Abstract
Steady state kinetics of activation of human and bovine plasminogens by streptokinase and its equimolar complexes with various activated forms of human plasminogen.
Highlights
The steady state kinetic parameters of activation of human Glu- and Lys-plasminogens and bovine plasminogen by streptokinase and its equimolar complexes with Gluand Lys-plasminogen, Lys-plasmin, and the plasmin-derived light(B) chain, as well as urokinase, were determined
The formation of the active light(B) chain. streptokinase complex is much slower than the formation of the active plasmin. or plasminogen. streptokinase complexes, since at similar concentrations of 1 to 5 x 10m7M it takes between 5 to 7 min to develop maximum esterase activity, whereas the plasmin. streptokinase complex has maximum esterase activity on mixing, and the Lys-plasminogen . streptokinase complex has maximum esterase activity in 1 min
In a previous report [15] it was shown that the human plasmin-derived light(B) chain forms a stoichiometric complex with streptokinase, and in this study (Fig. 1) it was demonstrated that both esterase and activator activities increase linearly to a level which corresponds to the stoichiometric complex
Summary
The steady state kinetic parameters of activation of human Glu- and Lys-plasminogens and bovine plasminogen by streptokinase and its equimolar complexes with Gluand Lys-plasminogen, Lys-plasmin, and the plasmin-derived light(B) chain, as well as urokinase, were determined. The dissociation constant, K,,,, for activation of human plasminogen, by all the activators studied was comparable (about 1 to 3 PM). Glu-plasminogen activation by streptokinase (Glu-plasminogen streptokinase) and the light(B) chain.streptokinase complex proceeded at one-third the rate of that of Lys-plasminogen activation, with a k,,, for Glu-plasminogen of about 7 and 19 s-l compared to a k,,, for Lys-plasminogen of about 27 and 52 s’, respectively. 6.0 and 30” at concentrations of 3 x 10m9 M, indicating a very low dissociation constant and probably an even lower one for streptokinase binding to both plasminogen and plasmin.
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