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Plasmin
 
 
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Plasmin is an important enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
  present in blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
 that degrades many blood plasma
Blood plasma

Blood plasma is the liquid component of blood, in which the blood cells are suspended. It makes up about 55% of total blood volume. It is composed of mostly water , and contains dissolved proteins, glucose, clotting factors, mineral ions, Hormone and carbon dioxide ....
 proteins, most notable, fibrin
Fibrin

Fibrin is a fibrous protein involved in the clotting of blood, and is non globular. It is a fibrillar protein that is Polymerization to form a "mesh" that forms a hemostasis plug or clot over a wound site....
 clot
Thrombus

A thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system ....
s. The degradation of fibrin is termed fibrinolysis
Fibrinolysis

Fibrinolysis is the process wherein a fibrin thrombus, the product of coagulation, is broken down. Its main enzyme plasmin cuts the fibrin mesh at various places, leading to the production of circulating fragments that are cleared by other proteases or by the kidney and liver....
. In humans, the plasmin protein is encoded by the PLG gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
.

minogen (PLG) is a circulating zymogen
Zymogen

A zymogen is an inactive enzyme Protein precursor. A zymogen requires a biochemical change for it to become an active enzyme. The biochemical change usually occurs in a lysosome where a specific part of the precursor enzyme is cleaved in order to activate it....
 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
Urokinase

Urokinase , also called urokinase-type Plasminogen Activator , is a serine protease . Urokinase was originally isolated from human urine, but is present in several physiological locations, such as blood stream and the extracellular matrix....
 and tissue plasminogen activator
Tissue plasminogen activator

Tissue plasminogen activator is a protein involved in the breakdown of blood clots. Specifically, it is a serine protease found on endothelial cells, the cells that line the blood vessels....
.






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Encyclopedia


Plasmin is an important enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
  present in blood
Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
 that degrades many blood plasma
Blood plasma

Blood plasma is the liquid component of blood, in which the blood cells are suspended. It makes up about 55% of total blood volume. It is composed of mostly water , and contains dissolved proteins, glucose, clotting factors, mineral ions, Hormone and carbon dioxide ....
 proteins, most notable, fibrin
Fibrin

Fibrin is a fibrous protein involved in the clotting of blood, and is non globular. It is a fibrillar protein that is Polymerization to form a "mesh" that forms a hemostasis plug or clot over a wound site....
 clot
Thrombus

A thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system ....
s. The degradation of fibrin is termed fibrinolysis
Fibrinolysis

Fibrinolysis is the process wherein a fibrin thrombus, the product of coagulation, is broken down. Its main enzyme plasmin cuts the fibrin mesh at various places, leading to the production of circulating fragments that are cleared by other proteases or by the kidney and liver....
. In humans, the plasmin protein is encoded by the PLG gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
.

Function

Plasminogen (PLG) is a circulating zymogen
Zymogen

A zymogen is an inactive enzyme Protein precursor. A zymogen requires a biochemical change for it to become an active enzyme. The biochemical change usually occurs in a lysosome where a specific part of the precursor enzyme is cleaved in order to activate it....
 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
Urokinase

Urokinase , also called urokinase-type Plasminogen Activator , is a serine protease . Urokinase was originally isolated from human urine, but is present in several physiological locations, such as blood stream and the extracellular matrix....
 and tissue plasminogen activator
Tissue plasminogen activator

Tissue plasminogen activator is a protein involved in the breakdown of blood clots. Specifically, it is a serine protease found on endothelial cells, the cells that line the blood vessels....
. The main function of plasmin is to dissolve fibrin
Fibrin

Fibrin is a fibrous protein involved in the clotting of blood, and is non globular. It is a fibrillar protein that is Polymerization to form a "mesh" that forms a hemostasis plug or clot over a wound site....
 blood clots. Plasmin, like trypsin
Trypsin

Trypsin is a serine protease found in the digestive system, where it breaks down proteins. Trypsin predominantly cleaves peptide chains at the carboxyl side of the amino acids lysine and arginine, except when either is followed by proline....
, belongs to the family of serine protease
Serine protease

Serine proteases or serine endopeptidases are proteases in which one of the amino acids at the active site is serine.They are found in both single-cell and complex organisms, in both cells with nuclei and without nuclei ....
s.

It is a serine protease
Serine protease

Serine proteases or serine endopeptidases are proteases in which one of the amino acids at the active site is serine.They are found in both single-cell and complex organisms, in both cells with nuclei and without nuclei ....
 that is released as plasminogen from the liver into the circulation and activated by tissue plasminogen activator
Tissue plasminogen activator

Tissue plasminogen activator is a protein involved in the breakdown of blood clots. Specifically, it is a serine protease found on endothelial cells, the cells that line the blood vessels....
 (tPA), urokinase plasminogen activator (uPA), thrombin
Thrombin

Thrombin is a coagulation protein that has many effects in the coagulation#The_coagulation_cascade. It is a serine protease that converts soluble fibrinogen into insoluble strands of fibrin, as well as catalyzing many other coagulation-related reactions....
, fibrin
Fibrin

Fibrin is a fibrous protein involved in the clotting of blood, and is non globular. It is a fibrillar protein that is Polymerization to form a "mesh" that forms a hemostasis plug or clot over a wound site....
, and factor XII
Factor XII

Hageman factor is a plasma protein also known as factor XII. It is the zymogen form of factor XIIa, an enzyme of the serine protease class....
 (Hageman factor). It is inactivated by alpha 2-antiplasmin
Alpha 2-antiplasmin

Alpha 2-antiplasmin is a serine protease inhibitor responsible for inactivating plasmin, an important enzyme that participates in fibrinolysis and degradation of various other proteins....
, a serine protease inhibitor (serpin).

Apart from fibrinolysis, plasmin proteolyses
Proteolysis

Proteolysis is the directed degradation of proteins by cellular enzymes called proteases or by intramolecular digestion....
 proteins in various other systems: It activates collagenases, some mediators of the complement system
Complement system

The complement system is a biochemical cascade that helps clear pathogens from an organism. It is part of the larger immune system that is not adaptable and does not change over the course of an individual's lifetime; as such it belongs to the innate immunity....
 and weakens the wall of the Graafian follicle (leading to ovulation
Ovulation

Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum that participates in reproduction....
). It cleaves fibrin
Fibrin

Fibrin is a fibrous protein involved in the clotting of blood, and is non globular. It is a fibrillar protein that is Polymerization to form a "mesh" that forms a hemostasis plug or clot over a wound site....
, fibronectin
Fibronectin

Fibronectin is a high-molecular weight extracellular matrix glycoprotein that binds to cell membrane-spanning receptor proteins called integrins....
, thrombospondin
Thrombospondin

Thrombospondins are secreted proteins with antiangiogenic abilities....
, laminin, and von Willebrand factor
Von Willebrand factor

Von Willebrand factor is a blood glycoprotein involved in hemostasis. It is deficient or defective in von Willebrand disease and is involved in a large number of other diseases, including thrombotic thrombocytopenic purpura, Heyde's syndrome, and possibly hemolytic-uremic syndrome....
.

Apart from fibrinolysis, plasminogen is shown to play important role in wound healing, liver repair as well as the mantainance of liver homeostasis.

Fibrinolysis

Pathology

Deficiency in plasmin may lead to thrombosis
Thrombosis

Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot, because the first step in repairing it is to prevent loss of blood....
, as clots are not degraded adequately. Plasminogen deficiency in mice leads to defective wound healing, defective liver repair, reproductive abnormalities.

Further reading


External links