Harpers

544 / CHAPTER 48β1,4 β1,3Hyaluronic acid: GlcUA GlcNAcβ1,4GlcUAβ1,3GlcNAc β1,4β1,4 β1,3Chondroitin sulfates: GlcUA GalNAcβ1,4 β1,3GlcUAβ1,3Galβ1,4GalXylβSer4- or 6-SulfateKeratan sulfatesI and II:β1,4 β1,3GlcNAcβ1,4 β1,3Gal GlcNAcGal(GlcNAc, Man)1,6βGlcNAc Asn (keratan sulfate I)6-Sulfate6-SulfateGalNAcαThr (Ser) (keratan sulfate II)Gal-NeuAcHeparin andheparan sulfate:α1,4 α1,4IdUA6-Sulfateα1,4 β1,4GlcN GlcUAα1,4 β1,3GlcNAc GlcUAβ1,3Galβ1,4GalXylβSer2-SulfateSO 3 – or AcDermatan sulfate:β1,4 α1,3IdUAβ1,4 β1,3GalNAc GlcUAβ1,4 β1,3GalNAc GlcUAβ1,3Galβ1,4GalXylβSer2-Sulfate4-SulfateFigure 48–8. Summary of structures of glycosaminoglycans and their attachments to core proteins. (GlcUA,D-glucuronic acid; IdUA, L-iduronic acid; GlcN, D-glucosamine; GalN, D-galactosamine; Ac, acetyl; Gal, D-galactose;Xyl, D-xylose; Ser, L-serine; Thr, L-threonine; Asn, L-asparagine; Man, D-mannose; NeuAc, N-acetylneuraminicacid.) The summary structures are qualitative representations only and do not reflect, for example, theuronic acid composition of hybrid glycosaminoglycans such as heparin and dermatan sulfate, which containboth L-iduronic and D-glucuronic acid. Neither should it be assumed that the indicated substituents are alwayspresent, eg, whereas most iduronic acid residues in heparin carry a 2′-sulfate group, a much smaller proportionof these residues are sulfated in dermatan sulfate. The presence of link trisaccharides (Gal-Gal-Xyl) in the chondroitinsulfates, heparin, and heparan and dermatan sulfates is shown. (Slightly modified and reproduced, withpermission, from Lennarz WJ: The Biochemistry of Glycoproteins and Proteoglycans. Plenum Press, 1980.)Table 48–6. Major properties of the glycosaminoglycans.GAG Sugars Sulfate 1 Linkage of Protein LocationHA GIcNAc, GlcUA Nil No firm evidence Synovial fluid, vitreous humor, loose connective tissueCS GaINAc, GlcUA GalNAc Xyl-Ser; associated withHA via link proteins Cartilage, bone, corneaKS I GlcNAc, Gal GlcNAc GlcNAc-Asn CorneaKS II GlcNAc, Gal Same as KS I GalNAc-Thr Loose connective tissueHeparin GlcN, IdUA GlcN Ser Mast cellsGlcNIdUAHeparan sulfate GlcN, GlcUA GlcN Xyl-Ser Skin fibroblasts, aortic wallDermatan GalNAc, IdUA, GaINAc Xyl-Ser Wide distributionsulfate (GlcUA) IdUa1 The sulfate is attached to various positions of the sugars indicated (see Figure 48–7).