Metabolic Pathways and Regulation · USMLE Step 1

Which enzyme in gluconeogenesis is directly inhibited by fructose-2,6-bisphosphate, thereby preventing gluconeogenesis when glycolysis is active?

  1. Pyruvate carboxylase
  2. Fructose-1,6-bisphosphatase (FBPase-1)
  3. Glucose-6-phosphatase
  4. Phosphoenolpyruvate carboxykinase (PEPCK)
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Correct answer: Fructose-1,6-bisphosphatase (FBPase-1)

Fructose-2,6-bisphosphate inhibits FBPase-1, the enzyme that converts fructose-1,6-bisphosphate to fructose-6-phosphate, thereby downregulating gluconeogenesis when glycolysis is promoted.

Difficulty: Medium Question 14 of 19

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