A new approach to problem of enzymatic catalysis based on excited state of proteins and Le Chatelier’s principle

A hypothesis is proposed that the energy of an exothermic reaction in an aqueous medium can be used to shift the equilibrium in an endothermic reaction involving hydrated ions. This takes place according to Le Chatelier’s principle, and the water dissociation in the homogeneous medium at the protein–water interface gives rise to concentration gradients of ions H+ and OH−. The hypothesis implies that the chemical conversion of the substrate into the product is preceded by an attack of hydrated ions on the protein and their association on the protein (an attack of the nucleophilic agent with the subsequent proton addition). This leads to the formation of a cyclic peroxide in an amino acid residue and to the transition CO → [CO]∗. The return of carbonyl to the ground state ultimately allows to accumulate a part of the free energy and to use it to bring the enzyme to a state where the conformational energy is higher. Thus, an electronically excited state of a protein is regarded as a state required for dark reactions. This means that, along with the substrate sorption on the protein, the other aspect of the behavior of the dynamic system should be taken into account.