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

# Hyaluronic acid (hyaluronan)

Hyaluronic acid is a giant, sulfate-free glycosaminoglycan that holds water: it lubricates joints and gives bulk to the vitreous and skin.

Updated 2026-11-01

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## Key facts

- A repeating disaccharide: glucuronic acid-β1,3-N-acetylglucosamine, joined to the next unit by β1,4.
- The only GAG with no sulfate and no core protein; made at the plasma membrane (hyaluronan synthases) and extruded straight into the matrix.
- It can hold tens of thousands of disaccharides; in cartilage it is the backbone to which many aggrecans bind.
- Hyaluronidases break it down, and in the lysosome β-glucuronidase and β-hexosaminidase finish the job.

**Also called**
Hyaluronan, Hyaluronate

**Formula**
(C₁₄H₂₁NO₁₁)ₙ

**PubChem**
[CID 5288907](https://pubchem.ncbi.nlm.nih.gov/compound/5288907)

## Structure

- The 3D model (PubChem 5288907) is the repeating disaccharide: glucuronate linked β1,3 to N-acetylglucosamine.
- Real chains form highly hydrated coils that fill a huge volume.

## Clinical notes

- In osteoarthritis, synovial hyaluronan gets shorter and less concentrated, and the fluid loses viscosity.
- Some bacteria (streptococci) use hyaluronidase to spread through tissues.
- In the mucopolysaccharidosis caused by hyaluronidase deficiency (MPS IX), it builds up in joints.

## Related conditions

- [Knee Osteoarthritis](https://durgical.com/en/conditions/knee-osteoarthritis/)
- [Hurler syndrome (mucopolysaccharidosis type I)](https://durgical.com/en/conditions/hurler-syndrome/)

## Related

- [Glycosaminoglycans (mucopolysaccharides)](https://durgical.com/en/biochemistry/topics/glycosaminoglycans/)
- [Carbohydrate chemistry](https://durgical.com/en/biochemistry/topics/carbohydrate-chemistry/)
- [UDP-glucose](https://durgical.com/en/biochemistry/molecules/udp-glucose/)
- [Glucose](https://durgical.com/en/biochemistry/molecules/glucose/)

## Test yourself

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

## Which disaccharide makes up hyaluronic acid?

Glucuronic acid linked β1,3 to N-acetylglucosamine, repeated through β1,4 bonds.

## How does hyaluronan differ from the other glycosaminoglycans?

It has no sulfate, no core protein, and is made at the plasma membrane rather than in the Golgi.

## Why do some bacteria make hyaluronidase?

To break down matrix hyaluronan and spread through tissues.

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Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.

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

Sources: [2-(Acetylamino)-2-deoxy-3-O-beta-D-glucopyranuronosyl-beta-D-glucopyranose (CID 5288907)](https://pubchem.ncbi.nlm.nih.gov/compound/5288907) (PubChem, NCBI, 2026) · Public domain; [Hyaluronan metabolism](https://reactome.org/PathwayBrowser/#/R-HSA-2142845) (Reactome, 2026); [Glycosaminoglycan metabolism](https://reactome.org/PathwayBrowser/#/R-HSA-1630316) (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.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/molecules/hyaluronic-acid/