Oscillations and control features in glycolysis: numerical analysis of a comprehensive model.

Abstract

We present an analysis of glycolysis based on experimental findings and an interpretation based on concepts of efficiency, resonance response, and control features available in highly nonlinear reaction kinetics. We begin with a model for the glycolytic mechanism that is comprehensive, includes a large number of known activations and inhibitions of enzymes by metabolites, and couples the phosphofructokinase (PFKase) and the pyruvate kinase (PKase) reactions. The PFKase and PKase reactions and the coupling between them are modeled according to experimental information, but we do not attempt to model the glyceraldehyde-3-phosphate dehydrogenase-3-phosphoglycerate kinase reaction. We use experimental data to obtain the best estimates for the kinetic parameters and test the model by calculating the concentration variations of the intermediate metabolites. We confirm oscillatory behavior and calculate the ATP/ADP ratio and the free-energy dissipation for an extended range of the kinetic parameters as a function of the driving force for the glycolytic pathway, a measure of which is the total adenine nucleotide concentration. We find agreement of the calculated results with experimental findings except for the insufficiently represented reactions. Our model shows that the average ATP/ADP ratio is increased and the average free-energy dissipation is decreased in an oscillatory compared with a steady state mode of operation. The average values of the ATP/ADP ratio and of the free energy dissipation change abruptly past the onset of sustained oscillations.