Samples of heparan sulfate, isolated from bovine aorta, lung, intestine, and kidney, were degraded by digestion with a mixture of heparitinases or by treatment with nitrous acid, with or without previous Ndeacetylation. Analysis of the resulting oligosaccharides showed that the various heparan sulfate samples all contained regions of up to 8 or 9 consecutive Nacetylated glucosamine residues, as well as contiguous N-sulfated sequences. L-Iduronic acid accounted for a remarkably constant proportion, 50 -60%, of the total hexuronic acid units within the latter structures. Of the total iduronic acid units, 36 -55% were located outside the contiguous N-sulfated regions, presumably in sequences composed of alternating N-acetylated and Nsulfated disaccharide residues. While most of the iduronic acid units within the N-sulfated blocks were 2-Osulfated, those located outside were almost exclusively nonsulfated. The heparan sulfate preparations differed markedly with regard to the content of 6-O-sulfated glucosamine units, more than half of which were located outside the N-sulfated block regions. These findings suggest that the formation of iduronic acid residues and their subsequent 2-O-sulfation are coupled within but not outside the contiguous N-sulfated regions of the heparan sulfate chains and, furthermore, that the 2-Oand 6-O-sulfotransferase reactions are differentially regulated during heparan sulfate biosynthesis.

No abstract

No abstract

No abstract