Estimation of Gibbs energy changes of central metabolism reactions

Changes in Gibbs energies of metabolic reactions of glycolysis and Krebs cy cle have been calculated from literature data including Delta G, pK values, and complex formation constants values. Neutral, charged species and Mg-co mplexes are included in the data base. Results show that most of the reacti ons investigated proceed near thermodynamic equilibrium conditions whereas the reactions out of equilibrium are related to the metabolic regulation an d seem associated with cyclic sequences or with parallel pathways. Examples of fructose 6-phosphate/fructose 1,6-diphosphate cycle and phosphotranfera se system and hexokinase are presented.