[M-IS06] アストロバイオロジー

[MIS06-02] Punctuated transitions in the emergence of biochemistry from geochemistry.

*Shawn E McGlynn^1,2、Liam M Longo^1,2、Harrison B Smith¹、Joshua E Goldford³ (1.Earth-Life Science Institute, Tokyo Institute of Technology、2.Blue Marble Space Institute of Science、3.Physics of Living Systems, Massachusetts Institute of Technology)

キーワード：Origin of life, Earth-Life Science, Metabolism, Network Expansion, Protein fold evolution, Punctuated equilibrium

A major unresolved question in the origin of life is how prebiotic compounds were able to transition to the diversity of biochemical compounds observed in the modern biosphere. Here we construct a model of ancient metabolism using assumptions of primitive coenzyme couplings to construct a feasible path from simple Archean molecular precursors (e.g. phosphate, sulfide, ammonia, simple carboxylic acids and metals) to >4000 biomolecules, spanning the majority of metabolic biochemistry. Our model predicts distinct phases of metabolic evolution, characterized by the emergence of key groups of monomers (carboxylic acids, amino acids, sugars), purines/nucleotide cofactors (NAD, ATP), flavins, and quinones, respectively. The early phases of the expansion are characterized by increased metal-dependence and carboxylation reactions, consistent with an iron and CO₂ rich environment. The production of quinones in the last phase makes oxygenic photosynthesis feasible, enabling the production of O₂ and leading to a >20% increase in biomolecules. Analysis of reaction associated protein folds which facilitate metabolic expansion suggests that nucleotide binding folds increase after the emergence of ATP. Preceding this phase, we found that ancient variants of extant ATP-coupled enzymes involved in de novo purine biosynthesis would have required primitive phosphoryl group transfer ability; our model suggests that promiscuity of ancient ATP-coupled reactions would have been necessary to enable expansion from geochemistry to modern biochemistry.