Plasma Anticoagulant Mechanisms of Heparin, Heparan Sulfate, and Dermatan Sulfatea

The relationship between two anticoagulant actions of glycosaminoglycans (GAGs), namely the catalysis of thrombin inhibition (assessed by thrombin-antithrombin-III and thrombin-heparin-cofactor-II formation) and the inhibition of prothrombin activation, was explored by comparing the effects of heparin, heparan sulfate, and dermatan sulfate on the two reactions in plasma. Heparan sulfate and dermatan sulfate were also resulfated in vitro to yield products with sulfate/carboxylate ratios similar to those of heparin. Their effects on thrombin inhibition and the activation of prothrombin were also determined. The catalytic efficiency of the five GAGs on thrombin inhibition and their inhibitory effects on prothrombin activation decreased in the following order: heparin; resulfated dermatan sulfate; resulfated heparan sulfate; heparan sulfate = dermatan sulfate. These results suggest that the catalytic efficiency of a glycosaminoglycan on thrombin inhibition translates to its inhibitory effect on prothrombin activation, since catalysis of thrombin inhibition results in the inhibition of the thrombin-dependent positive feedback reactions of coagulation which facilitate prothrombinase formation.