The structure of rooster-comb dermatan sulfate. Characterization and quantitative determination of copolymeric, isomeric tetra- and hexa-saccharides

Abstract

Rooster-comb dermatan sulfates RC-20 and RC-30 were subjected to depolymerization-desulfation in hot dimethyl sulfoxide containing 10% of water to give almost quantitatively nonsulfated, even-numbered oligosaccharides having 2-acetamido-2-deoxy- d-galactose residues at the reducing terminals. They were fractionated on an anion-exchange resin with a linear gradient of lithium chloride into even-numbered oligosaccharide fractions from di- to dodeca-saccharide. Each fraction of di-, tetra-, and hexa-saccharide was isolated and further fractionated on an anion-exchange resin with a linear gradient of formic acid. All the oligosaccharide isomers that could theoretically exist (two disaccharide, four tetrasaccharide, and eight hexasaccharide fractions) were separated, and the sequences in disaccharide units were determined. The recoveries of the total amount of the di-, tetra-, and hexa-saccharide isomers isolated based on the starting RC-20 and RC-30 were 63.1 and 50.4%, respectively. The N-acetyldermosine-to- N-acetylchondrosine ratio in the disaccharide fractions from RC-20 and RC-30 had a value approximately equal to the IdoA-to-GlcA ratio. The yield of the hybrid oligomer containing N-acetylchondrosine and N-acetyldermosine was lower than expected, suggesting that the polysaccharide-chain structure of the dermatan sulfates (RC-20 and RC-30) of rooster comb contains many saccharide-chain blocks in which N-acetylchondrosine or N-acetyldermosine units are bonded sequentially.