Classification of Glycosaminoglycans

The six major types of GAG are divided according to monomeric composition, type of glycosidic linkages, and degree and location of sulfate units. The structure of the GAG and their distribution in the body is illustrated in Figure 1. All GAG, except for hyaluronic acid, are sulfated and are found covalently attached to protein, forming proteoglycan monomers.

Figure 1:  Structure of repeating units in and distribution of glycosaminoglycans (GAG). Sulfate groups () are shown in all possible positions. GlcUA and IdUA = glucuronic and iduronic acids; GalNAc = Nacetylgalactosamine; GlcNAc = N-acetylglucosamine; GlcN = glucosamine; Gal = galactose.