Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.2.2.7 (heparinase)
 1,270 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bovine antithrombin III (AT III) interaction with the luminal surface of bovine aortic segments with a continuous layer of endothelium was examined. Incubation of 125I-AT III with vessel segments, previously washed free of endogenous AT III, demonstrated specific, time-dependent binding to the protease inhibitor to the endothelium. Half-maximal binding was observed at an added AT III concentration of 14 nM. Binding of 125I-AT III to the vessel wall was reversible (50% dissociated in 4 min), and addition of either heparin or Factor Xa accelerated displacement of 125I-AT III from the vessel segment. Dissociation of 125I-AT III from the vessel segment in the presence of factor Xa coincided with the formation of a Factor Xa-125I-AT III complex. Inactivation of Factor IXa and Factor Xa by AT III was facilitated in the presence of vessel segments. Pretreatment of vessel segments with highly purified Flavobacterium heparinase precluded the vessel-dependent augmentation of AT III anticoagulant activity as well as specific binding of 125I-AT III to the vessel endothelium. In contrast, pretreatment of the vessel segments with chrondroitinases (ABC or AC) had no detectable effect on 125I-AT III binding or on AT III anticoagulant activity. AT III binding to vessel segments was competitively inhibited by increasing concentration of platelet factor 4. Binding of the protease inhibitor to vessel segments was inhibited by chemical modification of AT III lysyl or tryptophan residues. These AT III derivatives retained progressive inhibitory activity. These data suggest that heparin-like molecules are present on the aortic vessel wall and mediate binding of AT III to the vessel surface, as well as enhancing the anticoagulant activity of AT III at these sites.
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PMID:Interaction of antithrombin III with bovine aortic segments. Role of heparin in binding and enhanced anticoagulant activity. 396 7

Cultured microvascular endothelial cells isolated from rat epididymal fat pads produce glycosaminoglycans that accelerate thrombin-antithrombin complex formation. The heparinlike nature of these macromolecules was established by complete destruction of their anticoagulant activity employing purified Flavobacterium heparinase. Only 15% of the biologic activity of these complex carbohydrates was expressed when the heparin binding domain on the protease inhibitor was chemically modified at the Trp 49 residue. The anticoagulantly active species contains disaccharides which constitute the unique antithrombin binding region of the mucopolysaccharide. Removal of the biologically active heparinlike components from endothelial cells with 0.05% trypsin suggests that these molecular species are present on the cell surface.
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PMID:Heparinlike molecules with anticoagulant activity are synthesized by cultured endothelial cells. 397 Jun 99

We have isolated from nitrous acid cleavage products of heparin two major octasaccharide fragments which bind with high affinity to human antithrombin. Octasaccharide S, with the predominant structure iduronic acid----N-acetylglucosamine 6-O-sulfate----glucuronic acid-----N-sulfated glucosamine 3,6-di-O-sulfate----iduronic acid 2-O-sulfate----N-sulfated glucosamine 6-O-sulfate----iduronic acid 2-O-sulfate----anhydromannitol 6-O-sulfate, is sensitive to cleavage by Flavobacterium heparinase as well as platelet heparitinase and binds to antithrombin with a dissociation constant of (5-15) X 10(-8) M. Octasaccharide R, with the predominant structure iduronic acid 2-O-sulfate----N-sulfated glucosamine 6-O-sulfate----iduronic acid----N-acetylglucosamine 6-O-sulfate----glucuronic acid----N-sulfated glucosamine 3,6-di-O-sulfate----iduronic acid 2-O-sulfate----anhydromannitol 6-O-sulfate, is resistant to degradation by both enzymes and binds antithrombin with a dissociation constant of (4-18) X 10(-7) M. The occurrence of a 15-17% replacement of N-sulfated glucosamine 3,6-di-O-sulfate with N-sulfated glucosamine 3-O-sulfate and a 10-12% replacement of iduronic acid with glucuronic acid in both octasaccharides indicates that these substitutions have little or no effect on the binding of the oligosaccharides to the protease inhibitor. When bound to antithrombin, both octasaccharides produce a 40% enhancement in the intrinsic fluorescence of the protease inhibitor and a rate of human factor Xa inhibition of 5 X 10(5) M-1 s-1 as monitored by stopped-flow fluorometry. This suggests that the conformation of antithrombin in the region of the factor Xa binding site is similar when the protease inhibitor is complexed with either octasaccharide.
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PMID:Sequence variation in heparin octasaccharides with high affinity for antithrombin III. 652 37

We have examined the role of heparinlike molecules in the regulation of coagulation by perfusing rat hindquarters with purified human thrombin and with its plasma inhibitor, antithrombin. Our data indicate that contact of the hemostatic components with the endothelium enhances the rate of thrombin-antithrombin complex formation by as much as 19-fold over the uncatalyzed rate of enzyme-inhibitor interaction. Heparinlike molecules are responsible for the antithrombin accelerating activity. The amount of thrombin-antithrombin complex generated within the hindlimb preparation after pretreatment of the vasculature with purified Flavobacterium heparinase or with addition of platelet Factor IV to the hemostatic components, was equal to the uncatalyzed levels. These heparinlike molecules appear to be tightly bound to the luminal surface of the endothelium, since they could not be detected within the physiologic buffer that was perfused through the animal. The above mucopolysaccharides function in a manner similar to commercial heparin, since modification of antithrombin at a site critical for heparin-dependent acceleration of the protease inhibitor resulted in a level of interaction product identical to the uncatalyzed amount. Finally, addition of diisofluorophosphate-thrombin to the enzyme perfusion stream reduced the amount of thrombin-antithrombin complex formed in the animal by 30-40%, which suggested that thrombin bound to the endothelium as well as enzyme free in solution are accessible to antithrombin that has interacted with heparinlike molecules present on the endothelium.
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PMID:Acceleration of thrombin-antithrombin complex formation in rat hindquarters via heparinlike molecules bound to the endothelium. 674 97