Reactivity of a hereditary abnormal antithrombin III fraction in the inhibition of thrombin and factor Xa.
Two different AT-III fractions were purified from the plasma of a patient with recurrent superficial thrombophlebitis. The abnormal AT-III fraction (A-AT) was compared to the normal AT-III fraction (N-AT) in the inhibition of thrombin and factor Xa. Without heparin, both inactivate proteases in a similar manner and at the same rate. However, at low heparin concentration the thrombin inhibition proceeds more slowly with A-AT than with N-AT. At high heparin concentration the difference between A-AT and N-AT becomes very small. The inhibition of factor Xa follows a similar pattern. It is suggested that the heparin binding site of A-AT differs from that of N-AT resulting in a decreased heparin cofactor activity.
D000990:Antithrombin III / Q000235:genetics / Q000494:pharmacology*; D005170:Factor X / Q000037:antagonists & inhibitors*; D015951:Factor Xa; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D013917:Thrombin / Q000037:antagonists & inhibitors*
D000990:Antithrombin III; D005170:Factor X; D006493:Heparin; D013917:Thrombin; D015951:Factor Xa