title: Biosynthesis of dermatan sulfate. I. Formation of L-iduronic acid residues.
abstract: L-[14C]Iduronic acid-containing sulfated galactosaminoglycans were formed by incubation of a fibroblast particulate fraction with UDP-D[14C]glucuronic acid, UDP-N-acetylgalactosamine, and sulfate donor (3'-phosphoadenylylsulfate). The formation of L-iduronic acid was strongly promoted by concomitant sulfation of the polymer. In the absence of sulfate donor 5 to 10% of the [14C]uronic acid residues were L-iduronic acid. However, when 3'-phosphoadenylylsulfate was included in the incubation mixture the amount of L-iduronic acid in the product increased 3 to 5-fold. Furthermore, approximately the same quantity of L-[14C]iduronic acid was recovered from the product formed in a pulse-chase experiment where incorporation of 14C-isotope preceded sulfation. It was therefore concluded that C-5 inversion of D-glucuronic acid to L-iduronic acid occurred on the polymer level as shown previously for the biosynthesis of heparin (Hook, M., Lindahl, U., Backstrom, G., Malmstrom, A., AND Fransson, L-A., J. Biol. Chem. (1974) 249, 3908). This conclusion was supported by the finding that no L[14C]iduronic acid could be detected in the UDP-hexuronic acid pool during this experiment. Nonsulfated and sulfated [14C]galactosaminoglycan products were degraded separately with chondroitinase-AC. The non-sulfated products afforded primarily disaccharide and a small amount of tetrasaccharide, while the sulfated products yielded, in addition, a considerable amount of larger oligosaccharides. Tetrasaccharides from nonsulfated products contained L-iduronic acid indicating that C-5 inversion at solitary sites can occur in the absence of sulfation of adjacent hexosamine moieties. The larger oligosaccharides obtained after chondroitinase-AC digestion of sulfated products yielded L-iduronic acid upon acid hydrolysis and were susceptible to chondroitinase-ABC digestion. The split products were almost exclusively 4-sulfated disaccharides. These results demonstrate that formation of blocks of L-iduronic acid-containing repeat periods is associated with 4-sulfation of adjacent hexosamine moieties.
mesh_terms: D002807:Chondroitin / Q000031:analogs & derivatives*; D003871:Dermatan Sulfate / Q000096:biosynthesis*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007067:Iduronic Acid / Q000096:biosynthesis*; D008861:Microsomes / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D010724:Phosphoadenosine Phosphosulfate / Q000378:metabolism; D011133:Polysaccharide-Lyases; D011134:Polysaccharides / Q000096:biosynthesis; D013464:Sulfuric Acids / Q000378:metabolism; D014535:Uridine Diphosphate Glucuronic Acid / Q000378:metabolism; D014536:Uridine Diphosphate N-Acetylgalactosamine / Q000378:metabolism; D014574:Uronic Acids / Q000096:biosynthesis*
chemical_list: D009844:Oligosaccharides; D011134:Polysaccharides; D013464:Sulfuric Acids; D014574:Uronic Acids; D003871:Dermatan Sulfate; D014535:Uridine Diphosphate Glucuronic Acid; D007067:Iduronic Acid; D010724:Phosphoadenosine Phosphosulfate; D014536:Uridine Diphosphate N-Acetylgalactosamine; D002807:Chondroitin; D011133:Polysaccharide-Lyases