The blockage of the high-affinity lysine binding sites of plasminogen by EACA significantly inhibits prourokinase-induced plasminogen activation.
Prourokinase-induced plasminogen activation is complex and involves three distinct reactions: (1) plasminogen activation by the intrinsic activity of prourokinase; (2) prourokinase activation by plasmin; (3) plasminogen activation by urokinase. To further understand some of the mechanisms involved, the effects of epsilon-aminocaproic acid (EACA), a lysine analogue, on these reactions were studied. At a low range of concentrations (10-50 microM), EACA significantly inhibited prourokinase-induced (Glu-/Lys-) plasminogen activation, prourokinase activation by Lys-plasmin, and (Glu-/Lys-) plasminogen activation by urokinase. However, no inhibition of plasminogen activation by Ala158-prourokinase (a plasmin-resistant mutant) occurred. Therefore, the overall inhibition of EACA on prourokinase-induced plasminogen activation was mainly due to inhibition of reactions 2 and 3, by blocking the high-affinity lysine binding interaction between plasmin and prourokinase, as well as between plasminogen and urokinase. These findings were consistent with kinetic studies which suggested that binding of kringle 1-4 of plasmin to the N-terminal region of prourokinase significantly promotes prourokinase activation, and that binding of kringle 1-4 of plasminogen to the C-terminal lysine158 of urokinase significantly promotes plasminogen activation. In conclusion, EACA was found to inhibit, rather than promote, prourokinase-induced plasminogen activation due to its blocking of the high-affinity lysine binding sites on plasmin(ogen).
Sun
Ziyong
Z
Institute of Molecular Medicine, Nanjing University, 210093, Nanjing, PR China.
Chen
Yu-hong
YH
Wang
Ping
P
Zhang
Jing
J
Gurewich
Victor
V
Zhang
Peixiang
P
Liu
Jian-Ning
JN
D000614:Aminocaproates / Q000494:pharmacology*; D001665:Binding Sites; D004789:Enzyme Activation / Q000187:drug effects; D005341:Fibrinolysin / Q000494:pharmacology; D007700:Kinetics; D018082:Kringles; D008239:Lysine / Q000737:chemistry*; D008956:Models, Chemical; D010958:Plasminogen / Q000037:antagonists & inhibitors*; D010960:Plasminogen Activators / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors*; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors* / Q000737:chemistry
D000614:Aminocaproates; D011994:Recombinant Proteins; D010958:Plasminogen; D010960:Plasminogen Activators; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator; D008239:Lysine; C067551:saruplase