Glycosaminoglycans disaccharide units

Figure 4-11 The repeating disaccharide units of hyaluronan and other glycosaminoglycans. See Fransson108 and Hardingham and Fosang.107...

Glycosaminoglycans (GAGs) are unbranched chains having repeating disaccharide units, which, with the exception of keratan sulfate, contain an acid and a base. The KS disaccharide unit consists of a hexose and a base. The structures of the different classes of GAG disaccharide units are given in Fig. 1, and summarized in Table I. 

Fig. 1.—Structure of Different Disaccharide Units of Glycosaminoglycans (GAGs).

HA is an unsulfated glycosaminoglycane composed of repeating disaccharide units of D-glucuronic acid and A-acetylglucosaminc linked a-( 1 —4) and p-( 1—3), respectively. HA has special importance because it is a component of the ECM [53] in the soft tissues of mammals, where it mainly ensures water retention [54], This enables the transport of nutrients to, and removal of waste from, cells that do not have a direct blood supply, such a cartilage cells. Moreover, HA is present in the synovial joint fluid, the vitreous humor of the eye, cartilage, blood vessels, and the unbilical cord. More detailed information about the biological functions and physicochemical properties of HA can be found elsewhere [55, 56],... 

Glycosaminoglycans Are Anionic Polysaccharide Chains Made of Repeating Disaccharide Units... 

Six classes of glycosaminoglycans have been described. All are heteropolysaccharides and contain repeating disaccharide units. The compositions and structures of the repeating disaccharide units are shown in Table 11-2 and Figure 11-7. In five glycosaminoglycans, the... 

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