Peroxynitrite and fibrinolytic system: The effect of peroxynitrite on plasmin activity

We have shown that peroxynitrite (ONOO-) inhibits streptokinase-induced conversion of plasminogen to plasmin in a concentration-dependent manner and reduces both amidolytic (IC(50)similar to280 muM at 10 muM concentration of enzyme) and proteolytic activity of plasmin. Spectrophotometric and immunoblot analysis of peroxynitrite-treated plasminogen demonstrates a concentration-dependent increase in its nitrotyrosine residues that correlates with a decreased generation of active plasmin. Peroxynitrite (1 mM) causes the nitration of 2.9 tyrosines per plasminogen molecule. Glutathione, like deferoxamine, partially protects plasminogen from peroxynitrite-induced inactivation and reduces the extent of tyrosine nitration. These data suggest that nitration of plasminogen tyrosine residues by peroxynitrite might play an important role in the inhibition of plasmin catalytic activity.