A thermodynamic chemical reaction network drove autocatalytic prebiotic peptides formation

The chemical reaction networks (CRNs), which led to the transition on early Earth from geochemistry to biochemistry remain unknown. We show that the simplest substances—bicarbonate, sulfite/sulfate, and ammonium—were converted to peptides in one geological setting from Sammox (sulfite/sulfate reduction coupled to anaerobic ammonium oxidation)-driven CRNs under mild hydrothermal conditions. Peptides comprise 15 proteinogenic amino acids, endowed Sammox-driven CRNs with autocatalysis. The peptides exhibit both forward and reverse catalysis, with the opposite catalytic impact in sulfite- and sulfate-fueled Sammox-driven CRNs, respectively, at both a variable temperature range and a fixed temperature, resulting in seesaw-like catalytic properties. The variation of substrates concentration and temperature, can influence the redox property of the system, may disrupt the redox homeostasis of Sammox-driven CRNs, therefore, the catalytic orientation of peptides changed due to the stimulation, to maintain system redox homeostasis. The seesaw-like catalytic characteristics of peptides is critical to achieving the sustainability and evolution of Sammox-driven CRNs by preferentially destroy non-functional peptides and preserve peptides with high substrate specificities and/or novel functions. Moreover, the peptides generated from sulfite-fueled Sammox-driven CRNs could catalyze both sulfite-fueled Sammox, and Anammox (nitrite reduction coupling with anaerobic ammonium oxidation) reactions. We propose that Sammox-driven CRNs were critical in the creation of life and that Sammox and Anammox are primordial energy conservation traits.