Evidence that a reducible xylosyl-lysine is the protein linkage of dermatan sulfate.

Dermatan sulfate, purified by standard methods, displayed one spot at the position of the standard after two-dimensional cellulose acetate electrophoresis and was 99% in GalN, 21.5% in sulfate, and 0.6% in protein; Gal and Xyl (2:1) were the only neutral sugars detected. Its glucuronic acid/iduronic acid ratio was 0.15 and its Mr was approximately equal to 16,000. On reaction with 0.4 M NaOH, its reducing group(s) determined as Glc increased by 71% with concomitant separation of protein and polysaccharide and no alteration of the amino acids; when this reaction was repeated in the presence of 0.3 M NaBH4, only 31% of Lys was detected by standard amino acid analysis and none by TLC of the dansylated amino acids; alkaline cleavage in these conditions yielded only 30% of the original Xyl, xylitol, and a ninhydrin-positive substance different from GalN, which had the retention time of xylitol on Affi-Gel 601 and was also obtained from reduction of dermatan sulfate with a 400-eq excess of Na3BH4 in water under conditions that did not cleave the dermatan sulfate-protein bond. The data indicate that a reducible xylosyl-lysine is the protein linkage of dermatan sulfate from calf ligamentum nuchae.