Plasminogen is the precursor form of plasmin, the serine protease which degrades fibrin. It has a molecular weight of 92,000 and contains several domains, 5 kringle domains and a protease domain which is homologue to other serine proteaser like typsin and chymotrypsin. The N-terminal portion of the molecule consists of 77 positively charged amino acid residues. The kringle domains contain lysine binding sequences, which are often used in the purification of plasminogen, but in vivo bind plasminogen to fibrin. The concentration in plasma is 100-150 mg/L (highest among the fibrinolysis components) and t1/2 is 2 days. Plasminogen is converted to plasmin by t-PA or u-PA, by cleavage of the peptid bond between Arg561 and Val562.
Deficiency of plasminogen (hypoplasminogenemia and dysplasminogenemia) is associated with thromboembolism.
