부산대학교 도서관

The origin of life is still one of the most exciting scientific quests, one that has deep implications that go far beyond science itself. This thesis explores the possible origins of carbon and energy proto-metabolism in Hadean alkaline hydrothermal vents. I first explore the catalytic properties of Fe(Ni)S minerals in the presence of geologically sustained proton gradients, which lower the kinetic barrier to the reaction between H2 and CO2. This could have promoted nonenzymatic pathways analogous to the acetyl CoA pathway and reverse incomplete Krebs cycle, which drive carbon metabolism in arguably some of the most ancient microorganisms (methanogenic archaea). One of the predicted prebiotic products is thioacetate, which we have shown can be nonenzymatically phosphorolysed to acetyl phosphate (AcP). AcP is widely used in bacteria and archaea as a key intermediary between acetyl CoA and ATP, driving substrate-level phosphorylation of ADP. Its simple structure and high phosphorylating potential suggest it could have acted as a primordial ATP analogue, driving energy metabolism at the beginnings of proto-metabolism. The thesis then explores the phosphorylating capabilities of AcP on ribose, adenosine and ADP, followed by a study on the condensing capabilities of AcP with glycine and AMP. Finally, I explore how carbon and energy metabolism could have interacted during early abiogenesis. The formose reaction nonenzymatically synthesises sugars (carbon metabolism) from formaldehyde, one of the first products of CO2 reduction. AcP could hypothetically direct the formose reaction towards biologically interesting sugars such as ribose using AcP (energy metabolism), rather than the much larger and ramified tars often claimed to be its main products. I show how Hadean alkaline hydrothermal vents could have promoted non-enzymatic pathways analogous to the acetyl CoA pathway and reverse incomplete Krebs cycle. I report that AcP can non-enzymatically phosphorylate a variety of biomolecules, but does not promote the polymerisation of glycine or AMP. Most strikingly, I show that AcP can indeed direct the formose reaction towards the synthesis of pentoses such as ribose.