Fig. 4.

Reaction directions and fluxes. (A) Precision and accuracy of predicting directionalities with different methods. Predicted irreversibilities are given as percentage of the average number of reversible reactions in the different conditions. The percentage of incorrectly predicted irreversibilities is relative to the average number of fluxes that are reversible in the models and have 13C estimates. (B) Example of multimodal predictions of fluxes with TFS for the synthesis of purines and glycine. Orange: serine is converted to glycine, donating one carbon to form 10-formyltetrahydrofolate (10thf), a cofactor for purine synthesis. Blue: glycine is synthesized from threonine and is converted to CO2 and 10thf. Histograms show predicted flux distributions, clustered by the direction of GHMT2r. (C) Distribution of ${\Delta }_{\mathbf{r}}\mathbf{G}\prime °$ (left) and the activity term (right) of GHMT2r, clustered by the direction of the reaction. ${\mathbf{S}}_{\mathbf{i}}^{⊺}$ is the i-th row of ${\mathbf{S}}_{\Gamma }^{⊺}$. (D) Cohen’s d for the distributions of the standard reaction energies and of the activity terms in the two clusters for all reactions in Γ