PATTERNS OF URONOSYL EPIMERIZATION AND 4- 6-O-SULFATION IN CHONDROITIN/DERMATAN SULFATE FROM DECORIN AND BIGLYCAN OF VARIOUS BOVINE-TISSUES/

Dermatan sulphate is a co-polymer of two types of disaccharide repeats : D-glucuronate-N-acetylgalactosamine and L-iduronate-N-acetylgalactos amine. The former can be O-sulphated at C-4 or C-6 of the galactosamin e, whereas the latter contains almost exclusively 4-O-sulphated galact osamine. A minor proportion of the L-iduronate may be O-sulphated at C -2. Chondroitin sulphate has no L-iduronate- containing repeats. We ha ve used our recently developed methods for sequence analysis of galact osaminoglycans to investigate the structure of dermatan/chondroitin su lphates of the proteoglycans decorin and biglycan derived from various bovine tissues, like dermis, sclera, tendon, aorta, cartilage and bon e. The glycan chains, radioiodinated at the reducing end, were partial ly cleaved with specific enzymes (chondroitin lyases), and subjected t o high-resolution polyacrylamide gel electrophoresis, blotting and aut oradiography to identify fragments extending from the labelled reducin g end to the point of cleavage. We used chondroitin B lyase to identif y the location of L-iduronate, chondroitin AC-I lyase to locate D-gluc uronate and chondroitin C lyase to cleave where D-glucuronate residues were succeeded by 6-O-sulphated N-acetylgalactosamine. We could demon strate tissue-specific, periodic and wave-like patterns of distributio n for the two epimeric uronic acids, as well as specific patterns of s ulphation in dermatan sulphates derived from either decorin or biglyca n. For example, some dermatan sulphates contained n-glucuronate-rich d omains that were always 6-sulphated (scleral decorin), others were alw ays 4-sulphated (decorin from bovine dermis, cartilage and bone; bigly can from aorta) or 6-sulphated near the linkage region, but 4-sulphate d in more distal domains (decorin from porcine dermis and bovine tendo n). Decorin from bone and articular cartilage, as well as biglycan fro m articular and nasal cartilage, carried largely chondroitin sulphate chains, but also some dermatan sulphate, whereas galactosaminoglycan c hains derived from aggrecan of nasal cartilage were free of L-iduronat e. Decorin and biglycan from the same tissue (articular cartilage or s clera) had similar glycan chains. The two side chains in a biglycan mo lecule are probably also similar to one another. The portion of the gl ycan chains nearest to the core protein was substituted with charged g roups to a variable degree, which may correlate with the structural fe atures of the main chain.