Plasmin and Plasminogen |
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| Plasmin
is an important enzyme
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.
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).
Plasminogen 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. |
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