Classification
Members of the glycosaminoglycan family vary in the type of hexosamine, hexose or hexuronic acid unit they contain (e.g. glucuronic acid, iduronic acid, galactose, galactosamine, glucosamine).
They also vary in the geometry of the glycosidic linkage.
Examples of GAGs include:
| Name | Hexuronic acid / Hexose | Hexosamine | Linkage geometry between predominant monomeric units | Unique features |
| Chondroitin sulfate | GlcUA or GlcUA(2S) | GalNAc or GalNAc(4S) or GalNAc(6S) or GalNAc(4S,6S) | 'GlcUAβ1-3'GalNAcβ1-4 | Most prevalent GAG |
| Dermatan sulfate | GlcUA or IdoUA or IdoUA(2S) | GalNAc or GalNAc(4S) or GalNAc(6S) or GalNAc(4S,6S) | 'IdoUAβ1-3'GalNAcβ1-4 | Distinguished from chondroitin sulfate by the presence of iduronic acid, although some hexuronic acid monosaccharides may be glucuronic acid. |
| Keratan sulfate | Gal or Gal(6S) | GlcNAc or GlcNAc(6S) | -Gal(6S)β1-4GlcNAc(6S)β1-3 | Keratan sulfate type II may be fucosylated. |
| Heparin | GlcUA or IdoUA(2S) | GlcNAc or GlcNS or GlcNAc(6S) or GlcNS(6S) | -IdoUA(2S)α1-4GlcNS(6S)α1-4 | Highest negative charge density of any known biological molecule |
| Heparan sulfate | GlcUA or IdoUA or IdoUA(2S) | GlcNAc or GlcNS or GlcNAc(6S) or GlcNS(6S) | -GlcUAβ1-4GlcNAcα1-4 | Highly similar in structure to heparin, however heparan sulfate's disaccharide units are organised into distinct sulfated and non-sulfated domains. |
| Hyaluronan | GlcUA | GlcNAc | -GlcUAβ1-3GlcNAcβ1-4 | The only GAG that is exclusively non-sulfated |
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