Modeling of abiotic ATP synthesis in the context of problems of early biosphere evolution

Abstract

The pathway of adenosine triphosphate (ATP) synthesis in living organisms consists of two autonomous stages; this must be taken into account during the design and analysis of chemical models of the abiogenesis of this key participant of metabolic processes. The first stage is construction of an adenine heterocycle linked to a ribose-5-phosphate molecule to yield AMP, while the following stage is the attachment of phosphoryl residues to the nucleotide molecule by macroergic phosphoanhydride bonds. Involvement of the same set of precursor molecules in both de novo biosynthesis of AMP and abiogenesis of this nucleotide is a very important issue for the analysis of metabolic pathways. Photochemical matrix systems that convert light energy into macroergic bond energy are functional prototypes of photosynthetic phosphorylation; they are of special interest for the construction of abiotic phosphorylation models. Interaction of substrates with a purely mineral matrix (montmorillonite particles) under UV irradiation resulted in the formation of ATP from ADP and orthophosphate. Micro-and nanostructures that formed upon the interaction of the mineral component (sodium polysilicate) with an abiogenic organic pigment (a flavin conjugate with a random amino acid polymer) exhibited phosphorylating activity as well when irradiated with visible light. The properties of AMP and ATP abiosynthesis models investigated are in good accordance with the current views on the environmental conditions of the ancient Earth; evident structural differences exist between these models and the biosynthetic systems in modern organisms.