Antithrombin III:
A plasma alpha 2 glycoprotein that accounts for the major antithrombin activity of normal plasma and also inhibits several other enzymes; it was formerly called Antithrombin II (AT II) which has now been shown to be identical to AT III; deficiency of AT III (ANTITHROMBIN III DEFICIENCY), hereditary or acquired, results in thromboembolism. It is a member of the serpin superfamily. Some authors use the term antithrombin to refer to antithrombin III.
