| Summary: | The tributylammonium salt of whale ( Balaenoptera borealis L.) intestinal heparin with high affinity for antithrombin III, whose degrees of sulfate-substitution in D-glucosamine and L-iduronic acid residues are GlcNS 0.738, GlcN6S 0.384, and IdoA2S 0.510 mol, was reacted with 2.5, 5.0, or 10.0 mol of pyridine-sulfur trioxide/mol of available hydroxyl groups in iV.iV-dimethylformamide at – 10�C for 1 h. Both chemical and NMR spectroscopic analyses revealed that an exclusive 6- O -sulfation of the D-glucosamine residues proceeded, according to the amount of the sulfating reagent used (GlcNas: 0.476, 0.585, and 0.641 mol, respectively), the degree of sulfation at other natural substitution positions in the polysac-charide being unchanged, without any detectable unnatural sulfate-substitution. Biological examination of these products indicated that the 6-O-sulfation in the original whale heparin resulted in significant increases in blood clotting and anti-Factor Ha activities (maximal 43 and 82% increases, respectively), and in a moderate increase in the ability to bind antithrombin III, that is, in anti-Factor Xa activity and in intrinsic fluorescence enhancement of the protein (maximal 28 and 30% increases, respectively), together with a maximal 10% increase in the proportion of heparin species with higher affinity for antithrombin III, released with 1.0–3.0 M NaCl from antithrombin III-Sepharose.
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