Plasminogen activator inhibitor-2 (placental PAI) is a coagulation

Coagulation

Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...

 factor that inactivates tPA

Tissue plasminogen activator

Tissue plasminogen activator is a protein involved in the breakdown of blood clots. It is a serine protease found on endothelial cells, the cells that line the blood vessels. As an enzyme, it catalyzes the conversion of plasminogen to plasmin, the major enzyme responsible for clot breakdown...

 and 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...

. It is present in most cells, especially monocytes/macrophages. PAI-2 exists in two forms, a 60-kDa extracellular glycosylated form and a 43-kDa intracellular form.

It is present only at detectable quantities in blood during pregnancy

Pregnancy

Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

, as it is produced by the placenta

Placenta

The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

, and may explain partially the increased rate of 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 to prevent blood loss...

 during pregnancy. The majority of expressed PAI-2 remains unsecreted due to the presence of an inefficient internal signal peptide.

Interactions

Plasminogen activator inhibitor-2 (SerpinB2) has been reported to bind a series of intracellular and extracellular proteins. Whether SerpinB2's physiological function is inhibition of the extracellular protease urokinase and/or whether SerpinB2 has intracellular activities remains controversial. At least one of SerpinB2's physiological functions may involve regulation of adaptive immunity. Reviewed in Schroder WA, Major L, Suhrbier A. The role of SerpinB2 in immunity. Crit Rev Immunol. 2011;31(1):15-30. PMID: 21395508.

Further reading

External links

• The MEROPS
  Merops
  Merops may refer to:* Merops , a genus of bee-eaters.* MEROPS, an on-line database for peptidases.It may also refer to several figures from Greek mythology:* King of Ethiopia, husband of Clymene, who lay with Helios and bore Phaethon...
  
  online database for peptidases and their inhibitors: I04.007