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.

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.

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.

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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.

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) (PubChem, NCBI, 2026) · Public domain; Hyaluronan metabolism (Reactome, 2026); Glycosaminoglycan metabolism (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.