Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed from fibrinogen by the protease thrombin, and is then polymerised to form a “mesh” that forms a hemostatic plug or clot (in conjunction with platelets) over a wound site.
Fibrin is involved in signal transduction, blood coagulation, and platelet activation.
A protease (also termed peptidase or proteinase) is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein.
Thrombin is a “trypsin-like” serine protease protein that in humans is encoded by the F2 gene. Prothrombin (coagulation factor II) is proteolytically cleaved to form thrombin in the coagulation cascade, which ultimately results in the stemming of blood loss. Thrombin in turn acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin, as well as catalyzing many other coagulation-related reactions.
The activity of proteases is inhibited by protease inhibitors. One example of protease inhibitors is the serpin superfamily, which includes alpha 1-antitrypsin, C1-inhibitor, antithrombin, alpha 1-antichymotrypsin, plasminogen activator inhibitor-1, and neuroserpin.
Natural protease inhibitors include the family of lipocalin proteins, which play a role in cell regulation and differentiation. Lipophilic ligands, attached to lipocalin proteins, have been found to possess tumor protease inhibiting properties. The natural protease inhibitors are not to be confused with the protease inhibitors used in antiretroviral therapy. Some viruses, with HIV/AIDS among them, depend on proteases in their reproductive cycle. Thus, protease inhibitors are developed as antiviral means.
The study of protease inhibitors could lead to a breakthru in the knowledge of fribinogen, which is essential in the clotting of blood, the missing gene factors of a person with this disease compared to a normal person, and the breakdown of molecules found in fribinogen, will unlock all the keys. If you could reverse engineer the protease inhibitors, you could in fact produce fribinogen, but no knowledge is available at present.
– Contributed by Oogle