title: Isoform composition of antithrombin in a covalent antithrombin-heparin complex.
abstract: Antithrombin (AT) circulates in two isoforms, alpha- (90-95%) and beta-AT (5-10%). AT inhibits clotting factors such as thrombin and factor Xa, a reaction catalyzed by heparin. Heparin has been used in many clinical situations but suffers from limitations such as a short intravenous half-life, bleeding risk, and the inability to inhibit thrombin bound to fibrin clots. In order to overcome some of heparin's limitations, we prepared a covalent AT-heparin complex (ATH) that has increased intravenous half-life, reduced bleeding risk, and can directly inhibit clot-bound thrombin. However, structural analysis is required to further develop this promising antithrombotic agent. It was found that the proportion of isoforms in ATH (55% alpha-AT, and 45% beta-AT) was significantly different than that in the commercial AT starting material (80% alpha-AT and 20% beta-AT). Further analysis of the rate of heparin-catalyzed inhibition of thrombin by AT isoforms prepared from ATH revealed that the beta-variant reacted approximately 2-fold faster.
mesh_terms: D000991:Antithrombins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism*
chemical_list: D000991:Antithrombins; D020033:Protein Isoforms; D006493:Heparin