Structure of linkage region between chondroitin polysulfates and peptides

Three different types of chondroitin polysulfate-peptide, chondroitin sulfate D-peptide, chondroitin sulfate E-peptide, and chondroitin sulfate K-peptide, all contained xylose, galactose, and serine in a molar ratio of about 1 : 2 : 1. After treatment with alkali in the presence of NaBH4 and PdCl2, they produced alanine and xylitol in amounts equivalent to the decrease in the amount of serine. Consequently, it was proved that these chondroitin polysulfates are all linked to peptides by O-glycosidic bonds between xylose and serine, as in chondroitin sulfates A and C. It is suggested that the carbohydrate-peptide linkage regions have the same structure in all the chondroitin sulfates, regardless of differences in the structure of the polysaccharide chains, such as the position of sulfate groups and the degree of sulfation.