Summary
The kinetics of the activation of plasminogen into plasmin with urokinase and the
inactivation rate of the plasmin formed are studied.
As a first order reaction is obtained with low plasminogen concentrations and a zero-order
reaction is obtained with high concentrations, the activation seems to follow the
Michaelis-Menten’s law. The reaction does not go to completion, however. Different
activity levels, which are dependent on the urokinase concentration, can be observed.
The activation rate increases with temperature. A maximum can be seen at about 42°
C.
Between 4° C and 15° C, the inactivation of the plasmin formed is minimal, but it
increases rapidly at higher temperatures. The inactivation follows approximately a
first order reaction with respect to time. If the plasminogen concentration is low,
the over-all reaction will be that of two consecutive first order reactions.
