Polydispersity in Sulfation Profile of Oligosaccharide Alditols Isolated from the Protein‐Linkage Region and the Repeating Disaccharide Region of Chondroitin 4‐Sulfate of Bovine Nasal Septal Cartilage

Abstract

Proteoglycans of bovine nasal septal cartilage bear predominantly chondroitin 4-sulfate. After exhaustive chondroitinase ABC digestion of a chondromucoprotein preparation rich in proteoglycans and subsequent reductive beta-elimination, five hexasaccharide alditols were isolated from the glycosaminoglycan-protein linkage region. They were analyzed by enzymatic digestion in conjunction with HPLC and by one-dimensional and two-dimensional 1H-NMR spectroscopy. They share the conventional core saccharide structure delta 4.5HexA alpha 1-3GalNAc beta 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl-ol (where delta 4.5HexA is 4,5-unsaturated hexuronic acid), but have different sulfation profiles. One compound (I) does not contain sulfate. Two of the three monosulfated compounds (II and III) have an O-sulfate group at either C6 or at C4 of the GalNAc residue. The other monosulfated compound (IV) is hitherto unreported and has a O-sulfate at C4 of the Gal residue preceding the GlcA residue, whereas the GalNAc is not sulfated. The disulfated compound (V) has sulfate groups at C4 of both the Gal residue preceding GlcA and the GalNAc residue. The molar ratio of compounds I-V is 38.3:5.9:43.0:1.6:11.2. The structural heterogeneity of these hexasaccharide alditols reflects the polydispersity in the linkage region of the chondroitin sulfate chains. In addition, two trisaccharide and two tetrasaccharide alditols derived from the repeating disaccharide region of the chondroitin sulfate chains were also isolated. Their structures were unambiguously determined by enzymatic analysis and by 1H-NMR spectroscopy as delta 4.5HexA alpha 1-3GalNAc(4-O- or 6-O-sulfate)beta 1-4GlcA-ol and delta 4.5HexA alpha 1-3GalNAc(4-O- or 6-O-sulfate) beta 1-4GlcA beta 1-3GalNAc(4-O-sulfate)-ol, respectively.