Structural diversity of N-sulfated heparan sulfate domains: distinct modes of glucuronyl C5 epimerization, iduronic acid 2-O-sulfation, and glucosamine 6-O-sulfation.
The N-sulfated regions (NS domains) represent the modified sequences of heparan sulfate chains and mediate interactions of the polysaccharide with proteins. We have investigated the relationship between the type/extent of polymer modification and the length of NS domains in heparan sulfate species from human aorta, bovine kidney, and cultured NMuMG and MDCK cells. C5 epimerization of D-glucuronic acid to L-iduronic acid was found to be extensive and essentially similar in all heparan sulfate species studied, regardless of domain size, whereas the subsequent 2-O-sulfation of the formed iduronic acid residues varies appreciably. In aorta heparan sulfate, up to 90% of the formed iduronate residues were 2-O-sulfated, whereas in kidney heparan sulfate 2-O-sulfation occurred only in </=50% of the iduronate residues. The degree of 2-O-sulfation was consistently increased with increasing NS domain length, suggesting a correlation between 2-O-sulfation efficiency and length of the polymeric substrate during heparan sulfate biosynthesis. By contrast, 6-O-sulfation of glucosamine units did not correlate to domain size. 6-O-Sulfation exceeded 2-O-sulfation in NS domains from kidney heparan sulfate, but was very low in aorta heparan sulfate. Remarkably, total O-sulfation of NS domains, i.e., the sum of 2-O- and 6-O-sulfate groups, was highly similar in all heparan sulfate samples investigated. The results reveal marked tissue-specific variation in the sulfation patterns of NS domains and indicate previously unrecognized distinctions in the coordination of the three polymer modification reactions during heparan sulfate biosynthesis.
Safaiyan
F
F
Department of Medical Biochemistry and Microbiology, Biomedical Center, Uppsala University, S-75123 Uppsala, Sweden.
Lindahl
U
U
Salmivirta
M
M
D000117:Acetylglucosamine / Q000378:metabolism; D000368:Aged; D000818:Animals; D002236:Carbohydrate Conformation; D002238:Carbohydrate Epimerases / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D002478:Cells, Cultured; D004187:Disaccharides / Q000302:isolation & purification / Q000378:metabolism; D004285:Dogs; D005944:Glucosamine / Q000378:metabolism*; D020723:Glucuronic Acid / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D006603:Hexuronic Acids / Q000378:metabolism; D006801:Humans; D007067:Iduronic Acid / Q000378:metabolism*; D008297:Male; D051379:Mice; D013329:Structure-Activity Relationship; D013431:Sulfates / Q000378:metabolism
D004187:Disaccharides; D019812:Heparan Sulfate Proteoglycans; D006603:Hexuronic Acids; D013431:Sulfates; D007067:Iduronic Acid; D020723:Glucuronic Acid; C000607178:glucuronic acid C5-epimerase, human; D002238:Carbohydrate Epimerases; D005944:Glucosamine; D000117:Acetylglucosamine