Pyrophosphate synthesis in iron mineral films and membranes simulating prebiotic submarine hydrothermal precipitates

Abstract

Cells use three main ways of generating energy currency to drive metabolism: (i) conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) by the proton motive force through the rotor-stator ATP synthase; (ii) the synthesis of inorganic phosphate∼phosphate bonds via proton (or sodium) pyrophosphate synthase; or (iii) substrate-level phosphorylation through the direct donation from an active phosphoryl donor. A mechanism to produce a pyrophosphate bond as "energy currency" in prebiotic systems is one of the most important considerations for origin of life research. Baltscheffsky (1996) suggests that inorganic pyrophosphate (P_2O_7^(4-); PP_i) may have preceded ATP/ADP as an energy storage molecule in earliest life, produced by an H^+ pyrophosphatase. Here we test the hypothesis that PP_i could be synthesized in inorganic precipitates simulating hydrothermal chimney structures transected by thermal and/or ionic gradients. Appreciable yields of PP_i were obtained via substrate phosphorylation by acetyl phosphate within the iron sulfide/silicate precipitates at temperatures expected for an alkaline hydrothermal system.

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