Blood coagulation is healthy and lifesaving because it can stop bleeding. It
can, however, be a troublemaker as well, causing serious medical problems including heart attack and stroke. Body has
complex blood coagulation cascade to modulate the blood clots. In the environment of plasma, the blood coagulation cascade
is regulated by antithrombin, which is deemed one of the most important serine protease inhibitors. It inhibits thrombin;
it can inhibit factors IXa and Xa as well. Interestingly, its inhibitory ability will be significantly increased with the existence
of heparin. In this minireview paper, we are to summarize the structural features of antithrombin, as well as its
heparin binding modes and anti-coagulation mechanisms, in hopes that the discussion and analysis presented in this paper
can stimulate new strategies to find more effective approaches or compounds to modulate the antithrombin.