Plasmin is the main enzyme in fibrinolysis, which breaks down fibrin.

Alpha-2-antiplasmin is an inhibitor of serine proteases, mainly plasmin. It plays an important role in the regulation of fibrinolysis. A decrease in the amount of alpha-2-antiplasmin can lead to bleeding syndromes.

Alpha-2-antiplasmin reacts rapidly to plasmin to form a PAP complex. An increase in the formation of the PAP complex is accompanied by an increase in the formation of fibrin and an increase in the level of reactive plasmin.
There is a correlation between the level of fibrin fragment and the level of PAP complex.