Dermatan sulfate, repeating units

Dermatan sulfate, found primarily in mammalian skin, has the repeating unit [ — 4)-a-L-idopyranosyluronic acid-(l — 3)-2-acetamido-2-deoxy-4-0-sulfo-/l-D-galactopyranosyl-(l —> ]. Some of the L-iduronic acid residues are sulfated at 0-2.108... 

Dermatan sulfate chains contain repeating units composed of glucuronic acid and N-acetylgalactosamine (Figure 2) as well as iduronic acid and N-acetylgalactosamine. Thus, the dermatan sulfate chain is a co-... 

Most of the polysaccharides of interest in this text are termed glycosaminoglycans, polymers that contain an amino sugar in the repeat unit. Glycosaminoglycans that are abundant in mammalian tissues include hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin-heparan sulfate (see Table 2.4). Most of these glycosaminoglycans,... 

Figure 9.13 Structures of repeating units of glycosaminoglycans (A) hyaluronic acid (B) chondroitin sulfate (C) dermatan sulfate (D) two types of keratan sulfate type I is N linked and type II is O linked (E) heparan sulfate. Sulfate residues have been omitted in all cases.

GAGs are classified into several major types based on the nature of the repeating disaccharide unit heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronan. A hypersulfated form of heparan sulfate called heparin, produced mostly by mast cells, plays a key role In allergic reactions. It is also used medically as an anticlotting drug because of its ability to activate a natural clotting inhibitor called antlthrombln III. 

At least seven types of glycosaminoglycans exist, which differ in the monosaccharides present in their repeating disaccharide units—chondroitin sulfate, dermatan sulfate, heparin, heparin sulfate, hyaluronic acid, and keratan sulfates I and II. Except for hyaluronic acid, the glycosaminoglycans are linked to proteins, usually attached covalently to serine or threonine residues (Fig. 49.9). Keratan sulfate I is attached to asparagine. 

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