Distribution of sulphate and iduronic acid residues in heparin and heparan sulphate

M. Hook, U. Lindahl, P. H. Iverius

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A method was developed for determination of the uronic acid composition of heparin like glycosaminoglycans. Polymers or oligosaccharides are degraded to monosaccharides by a combination of acid hydrolysis and deamination with HNO2. The resulting uronic acid monosaccharides (accounting for about 70% of the uronic acid contents of the starting materials) peptide isolated and converted into the corresponding aldono 1,4 lactones, which are separated by g.l.c. The calculated ratios of glucuronic acid/iduronic acid are reproducible within 5%. Samples of heparin from pig intestinal mucosa (molar ratio of sulphate/dissacharide unit, 2.40) and heparan sulphate from human aorta (sulphate/dissacharide ratio, 0.46) were subjected to uronic acid analysis. L Iduronic acid constituted 77% and 19% respectively of the total uronic acid contents. The correlation between the arg gly of sulphate and iduronic acid indicated by this finding also applied to the fractionated deamination products of the 2 polymers. The sulphated fragments varied in size from disaccharide to octasaccharide (or larger) and showed sulphate/disaccharide molar ratios in the range of 0.05 to 2.0. The proportion of iduronic acid increased with increasing ester sulphate contents of the oligosaccharides. Previous studies on the biosynthesis of heparin in a cell free system show that L iduronic acid residues are formed by C 5 epimerization of D glucuronic acid units at the polymer level and the process requires concomitant sulphation of the polymer. The results obtained in the present structural study conform to these findings, and suggest further that similar mechanisms may operate in the biosynthesis of heparan sulphate. The epimerization reaction appears to be linked to the sulphation of hydroxyl groups but does not seem to require sulphation of the target uronic acid residues. The significance of sulphamino groups in relation to the formation of iduronic acid is unknown.

Original languageEnglish (US)
Pages (from-to)33-43
Number of pages11
JournalBiochemical Journal
Issue number1
StatePublished - 1974

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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