Antithrombin

Function

Antithrombin (AT) inactivates several enzymes of the coagulation cycle. AT is relatively inactive until it binds the heparan sidechains of the microvasculature.^[1]
▪ α-AT contains 4 occupied glycosylation sites and is found in blood palsma.
▪ β-AT contains only 3 occupied glycosylation sites.
▪ AT-I refers to the absorption of thrombin to fibrin.
▪ AT-II and heparin interfere with the interaction of thrombin and fibrinogen.
▪ AT-III inactivates thrombin in plasma. For details see Student Projects for UMass Chemistry 423 Spring 2012-7.
▪ AT-IV becomes activated during blood coagulation.
See details for the antithrombin pentasaccharide complex in Molecular Playground/Antithrombin-Heparin.

Disease

AT deficiency diseases are: Acquired AT deficiency and Inherited AT deficiency. AT deficiency is involved in thrombosis and pulmonary embolism.

Relevance

AT activity is enhanced upon .

Structural highlights

The binding of AT to the heparans or the heparin drug is to a core pentasaccharide. The binding induces conformational change of AT.