Alpha 2-antiplasmin

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Template:Short description Template:Cs1 config Template:Infobox gene Alpha 2-antiplasmin (or α2-antiplasmin or plasmin inhibitor) is a serine protease inhibitor (serpin) responsible for inactivating plasmin.<ref>Template:Cite journal</ref> Plasmin is an important enzyme that participates in fibrinolysis and degradation of various other proteins. This protein is encoded by the SERPINF2 gene.<ref name="entrez">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Fibrinolysis (simplified). Blue arrows denote stimulation, and red arrows inhibition.

Structure

Alpha 2-antiplasmin (α2AP) is a member of the serine protease inhibitor (serpin) superfamily and is structurally characterized by a central serpin domain flanked by unique N- and C-terminal extensions.<ref name = "Holmes_1987">Template:Cite journal</ref><ref name = "Singh_2020">Template:Cite journal</ref> The mature human α2AP protein consists of 452 amino acids, with a 12-residue N-terminus, a central serpin domain, and a C-terminal tail of approximately 55 residues.<ref name = "Holmes_1987" /><ref name = "Singh_2020" /> The reactive center loop, which is crucial for its inhibitory function, protrudes from the central serpin domain and contains the Arg364-Met365 peptide bond that is specifically targeted and cleaved by plasmin.<ref name = "Holmes_1987" /<ref name = "Singh_2020" /> There are two main circulating forms: Met-α2AP, which has methionine at the N-terminus, and Asn-α2AP, which is N-terminally shortened and starts with asparagine; the latter form constitutes about 70% of plasma α2AP and is more efficiently cross-linked to fibrin.<ref name = "Lee_2004">Template:Cite journal</ref><ref name = "Singh_2020" /> The C-terminal region, rich in lysine residues, mediates the initial non-covalent binding to plasmin, facilitating the formation of a stable 1:1 stoichiometric complex.<ref name = "Singh_2020" /> This structural arrangement allows α2AP to efficiently interact with plasmin and be incorporated into fibrin clots via cross-linking by factor XIIIa.<ref name = "Singh_2020" /><ref name = "Baugh_2019">Template:Cite book</ref>

Function

Alpha 2-antiplasmin serves as the primary physiological inhibitor of plasmin, the key enzyme responsible for fibrin degradation during fibrinolysis.<ref name = "Lee_2004" /><ref name = "Baugh_2019" /> By rapidly forming a covalent complex with plasmin, α2AP prevents excessive breakdown of fibrin clots, thereby maintaining hemostatic balance.<ref name = "Lee_2004" /><ref name = "Baugh_2019" /><ref name = "RCD">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In addition to direct inhibition, α2AP interferes with the binding of plasminogen to fibrin, further regulating the initiation of fibrinolysis.<ref name = "Baugh_2019" /><ref name = "RCD" /> During clot formation, α2AP is cross-linked to fibrin by activated factor XIII, which increases the resistance of the clot to lysis and enhances clot stability.<ref name = "Baugh_2019" /><ref name = "RCD" /> This function is critical in preventing premature clot dissolution, but elevated levels of α2AP have been associated with increased risk of thrombotic events, such as stroke and myocardial infarction, due to impaired fibrinolysis.<ref name = "Hou_2008">Template:Cite journal</ref> Conversely, α2AP deficiency leads to increased susceptibility to bleeding because of uncontrolled plasmin activity and rapid clot breakdown.<ref name = "RCD" /> Thus, α2AP is essential for fine-tuning the balance between clot formation and dissolution, making it a potential therapeutic target in both thrombotic and bleeding disorders.<ref name = "Lee_2004" />

Clinical significance

Very few cases (<20) of alpha-2-antiplasmin deficiency have been described. As plasmin degrades blood clots, impaired inhibition of plasmin leads to a bleeding tendency, which was severe in the cases reported.

In liver cirrhosis, there is decreased production of alpha 2-antiplasmin, leading to decreased inactivation of plasmin and an increase in fibrinolysis. This is associated with an increased risk of bleeding in liver disease.<ref>Template:Cite book</ref> It has been suggested, however, that the observed decreases in alpha 2-antiplasmin levels are due to a chronic state of disseminated intravascular coagulation in cirrhosis rather than defective protein synthesis.<ref>Template:Cite journal</ref>

Interactions

Alpha 2-antiplasmin has been shown to interact with:

See also

References

Template:Reflist

Further reading

Template:Refbegin

Template:Refend

Template:Coagulation Template:Serpins Template:Alpha globulins

Retrieved from "https://wiki.sarg.dev/index.php?title=Alpha_2-antiplasmin&oldid=782926"