Plasmin
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Plasmin is an important enzyme (EC 3.4.21.7) present in blood that degrades many blood plasma proteins, most notable, fibrin clots. The degradation of fibrin is termed fibrinolysis. In humans, the plasmin protein is encoded by the PLG gene.[1]
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[edit] Function
Plasminogen (PLG) is a circulating zymogen that is converted to the active enzyme plasmin by cleavage of the peptide bond between Arg-560 and Val-561, which is mediated by urokinase and tissue plasminogen activator. The main function of plasmin is to dissolve fibrin blood clots. Plasmin, like trypsin, belongs to the family of serine proteases.[1][2][3]
Plasmin is a serine protease that is released as plasminogen from the liver into the circulation and activated by tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), and factor XII (Hageman factor). Fibrin is a cofactor for plasminogen activation by tissue plasminogen activator. Urokinase plasminogen activator receptor (uPAR) is a cofactor for plasminogen activation by urokinase plasminogen activator. Plasmin is inactivated by alpha 2-antiplasmin, a serine protease inhibitor (serpin).
Apart from fibrinolysis, plasmin proteolyses proteins in various other systems: It activates collagenases, some mediators of the complement system and weakens the wall of the Graafian follicle (leading to ovulation). It cleaves fibrin, fibronectin, thrombospondin, laminin, and von Willebrand factor.
Apart from fibrinolysis, plasminogen is shown to play important role in wound healing, liver repair as well as the mantainance of liver homeostasis.
[edit] Pathology
Deficiency in plasmin may lead to thrombosis, as clots are not degraded adequately. Plasminogen deficiency in mice leads to defective wound healing, defective liver repair, reproductive abnormalities.[citation needed]
[edit] References
- ^ a b "Entrez Gene: plasminogen". http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=5340.
- ^ Miyata T, Iwanaga S, Sakata Y, Aoki N (October 1982). "Plasminogen Tochigi: inactive plasmin resulting from replacement of alanine-600 by threonine in the active site". Proc. Natl. Acad. Sci. U.S.A. 79 (20): 6132–6. doi:. PMID 6216475. PMC: 347073. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=6216475.
- ^ Forsgren M, Råden B, Israelsson M, Larsson K, Hedén LO (March 1987). "Molecular cloning and characterization of a full-length cDNA clone for human plasminogen". FEBS Lett. 213 (2): 254–60. doi:. http://linkinghub.elsevier.com/retrieve/pii/0014-5793(87)81501-6.
[edit] Further reading
- Shanmukhappa K, Mourya R, Sabla GE, Degen JL, Bezerra JA (July 2005). "Hepatic to pancreatic switch defines a role for hemostatic factors in cellular plasticity in mice". Proc. Natl. Acad. Sci. U.S.A. 102 (29): 10182–7. doi:. PMID 16006527.
- Anglés-Cano E, Rojas G (2003). "Apolipoprotein(a): structure-function relationship at the lysine-binding site and plasminogen activator cleavage site". Biol. Chem. 383 (1): 93–9. doi:. PMID 11928826.
- Ranson M, Andronicos NM (2004). "Plasminogen binding and cancer: promises and pitfalls". Front. Biosci. 8: s294–304. doi:. PMID 12700073.
[edit] External links
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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