The protein encoded by this gene is a plasma protease
inhibitor and a member of the serpin superfamily. This protein
inhibits thrombin as well as other activated serine proteases of
the coagulation system, and it regulates the blood coagulation
cascade. The protein includes two functional domains: the heparin
binding-domain at the N-terminus of the mature protein, and the
reactive site domain at the C-terminus. The inhibitory activity is
enhanced by the presence of heparin. More than 120 mutations have
been identified for this gene, many of which are known to cause
antithrombin-III deficiency.
