Proteinase nexin

Heparin cofactor II, when activated by binding to glycosaminoglycans (dermatan sulfate, heparins, and heparin), inhibits thrombin (24). The 43-kDa serpin, proteinase nexin 1, possesses 30% sequence homology with ATIII and can be activated by binding to heparin to inhibit several serine proteinases including thrombin (25). Proteinase nexin 2 is found within the platelet a-granule and is released when platelets are activated (26). It is able to inhibit factor XIa. 

Other plasminogen activator inhibitors are PAI-3, which is believed to be identical to the activated protein C inhibitor, and proteinase nexin 1, found in the renal epithelial cells, cytosol of fibroblasts, and cardiac myocytes (37, 42, 44, 45). 

Another serine protease inhibitor of the al-antitrypsin family (serpin) is heparin cofactor II (HCII), which also forms a 1 1 complex with thrombin, but does not react with factor Xa [4,10]. The rate of inhibition of thrombin is not only increased by heparinoids but also by the related glycosaminoglycan dermatan sulfate. The identification of an inhibitor variant and site-directed mutagenesis studies on HC II cDNA led to the understanding that the binding sites for heparin and dermatan sulfate may be overlapping but not identical. Further proteinase inhibitors interacting with heparinoids are tissue factor pathway inhibitor and protease nexin-1. 

PLAT Plasminogen activator, tissue serine (or cysteine) proteinase inhibitor, Clade E (nexin, plasminogen activator inhibitor type 1), member 1... 

Since aiAT represents the archetype for the serpin (serine-proteinase inhibitor) superfamily of proteins, it is possible that similar oxidative or proteolytic mechanisms may function in the inactivation of other serpins that are important in controlling the inflammatory cascade. Some serpins contain a readily oxidised reactive-centre methionine residue (e.g. plasminogen activator-inhibitor [108] and a2-antiplasmin [109]), whilst all serpins (including antithrombin III [110] and protease nexin I [111]) contain an exposed loop which is susceptible to cleavage by proteinases. 

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