Biosynthesis of the Acetylgalactosamine 4,6-Disulfate Unit of Squid Chondroitin Sulfate by Transsulfation from 3′-Phosphoadenosine 5′-Phosphosulfate

A mucopolysaccharide sulfotransferase utilizing 3'-phosphoadenosine 5'-phosphosulfate (sulfate donor) and endogenous proteinpolysaccharides (sulfate acceptor) was characterized from squid cartilage. This enzyme had the unique property of catalyzing the introduction of sulfate into position 6 of an acetylgalactosamine moiety already bearing a sulfate residue at position 4. The sulfotransferase was separated from endogenous proteinpolysaccharides and purified some 9-fold on DEAE-Sephadex A-50. The enzyme thus purified was effective only when exogenous acceptors were added. Although various mono-, di-, and polysaccharides were active as sulfate acceptors, the presence of a sulfate at position 4 of their acetylgalactosamine residue was essential for the acceptor activity. These observations suggest that an interpretation of the known change in type of chondroitin sulfates with phylogenic and ontogenic development must take into consideration the development of a specific family of sulfotransferases with respect to the site of sulfation.