E. Fructose 2,6-bisphosphate (F26BP) is a small molecule that binds non-covalent

Question

E. Fructose 2,6-bisphosphate (F26BP) is a small molecule that binds non-covalently to metabolic enzymes and modulates their activity. The regulation of phosphofructokinase-1 in glycolysis, a pathway which catabolizes glucose to pyruvate, is shown below in Figure a. Additionally, the regulation of fructose 1,6-bisphosphatase-1 is shown in figure b, and this enzyme catalyzes the reverse reaction in a pathway called gluconeogenesis, which forms glucose from a variety of precursors. 100 100 E 80 +F26BP 80 F26BP 60 > 40 t 40 -F26BP 2 20 20E 4F26BP 0 0 0 0.05 0.1 0.2 0.4 0.7 1.0 2.0 4.0 0 50 100 [Fructose 6-phosphate] (mM) Fructose 1,6-bisphosphate] (??) How does F26BP appear to affect the activity of these enzymes? Do you expect the FBPase-1 reaction to be at equilibrium in physiological conditions given these data? What type of regulation is this?How might the activity of the fictitious enzyme from part D be regulated given these data?

Explanation / Answer

F26BP affects the activity of these enzymes by allosteric regulation i.e. binding at a site distant from the active site (allosteric site) and thereby altering the activity of the enzyme. When it's concentration is high it binds to PFK1 and increases it's affinity towards fructose-6-P and reduces it's affinity towards citrate and ATP. Citrate and ATP are it's inhibitors. Vice versa holds true for FBPase1.

Part D is not provided.

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