There plasmin is a proteolytic enzyme, which belongs to the family of hydrolases, proteins capable of degrading other protein substances in the blood.
There plasmin it is precisely a serine protease, much more effective than trypsin as a hydrolytic activity, and is particularly effective in degrading the fibrin, a substance resulting from the degradation of fibrinogen and which forms thrombi in the bloodstream.
THE thrombi they are nothing but gods clots, clusters of fibrin fragments that block circulating blood cells such as white blood cells, red blood cells, platelets, and other circulating protein substances.
There plasmin is present in plasma in an inactive form (plasminogen), of a MW (molecular weight) of 83,500 Dalton; the conversion of plasminogen into plasmin occurs by activators such as plasma activators such as circulating thrombin, fibrin and factor XII or Hageman's factor, tissue activators such as tissue plasminogen activator (tPa) or plasminogen urokinase activator (uPa).
There plasmin catalyzes the hydrolysis of certain peptide bonds of fibrin and fibrinogen giving rise to soluble peptides and activates the complement system.
Plasmin is rendered inactive by numerous substances circulating in the serum of our body. The main inhibitors of plasmin are: alpha1-antitrypsin, antithrombin III, alpha2-antiplasmin and the serine protease inhibitor (serpin).
There are therefore no normal values of plasmin, since it is not present in an active form in the blood stream except in the presence of coagulation processes in place. Certainly the presence of wounds or states of increased consumption of coagulation factors such as disseminated intravascular coagulation (DIC) lead to a conspicuous production of plasmin with a consequent increase in blood values. To indirectly assess blood levels of plasmin, it is often used to measure the levels of its direct precursor, plasminogen.