plasminogeen

Plasminogeen, also known as plasminogen, is the zymogen of plasmin, a serine protease that drives fibrinolysis in the circulatory system. In humans it is predominantly synthesized by the liver and circulates in blood plasma as a single-chain glycoprotein of approximately 92 kDa. The molecule contains an N-terminal activation peptide, five kringle domains that mediate binding to lysine residues on fibrin and cell surfaces, and a C-terminal serine protease domain that becomes active upon proteolytic cleavage.

Activation is performed by tissue plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), which cleave plasminogen to form active plasmin. The activation is tightly regulated by inhibitors such as PAI-1 and PAI-2, and by α2-antiplasmin which inhibits plasmin activity.

Functionally, plasminogen and plasmin catalyze the breakdown of fibrin clots (fibrinolysis). When plasminogen is bound to fibrin, activation is focused at the clot, promoting efficient degradation. Plasmin also degrades other extracellular matrix components and can participate in tissue remodeling, wound healing, and inflammation by activating various proteases and growth factors.

Clinical relevance includes rare congenital plasminogen deficiencies, which cause ligneous conjunctivitis and other mucosal lesions due to abnormal fibrin deposition. Plasminogen levels can be affected by liver disease and coagulation disorders; dysregulation of the plasminogen–plasmin system is implicated in thrombotic and bleeding conditions.

Genetics: In humans, the PLG gene encodes plasminogen.