LMWH: Mechanism of action

LMWH binds to anti-thrombin, a serine protease inhibitor, and creates a conformational change. This change accelerates itsinhibition of activated factor Xin conversion of prothrombin to thrombin. Thus,thrombin cannot convert fibrinogen to fibrin strands and clot formation. Once this change occurs LMWH is freed and can bind to another anti-thrombin molecules. LMWH also directly inhibits thrombin as it is a heterogenous mixture of molecules, some containing enough polysaccharide sequence, but this effect is much less than that of unfractionated heparin.