Enzyme demands to sustain a total pathway activity of 1 mmol product per second. Contribution of the capacity, the reversibility, and the saturation with substrates or products of each reaction to the demand of enzymes for the CBB cycle, the rCCC, and the 2-HG-rTCA cycle. The figure follows the wording of Noor et al. . “Capacity”: demand of enzyme caused by a limitation by the catalytic rate constant; “Reversibility”: extra amount of enzyme needed because of a backward flux; “Saturation”: additional enzyme necessary because of undersaturation with a substrate or oversaturation with a product. The values present the optimized state as predicted by the ECM algorithm assuming a CO2 concentration of 10 μM and HCO3- concentration of 100 μM. Pyruvate was chosen as a product and formate as a substrate for the pathways. Reaction names correspond to their identifiers in the SBtab model file (Supplementary file Reactions_Composite22_model.tsv (available here)).