Figure 9

Schematic representation of a simplified model of glycolysis and the trehalose cycle in the yeast Saccharomyces cerevisiae (adapted from[34]). X _i and v _i represent dependent variables and fluxes, respectively. One inhibitory interaction is shown in red. Abbreviations: X₁, extracellular glucose; X₂, intracellular glucose; X₃, glucose 6-phosphate; X₄, trehalose; X₅, fructose 1,6-bisphosphate; X₆, extracellularly accumulating end products (ethanol, glycerol and acetate); X₇, mass diverted into the pentose phosphate pathway; X₈, mass consumed by other pathways (e.g., TCA); v₁, glucose transport; v₂, hexokinase and glucokinase; v₃: aggregated step of all enzymatic steps between glucose 6-phosphate and the production of trehalose; v₄, trehalase; v₅, phosphoglucose isomerase and phosphofructokinase; v₆, aggregated step of all enzymatic steps between fructose 1,6-bisphosphate aldolase and the release of end-products; v₇, flux into the pentose phosphate pathway; v₈, flux towards other pathways (leakage). Metabolites without available experimental measurements are shown in gray. The flux v₆ (blue) is directly measurable from the time series of X₆. Fluxes v₃ and v₄ (green) were estimated using the proposed method.