FIGURE 2.

Max-min driving force (MDF) optimization (upper panels) and enzyme protein cost estimation (lower panels) of glucose (A) and xylose (B) metabolism pathway of Z. mobilis BC42C Δpdc at the initial state. MDF optimization is presented as the cumulative sum of reaction Gibbs free energies, ΔG′. Blue line with triangle symbols denotes standard Gibbs free energies with all metabolite concentrations fixed at 1 mM, and red line with circle symbols denotes Gibbs free energies when the minimal ΔG′ is optimized with metabolite concentrations constrained ranging from 1 μM to 10 mM except that extracellular glucose/xylose concentration fixed at measured value. Enzyme protein costs were optimized for the minimal protein mass required to support unit pathway flux under the same concentration constraints with MDF optimization. eda, 2-dehydro-3-deoxy-phosphogluconate aldolase; edd, phosphogluconate dehydratase; eno, enolase; g6pdh, glucose-6-phosphate dehydrogenase; gapdh, glyceraldehyde-3-phosphate dehydrogenase; glf, glucose facilitator protein; glk, glucokinase; pgi, glucose-6-phosphate isomerase; pgl, 6-phosphogluconolactonase; pgm, phosphoglycerate mutase; pgk, phosphoglycerate kinase; pyk, pyruvate kinase; rpe, ribulose-5-phosphate epimerase; rpi, ribose-5-phosphate isomerase; tal, transaldolase; tkt, transketolase; xk, xylulokinase; xyl, xylose isomerase.