TITLE: “G-Flux: a metabolic flux and free energy analysis software for interpreting 13C, 2H, 18O, and 15N isotope tracing data.”
ABSTRACT: Metabolic fluxes offer insights into pathway utilization, kinetics, and thermodynamics. Stable isotope tracing and metabolic footprinting are widely used for inferring metabolic fluxes. However, quantitative flux measurement across broad metabolism remains challenging due to our inability to convert multiple isotope distributions into fluxes and integrate exometabolomics data. Here we develop a software application, G-Flux, for computing metabolic fluxes by tracing 13C, 2H, 18O, and 15N. Using the ratio of forward to backward fluxes, G-Flux can compute reaction Gibbs free energies (ΔG). We use G-Flux to compute fluxes and ΔG in E. coli and mammalian cells. Using these results and G-Flux’s ability to simulate isotope labeling, we find that [6-18O1]glucose is ideal for quantifying ΔG of glycolytic reactions and dual tracing of [U-13C6]glucose and [U-15N2]glutamine for quantifying fluxes and ΔG of transaminase and amino acid degradation. Thus, G-Flux facilitates comprehensive metabolic flux and free energy analysis.
