The allosteric activator fructose-2,6-bisphosphate (F2,6-BP) exerts its principal effect on which pair of enzymes in liver carbohydrate metabolism?

• A Activates glucokinase; inhibits pyruvate kinase
• B Activates phosphoglucomutase; inhibits glycogen phosphorylase
• C Activates glucose-6-phosphate dehydrogenase; inhibits transketolase
• D Activates phosphofructokinase-1; inhibits fructose-1,6-bisphosphatase ✓

Explanation

F2,6-BP is synthesised by phosphofructokinase-2 (bifunctional enzyme) in response to insulin/fed state. It potently activates PFK-1, driving glycolysis, while simultaneously inhibiting fructose-1,6-bisphosphatase, suppressing gluconeogenesis. Glucagon reverses this by activating cAMP-dependent phosphorylation of the bifunctional enzyme, switching it to bisphosphatase mode. This reciprocal control is a key hormonal switch in hepatic glucose metabolism.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.