The inhibition of TNK-t-PA by C1-inhibitor.
TNK-t-PA is a recombinant mutant of tissue plasminogen activator that has a longer half-life and higher selectivity for fibrin than normal tissue plasminogen activator (t-PA). In addition, it is reported to be serpin resistant because of reduced inhibition by plasminogen activator inhibitor-1. In this study, we have investigated the inhibition of TNK-t-PA by the serpin C1-inhibitor. TNK-t-PA is inhibited with a second-order rate constant of 7.5 per mol/l per s compared with 4.5 per mol/l per s for t-PA. In both cases, the stoichiometry was close to 20, indicating that C1-inhibitor was predominantly a substrate for both forms of t-PA. The formation of cleaved C1-inhibitor was seen on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the t-PA-C1-inhibitor (or TNK-t-PA-C1-inhibitor) complex seen on SDS-PAGE and by zymography. Although the rates of inhibition are very slow in vitro, the fact that in vivo formation of the t-PA-C1-inhibitor complex after infusion of t-PA has been well documented suggests that TNK-t-PA will also be inhibited by C1-inhibitor in vivo and, perhaps more importantly, could cause a significant reduction in C1-inhibitor concentration.
Department of Oral Medicine and Diagnostic Sciences, University of Illinois at Chicago, 60612, USA.
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Patston
D003174:Complement C1 Inactivator Proteins / Q000378:metabolism / Q000494:pharmacology*; D050718:Complement C1 Inhibitor Protein; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007700:Kinetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D010959:Tissue Plasminogen Activator / Q000037:antagonists & inhibitors* / Q000378:metabolism
D003174:Complement C1 Inactivator Proteins; D050718:Complement C1 Inhibitor Protein; D015853:Cysteine Proteinase Inhibitors; D011994:Recombinant Proteins; C104096:TNK-tissue plasminogen activator; D010959:Tissue Plasminogen Activator