Biochemistry · Enzyme
Fructose-1,6-bisphosphatase (FBPase-1) !
Fructose-1,6-bisphosphatase removes a phosphate from fructose 1,6-bisphosphate and is the main control point of gluconeogenesis.
Updated 2026-11-01
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Key facts
- Fructose 1,6-bisphosphate + H₂O → fructose 6-phosphate + Pi: it bypasses the PFK-1 step.
- It mirrors PFK-1: AMP and fructose-2,6-bisphosphate, which activate PFK-1, inhibit it.
- The 3D structure (1FTA) shows AMP in its allosteric site, away from the active site.
Regulation
- Inhibitors: AMP and fructose-2,6-bisphosphate.
- Glucagon lowers fructose-2,6-bisphosphate and so activates it; insulin does the opposite.
Inhibitors and toxins
- AMP (allosteric)
- Fructose-2,6-bisphosphate
- Synthetic AMP-site inhibitors (studied for type 2 diabetes)
Clinical notes
- FBPase-1 deficiency (autosomal recessive) causes hypoglycaemia with lactic acidosis and ketosis during fasting or fever; fructose makes it worse.
- Running together with PFK-1 would create a futile cycle that only burns ATP; reciprocal regulation prevents it.
Pathways
Related conditions
Related
- Fructose 1,6-bisphosphate
- Phosphofructokinase-1 (PFK-1)
- Phosphoenolpyruvate carboxykinase (PEPCK)
- Glucose-6-phosphatase
Test yourself
Think of the answer, then tap the question to see it.
Which two molecules inhibit fructose-1,6-bisphosphatase?
AMP and fructose-2,6-bisphosphate; both activate PFK-1.
What is a futile cycle and how is it avoided at this step?
PFK-1 and FBPase-1 active together would burn ATP for nothing; fructose-2,6-bisphosphate activates one and inhibits the other.
Why does fructose worsen FBPase-1 deficiency?
Fructose enters as trioses and needs FBPase-1 to become glucose; fructose 1-phosphate also slows glycogenolysis.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: FBP1: Fructose-1,6-bisphosphatase 1 (human) (UniProt, 2026); 1FTA: FRUCTOSE-1,6-BISPHOSPHATASE(D-FRUCTOSE-1,6-BISPHOSPHATE, 1-PHOSPHOHYDROLASE) (E.C.3.1.3.11) COMPLEXED WITH THE ALLOSTERIC INHIBITOR AMP (RCSB Protein Data Bank, 2026); Gluconeogenesis (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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Representative model, for educational purposes only.