A theoretical approach to the link between oxidoreductions and pyrite formation in the early stage of evolution

There are two fundamental axioms of surface metabolism theory: (i) pyrite formation from H2S and FeS is proposed as a source of energy for life, and (ii) archaic reductive citric acid cycle is put into the center of a metabolic network. However, the concept fails to indicate how sulfide oxidation ought to be coupled to processes driven by free energy change occurring during pyrite production, and secondly, how reductive citric acid cycle ought to be supplied with row material(s). Recently, the non-enzymatic methylglyoxalase pathway has been recommended as the anaplerotic route for the reductive citric acid cycle. In this paper a mechanism is proposed by which the oxidation of lactate, the essential step of the anaplerotic path, becomes possible and a coupling system between sulfide oxidation and endergonic reaction(s) is also presented. Oxidoreduction for other redox pairs is discussed too. It is concluded that the S(o)/H2S system may have been the clue to energy production at the early stage of evolution, as hydrogen sulfide produced by the metabolic network may have functioned as a coupling molecule between endergonic and exergonic reactions.