Structure of the Chondroitin 4-Sulfate-Protein Linkage Region

A disaccharide composed of glucuronic acid and d-galactose has been isolated from chondroitin 4-sulfate and chondroitin 4-sulfate glycopeptides. Its structure has been determined in the following way. (a) Reduction with borohydride demonstrated that galactose constitutes the reducing end of the disaccharide; (b) digestion with β-glucuronidase cleaved the disaccharide into glucuronic acid and galactose, demonstrating a β linkage; (c) periodate oxidation of the disaccharide methylglycoside resulted in no loss of galactose; and (d) oxidation of the disaccharide with lead tetraacetate degraded the galactose moiety to lyxose. This establishes the structure of the disaccharide as 3-O-β-d-glucuronosyl-d-galactose.