Thermodynamic Limitations and Metabolite Effects on Enzyme Activities. Metabolite names are in lowercase and reaction names are in uppercase. (A) Histograms of ΔG* in kJ for each reaction across different conditions. Bin height indicates the number of conditions with ΔG* between the two values on the x-axis. Values less than −10 kJ indicate a strong thermodynamic driving force for the reaction, and values near 0 indicate proximity to equilibrium. Mean values and standard deviations for ΔG* for each reaction are also shown at the bottom right. No histograms are shown for irreversible reactions. Abbreviations are as follows. PGI: phosphoglucose isomerase, GAPD: glyceraldehyde phosphate dehydrogenase, ALDO: fructose bisphosphate aldolase, TPI: triosephosphate isomerase, PGK: phosphoglycerate kinase, PGM: phosphoglucomutase, ENO: enolase, RPE: ribulose 5-phosphate epimerase, RPI: ribulose 5-phosphate isomerase, TKT1: transketolase I, TKT2: transketolase 2, TALA: transaldolase (B) Apparent secondary effects of metabolite levels in the central metabolism. Inhibition effects are denoted by lines with perpendicular ends. Activation effects are denoted by lines with arrow tips. Intermediate effects (concentration same order of magnitude as binding coefficient) are in yellow. Stronger effects are in red (inhibition) or green (activation).