Keratan sulphate

The biological significance of chitosan biomaterials in the hiunan body depends largely on the actions that certain hydrolases exert on them. The resulting chitoohgomers stimulate various cells, while the released monomers are phosphorylated and incorporated into hyaluronan, keratan sulphate and chondroitin sulphate, components of the intracellular matrix and connective tissue [348]. 

Brown GM, Huckerby TN, Abram BL, Nieduszynski lA. Characterization of a non-reducing terminal fragment from bovine articular cartilage keratan sulphates containing a (2-3)-hnked sialic acid and a (l-3)-linked fucose. Biochem. J. 1996 319(1) 137-141. 

HS, heparin sulphate DS, dermatan sulphate KS, keratan sulphate HA, hyaluronic acid PC, phosphatidylcholine PL, phospholipid SL, sphingolipid. 

Keratosulphate Keratan sulphate JV-acetylglucosamine-6-sulphate galactose Bone, cornea, nucleus polposus... 

Ouantock AJ, Fullwood NJ, Thonar EJ, Waltman SR, Capel MS, Ito M, Verity SM, Schanzlin DJ. Macular corneal dystrophy type II multiple studies on a cornea with low levels of sulphated keratan sulphate. Eye 1997 11 57-67. 

Fujita S, lizuka T, Dauber W. Localization of keratan sulphate and chondroi-tin-6-sulphate on the anteriorly, displaced human temporomandibular joint disc-histological and, immunohistochemical analysis. J Oral Rehabil 2001 28 962-970. 

Nieduszynski lA, Huckerby TN, Dickenson JM, Brown GM, Tai GH, Morris HG, Eady S. There are two major types of skeletal keratan sulphates. Biochem J 1990 271 243-245. 

Graham RA, Li TC, Cooke ID, Aplin JD. Keratan sulphate as a secretory product of human endometrium cyclic expression in normal women. Hum Reprod 1994 9 926-9230. 

Olsson L, Stigson M, Perris R, Sorrell JM, Lofberg J. Distribution of keratan sulphate and chondroitin sulphate in wild type and white mutant axolotl embryos during neural crest cell migration. Pigment Cell Res 1996 9 5-17. 

J12. Jenkins, P., Davies, G. R., and Harper, P. S., Morquio-Brailsford disease, A report of four affected sisters with absence of excessive keratan sulphate in the urine. Brit. J. Radiol. 46, 668-675 (1973). 

The common natural ami nopolysaccharides include chitin, chitosan, keratan sulphate, hyaluronic acid, chondroitin and dermatan sulphates, heparin and blood group substances. 

Choi, H. U. and Meyer, K. The structure of keratan sulphates from various sources. Biochem J, 151, 543, 1975. 

A theoretical model for bovine nasal cartilage proteoglycan with uniform side chains of chondroitin sulphate (40 disaccharide residues) and keratan sulphate (15 disaccharide residues) and a random-coil polypeptide backbone has been used to estimate the unperturbed radius and it was found to be about 19 nm for the proteoglycan of molecular weight 1.5 X 10 . ... 

The major high-density proteoglycan isolated from bovine articular cartilage is polydisperse, and contains relatively constant amounts of keratan sulphate. ... 

Keratan sulphates I and II have been isolated and purified from bovine cornea and nasal cartilage, respectively. Desulphation of keratan sulphate I yielded both water-soluble and water-insoluble products, but keratan sulphate II yielded only water-soluble products. The water-soluble form contains glycopeptides from the protein-polysaccharide linkage region, and oligosaccharides derived from the main chain of the glycosaminoglycan associate forming water-insoluble species. 

A comparison of the proteoglycan fractions isolated from non-calcified and calcified portions of bovine nasal cartilage indicates that the relative amount of keratan sulphate increases on calcification with a concomitant decrease in chondroitin sulphate. An elevation of the ratio of chondroitin 4-sulphate to chondroitin 6-sulphate also appears to occur on calcification. 

Components of chick embryos and of new born chickens and rats are capable of synthesis of sulphated glycosaminoglycans. In rats up to two weeks old, only heparan sulphate could be detected, but in chick embryos and newborn chicks keratan sulphate as well as heparan sulphate was detected. 

Compared with normal human articular cartilage, osteoarthritic cartilage shows a significant reduction of dermatan sulphate, chondroitin 6-sulphate, keratan sulphate, and heparan sulphate. The content of glycoprotein also appeared to be reduced. The levels of chondroitin 4-sulphate, keratan sulphate. 

For some polysaccharides, such as keratan sulphate, the linkage sequences seem to have the same sfructixres as the oligosaccharides of conventional glycoproteins and the pathways of their synthesis are presumably the same. Hence mucin-type or complex-type chains can act as link sequences and so dolichol can be involved in some forms of link production. Some other polysaccharides, such as heparin, are attached to sequences that have no known counterpart in typical glycoprotein assembly. 

Glucosamine and galactosamine are very commonly found in sulphated polysaccharides, and, of these, the chondroitin sulphates, dermatan sulphate and keratan sulphate are well known. Heparin and heparan sulphate are more complex polymers and are rather less well understood, but their synthesis has recently attracted a great deal of attention. All of these are considered in detail later in this chapter. 

Sulphate esters of glucosamine are found in keratan sulphate at C-6 and in heparin and heparan sulphate (at C-6- and some C-3-positions). Galactosamine is found as the 4-sulphate in chondroitin-4-sulphate and dermatan sulphate and as the 6-sulphate in chondroitin-6-sulphate it is always present as the A/-acetylamino sugar. Galactosamine substituted at C-3 has been found in a glycolipid of rat kidney(Tadano and Ishizuka, 1982). 

When these chains are attached to a core protein or proteins they form gigantic glycoproteins termed proteoglycans . They tend to have the link sequence Ser-Xyl.Gal.Gal.GlcA-, except that keratan sulphate can be linked by conventional glycoprotein link sequences and no proteoglycan of hyaluronic acid is known. 

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