Coagulation factor II (Thrombin) (F2)

Coagulation factor II, commonly known as thrombin, is a multifunctional serine protease that plays a central role in hemostasis by converting fibrinogen into fibrin and stimulating platelet aggregation (UniProt: P00734) [1]. The designation "Thrombin via antithrombin" describes a therapeutic strategy where thrombin's enzymatic activity is neutralized indirectly through the activation of antithrombin III (ATIII), a natural circulating anticoagulant (StatPearls: Heparin) [2]. Drugs such as unfractionated heparin bind to ATIII, causing a conformational change and acting as a catalytic template that accelerates the inactivation of thrombin by ATIII by up to 1,000-fold (DrugBank: DB01109) [3]. This mechanism is clinically leveraged to prevent and treat various thromboembolic conditions, including deep vein thrombosis, pulmonary embolism, and myocardial infarction (PubMed: PMID 25660360) [4]. Because this pathway relies on an endogenous cofactor, its efficacy can be influenced by ATIII deficiency, and it requires careful monitoring of coagulation parameters to mitigate the risk of major hemorrhage or heparin-induced thrombocytopenia [2]. Unlike direct thrombin inhibitors, which bind the active site of thrombin independently, this indirect approach is highly dependent on the availability of antithrombin and the chain length of the heparinoid used [3].

Other names

ThrombinFactor IIaProthrombinActivated factor IIAntithrombin-dependent thrombin inhibition

Indirect inhibition of thrombin through the allosteric activation of antithrombin III and template-mediated bridging.