On the Physical and Evolutionary Limits to the Rates of Enzyme-Catalyzed Reactions

An existing model for the rate coefficients of enzyme-catalyzed processes involves the regularized gamma function of Euler replacing the exponential dependence of the rate coefficient from the reaction barrier. The application of this model to experimental data, on one hand, validates the model by correctly describing the negative curvature of Eyring plots. On the other hand, this analysis evidences that enzymes never reach the maximum theoretical efficiency, a counterintuitive fact that requires an explanation. This work interprets this evolutionary limit in terms of the necessity of living systems to achieve and maintain homeostasis. Further validation of the expression for the rate coefficients comes from the analysis of the discrepancy between the theoretically predicted energy difference between reactants and products in a chemical equilibrium and the corresponding value obtained by regression to the classical expression for the equilibrium constant. The discrepancy is resolved by making use of the proposed model.