Environmental boundary conditions for the origin of life converge to an organo-sulfur metabolism
Environmental boundary conditions for the origin of life converge to an organo-sulfur metabolism
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DOI：
10.1038/s41559-019-1018-8
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发表时间：
2019-12-01
影响因子：
16.8
通讯作者：
Segre, Daniel
中科院分区：
文献类型：
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作者：
Goldford, Joshua E.;Hartman, Hyman;Segre, Daniel
有人认为，早期生命的深层记忆隐藏在代谢网络的结构中，其反应可能是在基因编码的酶之前由小分子或矿物质催化的。解开这些早期步骤的一个主要挑战是评估在不同的地球化学条件下，仍然被高度不确定性所包围的一个连接的，化学上一致的原代谢的可解释性。在这里，我们结合联合收割机基于网络的算法与化学反应网络的物理化学约束，系统地显示不同的参数组合（温度，pH值，氧化还原电位和可用性的分子前体）可能会影响进化的原代谢。我们对可能轨迹的分析表明，边界条件的子集收敛到基于有机硫的原代谢网络，该网络由能够产生脂质和酮酸的还原性三羧酸循环的硫酯和氧化还原驱动的变体提供燃料。令人惊讶的是，环境来源的固定氮和低电位电子供体是不必要的最早阶段的生化进化。我们使用这些网络之一，建立一个稳态的动态代谢模型的原始细胞，并发现，不同的碳源和电子供体的组合可以支持连续生产的最小的古代“生物质”组成的推定的早期生物聚合物和脂肪酸。
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.