Table I.

Animal GAGs and their major backbone structures

GAG	Major backbone repeat structures
Hyaluronan, hyaluronic acid (HA)	[-4-GlcAβ-1-3-GlcNAc-β1-]n
Chondroitin	[-4-GlcAβ-1-3-GalNAc-β1-]n
CS	[-4-GlcA2Xβ-1-3-GalNAc4X6X-β1-]n
DS	[-4-IdoAα or GlcA2X β–1-3-GalNAc4X6X -β1-]n
Heparosan	[-4-GlcAβ1-4-GlcNAc-α1-]n
HS	[-4-GlcAβ or IdoA2Xα-1-4-GlcNY3X6X-α1-]n
Heparin	[-4-IdoAα or GlcA2Xβ/-1-4-GlcNY3X6X-α1-]n

GlcA, glucuronic acid; IdoA, iduronic acid; GalNAc, N-acetylgalactosamine; GlcNAc, N-acetylglucosamine; GlcN, glucosamine; Y = Ac, SO₃⁻, or H; X = OH or SO₃⁻. With the exception of HA, sulfo groups can be found at various O-positions in the sugar ring. KS, with a non-acidic [-3Galβ1-4GlcNAcβ1]_n backbone, is not listed.