Synthesis and breakdown of universal metabolic precursors promoted by iron

Life builds its molecules from carbon dioxide (CO₂) and breaks them back down again through the intermediacy of just five metabolites, which are the universal hubs of biochemistry¹. However, it is unclear how core biological metabolism began and why it uses the intermediates, reactions and pathways that it does. Here we describe a purely chemical reaction network promoted by ferrous iron, in which aqueous pyruvate and glyoxylate-two products of abiotic CO₂ reduction^2-4-build up 9 of the 11 intermediates of the biological Krebs (or tricarboxylic acid) cycle, including all 5 universal metabolic precursors. The intermediates simultaneously break down to CO₂ in a life-like regime that resembles biological anabolism and catabolism⁵. Adding hydroxylamine^6-8 and metallic iron into the system produces four biological amino acids in a manner that parallels biosynthesis. The observed network overlaps substantially with the Krebs and glyoxylate cycles^9,10, and may represent a prebiotic precursor to these core metabolic pathways.