Chondroitin 6-sulfate

Chondroitin 6-sulfate is a positional form of chondroitin sulfate characterized by sulfate substitution at the 6-position of N-acetylgalactosamine residues. The numeral identifies a position within a sugar residue; it does not mean that a chain contains exactly six sulfate groups. The alternating chondroitin backbone still contains glucuronic acid and N-acetylgalactosamine-derived residues.

The position can be specified through a defined reaction. Chondroitin 6-sulfotransferase transfers a group from PAPS to the 6-position of eligible N-acetylgalactosamine in chondroitin. Its activity is distinct from that of chondroitin 4-sulfotransferase, which targets a different position.^[ref]

For an original ideal segment, take ten complete two-sugar repeats and suppose every one of its ten eligible amino-sugar residues carries one 6-position substitution. The segment then contains 20 sugar residues and ten sulfate substitutions. Partial modification would change the substitution count without changing the number of backbone residues.

Chondroitin 6-sulfate and chondroitin 4-sulfate can consequently share sugar and sulfate counts while differing in local chemical structure. A total sulfur assay alone cannot identify which positions are modified. Comparing preparations requires stating the structural feature measured, rather than assigning every chain one uniform substitution pattern.^[ref]