Antithrombin
& Heparin
Unfractionated or therapeutic
heparin:
Types of heparin:
Low molecular weight heparin:
Mechanism of
heparin action on AT:
Contains >17 sugar
units
Contains <17 sugar
units
Heparin molecule binds both AT and
thrombin to its surface bringing them into close approximation with each other. Process of
“approximation”
Therapeutic heparin increases rate
of thrombin neutralization by AT by a factor of 1000
AT then neutralizes thrombin to
forming a TAT complex which is removed by the RES
Low molecular weight heparin is able
to bind AT and alter it so it can neutralize Xa but does not cause “approximation with thrombin &
AT
