester- and redox-driven variant of the reductive tricarboxylic acid cycle that was capable of producing lipids and keto acids.
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