Phosphofructokinase-1 (PFK-1) !

Phosphofructokinase-1 is the main switch of glycolysis: it decides whether glucose is burned according to the cell's energy.

Updated 2026-10-31

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Key facts

Fructose 6-phosphate + ATP → fructose 1,6-bisphosphate + ADP: the committed, rate-limiting step.
A tetrameric allosteric enzyme: ATP is both substrate and inhibitor (it binds a second site).
Muscle uses the PFKM isoform; liver PFKL; red cells mix both.

Activators: AMP, ADP and fructose 2,6-bisphosphate (made by PFK-2, which insulin switches on).
Inhibitors: ATP, citrate and H⁺; glucagon lowers fructose 2,6-bisphosphate in the liver.

PFKM deficiency (Tarui disease, glycogen storage disease VII) causes exercise cramps, myoglobinuria and compensated hemolysis.
In Tarui disease, a carbohydrate-rich meal before exercise makes symptoms worse: it lowers the fatty acids muscle could use.

Think of the answer, then tap the question to see it.

What is the strongest activator of PFK-1?

Fructose 2,6-bisphosphate, which rises with insulin in the liver.

Why does citrate inhibit PFK-1?

It signals that the Krebs cycle has fuel to spare; it slows the entry of glucose.

What disease does muscle PFK deficiency cause?

Glycogen storage disease type VII (Tarui): exercise intolerance, cramps, myoglobinuria and hemolysis.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: PFKM: ATP-dependent 6-phosphofructokinase, muscle type (human) (UniProt, 2026); Glycogen storage disease type VII: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 4PFK: Phosphofructokinase: structure and control (RCSB Protein Data Bank, 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.