Question

How does the regulation of fructose 2,6 bisphosphate concentration differ in plants and animals?

Answer 1

Fructose 2,6-bisposphate is a important metabolite which allosterically affecs the activity of the enzyme phosphofructokinase 1. The enzyme phosphofructokinase1 helps to phosphorylate fructose 6-phosphate and to make of fructose 1,6-bisphosphate, a important byproduct of glycolysis.

Phosphofructokinase 2 is the responsible enzyme for synthesizing the metabolite fructose 2,6-bisphosphate in the cell.

In animals, the primary regulators of fructose 2,6 bisphosphate are the hormone insulin, glucagon and epinephrine which affects the enzyme through phosphorylation/dephosphorylation of it. Glucagon triggers the production of cAMP which activates cAMP dependent protein kinase. This kinase phosphorylates phosphofructokinase 2 (PFK2) enzyme with ATP to inhibit the PFK2 activity, thus reducing the level of fructose 2,6-bisphosphate in the cell.

In plants, when the rate of photosynthesis in the light reaction is high, glyceraldehyde 3-phosphate continuously produced and the production of fructose 2,6-bisphosphate is inhibited thus production of fructose 2,6-bisphosphate is activated. when plants are in dark phase and glyceraldehyde 6-phosphate is not produced.