Classical kinetic model of central metabolism

Figure 1. Scheme of a kinetic model of central intracellular metabolism. Red arrows indicate glycolysis, magenta pentose-phosphate pathway, green gluconeogenesis, and blue tricaboxylic acid (TCA) cycle. Black arrows indicate exchanges with metabolites, external with respect to the model variables: glc (glucose), g6p (glucose 6-phosphate), f6p (fructose 6phosphate), fbp (fructose phosphate), g3p (glyceraldehyde 3-phosphate), dhap (dihydroxyacetone phosphate), pep (phosphoenol pyruvate), pyr (pyruvate), lac (lactate intracellular), laco (lactate extracellular), accoa (acetyl coenzyme A), oaa (oxaloacetate), cit (citrate), mal (malate), oaa (oxaloacetate), e4p (eritrose 4-phosphate), s7p (sedoheptulose 7phosphate), r5p (ribose 5-phosphate), xu5p (xylulose 5-phosphate), and glu (glutamate). These variables are substrates and products of HK (hexokinase), GP (glucose 6phosphatase), GPH (glycogen phosphorylase), GPI (glucose phosphate isomerase), PFK (phosphofructokinase), FBP (fructose bisphosphatase), Ald (aldolase), TPI (triose phosphate isomerase), pepCK (pep carboxykinase), PK (pyruvate kinase), LDH (lactate dehydrogenase), PDH (pyruvate dehydrogenase complex), CS (citrate synthase), TA (transaldolase), TK (transketolase), and enolase. The reactions between g3p and pep, cit and mal, mal and oaa are lumped and described in the model as one reaction step. g3p and dhap, g6p and f6p, pyr and lac, r5p and xu5p are assumed to be in fast equilibrium and constitute united pool.