Studies on Keratosulfates

The structure of the carbohydrate moiety of old human rib cartilage keratosulfate (KS II) was investigated by methylation of the mucopolysaccharide and its desulfated analogue. The methods used were identical with those used previously for cornea keratosulfate. The methyl ethers were characterized either as crystalline derivatives or by paper, thin layer, or gas-liquid chromatography. The data are interpreted as a repeating unit of N-acetyllactosamine polymerized via 1 → 3-linkages to the galactose. Position 6 of N-acetylglucosamine or d-galactose, or both, is esterified with sulfate. The polysaccharide appears to be more highly branched than that from cornea. Furthermore, d-mannose was isolated from KS II and characterized. Mannose was also found in corneal and other keratosulfates. Catalytic desulfation in methanol yielded two high molecular weight desulfated products, one insoluble in aqueous solvents but soluble in formamide, and the other soluble in water. In addition to sialic acid and l-fucose, some d-galactose was released by methanolysis during the desulfation.