Biosynthesis of dermatan sulphate. Loss of C-5 hydrogen during conversion of D-glucuronate to L-iduronate.
The formation of L-iduronic acid during biosynthesis of dermatan sulphate has been studied in culture human fibroblasts and in microsomes from the same cells. The cells were incubated with D-[14C]glucose and D-[5-3H]glucose for 72 h. The [14C,3H]dermatan sulphate was hydrolysed and the disaccharides obtained were acetylated and separated by ion-exchange chromatography. The ratio of 3H/14C was 0.36 for N-acetyldermosine and 1.36 N-acetylchondrosine. A microsomal preparation from the fibroblasts was incubated with UDP-D-[5-3H]glucuronic acid, UDP-D-[14C]glucuronic acid, UDP-N-acetyl-D-galactosamine and 3'-phospho-5'-adenylyl sulphate. The polymeric products were separated into nonsulphated and sulphated components which had 3H/14C ratios of 0.51 and 0.20 and contained 9% and 70% of their uronosyl residues in the L-ido-configuration, respectively. Chondroitinase-AC digestion of these polymers liberated all of the remaining 3H activity. Hydrolysis and N-acetylation followed by paper chromatography showed that the L-iduronic acid-containing products were devoid of 3H. The data obtained indicate that the epimerization of D-glucuronosyl to L-iduronosyl residues during biosynthesis of dermatan sulphate involves an abstraction of the C-5 hydrogen of the uronosyl residue.
D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D002807:Chondroitin / Q000031:analogs & derivatives*; D002852:Chromatography, Ion Exchange; D003871:Dermatan Sulfate / Q000096:biosynthesis*; D005347:Fibroblasts / Q000378:metabolism; D005965:Glucuronates / Q000378:metabolism*; D020723:Glucuronic Acid; D006801:Humans; D007067:Iduronic Acid / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D013237:Stereoisomerism; D014316:Tritium; D014574:Uronic Acids / Q000378:metabolism*
D002250:Carbon Radioisotopes; D005965:Glucuronates; D014574:Uronic Acids; D014316:Tritium; D003871:Dermatan Sulfate; D007067:Iduronic Acid; D020723:Glucuronic Acid; D002807:Chondroitin