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[Biochemistry](https://durgical.com/en/biochemistry/) · Enzyme

# Hexokinase

Hexokinase opens glycolysis: it puts a phosphate on glucose and traps it inside the cell.

Updated 2026-10-31

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## Key facts

- Glucose + ATP → glucose 6-phosphate + ADP, with Mg²⁺; irreversible.
- Hexokinases I–III: high affinity (low Km, ~0.1 mM), slowed by glucose 6-phosphate; at work in nearly every tissue.
- Glucokinase (liver, β cell): low affinity (Km ~8–10 mM), not slowed by G6P; acts as a glucose sensor.
- When glucose binds, the enzyme closes like a hand (induced fit) and keeps water out.

**Also called**
Glucokinase (hexokinase IV)

**EC number**
[2.7.1.1](https://www.enzyme-database.org/query.php?ec=2.7.1.1)

**Genes**
HK1, GCK

**Structure (PDB)**
[1HKB](https://www.rcsb.org/structure/1HKB)

## Regulation

- Glucose 6-phosphate inhibits hexokinase I–III.
- Insulin induces glucokinase; the GKRP protein keeps it in the nucleus while fasting and releases it when glucose rises.

## Inhibitors and toxins

- 2-deoxyglucose: gets phosphorylated and trapped (FDG-PET)
- Mannoheptulose (glucokinase)

## Clinical notes

- Mutations switching off one copy of glucokinase cause MODY 2: mild, stable hyperglycemia that usually needs no treatment.
- Activating glucokinase mutations cause hyperinsulinemic hypoglycemia.
- Red-cell hexokinase deficiency causes hemolytic anemia and lowers 2,3-BPG.

## Pathways

- [Glycolysis](https://durgical.com/en/biochemistry/pathways/glycolysis/)
- [Glycogen metabolism](https://durgical.com/en/biochemistry/pathways/glycogen-metabolism/)

## Related conditions

- [Type 2 diabetes mellitus](https://durgical.com/en/conditions/type-2-diabetes-mellitus/)

## Related

- [Glucose](https://durgical.com/en/biochemistry/molecules/glucose/)
- [Glucose 6-phosphate](https://durgical.com/en/biochemistry/molecules/glucose-6-phosphate/)
- [ATP (adenosine triphosphate)](https://durgical.com/en/biochemistry/molecules/atp/)

## Test yourself

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

## Why does glucokinase work as a glucose sensor?

Its Km is high (near blood glucose) and its product doesn't inhibit it: its rate follows blood glucose.

## What does losing one copy of GCK cause?

MODY 2: mild, stable hyperglycemia from birth.

## Why does FDG-PET light up tumours?

Hexokinase phosphorylates FDG, which goes no further in glycolysis and is trapped in glucose-hungry cells.

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

Sources: [HK1: Hexokinase-1 (human)](https://www.uniprot.org/uniprotkb/P19367/entry) (UniProt, 2026); [GCK: Hexokinase-4 (human)](https://www.uniprot.org/uniprotkb/P35557/entry) (UniProt, 2026); [GCK gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/gck/) (MedlinePlus, US National Library of Medicine, 2026); [1HKB: Human brain hexokinase type I with glucose and glucose 6-phosphate](https://www.rcsb.org/structure/1HKB) (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/biochemistry/enzymes/hexokinase/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/enzymes/hexokinase/