Antithrombin-mediated Anticoagulant Activity of Sulfated Polysaccharides

Abstract

We investigated the mechanisms of anticoagulant activity mediated by sulfated galactans. The anticoagulant activity of sulfated polysaccharides is achieved mainly through potentiation of plasma cofactors, which are the natural inhibitors of coagulation proteases. Our results indicated the following. 1) Structural requirements for the interaction of sulfated galactans with coagulation inhibitors and their target proteases are not merely a consequence of their charge density. 2) The structural basis of this interaction is complex because it involves naturally heterogeneous polysaccharides but depends on the distribution of sulfate groups and on monosaccharide composition. 3) Sulfated galactans require significantly longer chains than heparin to achieve anticoagulant activity. 4) Possibly, it is the bulk structure of the sulfated galactan, and not a specific minor component as in heparin, that determines its interaction with antithrombin. 5) Sulfated galactans of ϳ15 to ϳ45 kDa bind to antithrombin but are unable to link the plasma inhibitor and thrombin. This last effect requires a molecular size above 45 kDa. 6) Sulfated galactan and heparin bind to different sites on antithrombin. 7) Sulfated galactans are less effective than heparin at promoting antithrombin conformational activation. Overall, these observations indicate that a different mechanism predominates over the conformational activation of antithrombin in ensuring the antithrombin-mediated anticoagulant activity of the sulfated galactans. Possibly, sulfated galactan connects antithrombin and thrombin, holding the protease in an inactive form. The conformational activation of antithrombin and the consequent formation of a covalent complex with thrombin appear to be less important for the anticoagulant activity of sulfated galactan than for heparin. Our results demonstrate that the paradigm of heparin-antithrombin interaction cannot be extended to other sulfated polysaccharides. Each type of polysaccharide may form a particular complex with the plasma inhibitor and the target protease.

Structure versus anticoagulant and antithrombotic actions of marine sulfated polysaccharides

“…With the examples described throughout the text, it is clear that the template mechanisms between SP (SF, SG, GAG), serpins (AT, HC-II) and protease (IIa) have differential stabilities or formation kinetics that are directly related to the structural features of the SP. and fully supports the expected bridging mechanism for the activity of SG, as previously described (Melo et al, 2004). Thus, both compounds are capable of interacting with AT, as indicated by theoretical results and experimental data showing that both polysaccharides are retained on an AT-affinity column.…”

“…Anticoagulant activities of MSPs measured by APTT a and by IC50 for thrombin (IIa) and factor Xa inhibition in the presence of antithrombin (AT) or Heparin Cofactor II (HCII) (Pavão et al, 1998;Mourão, 2004;Pereira et al, 2005;Fonseca et al, 2008 Pavão et al, 1998. complex between heparin-AT-IIa ( Figure 4A), which supports the potentiation of this protease inactivation by AT in the presence of SG. This is an example of how the orientational constraints in solution can influence spatial preferences of the SP for their different bindings with target proteins (Melo et al, 2004). It is obvious that the difference in the sugar type drastically changes the conformation of the polymer as well, implying a different conformational binding, as explained in this section.…”

Effect of Sulfation on the Structure and Anticoagulant Activity of Ulvan Extracted From Green Seaweed Ulva Reticulata

“…The results of anticoagulant activity indicated that the increasing of sulfate content from 15.04 % for UR to 25.68 % for URS resulting in an increasing of bioactivity. Melo et al [13] reported that the introduction of sulfate to polysaccharides increases the amount of negative charge. Then, the negatively charged sulfate groups can be combined with the positively charged groups from the coagulation protease inhibitor antithrombin, which can activate antithrombin and produce anticoagulant activity.…”

“…The results of 1 H và 13 C-NMR analysis were summarized in Table 1. The presence of sulfate groups after sulfation process was confirmed by FTIR and NMR spectra.…”

Anticoagulant Activity and Structural Characterization of Polysaccharide from Abalone (Haliotis discus hannai Ino) Gonad

“…Furthermore, the incidence of prion-related diseases in cows means that bovine heparin runs a risk of contamination which has to be carefully monitored. In the meantime, the ever-increasing demand for antithrombotic therapy calls for alternative sources of anticoagulant and antithrombotic compounds [8]. It has been shown that sulfated polysaccharides with anticoagulant activity are most abundant in marine invertebrates and marine algae [9,10].…”