System engineering analysis of fibrinolysis by plasmin: transient behaviors and linear properties

System analysis was applied to the fibrinolysis system by plasmin. The behaviors of plasminogen activating factor, activating enzyme, plasmin, plasminogen, plasmin substrate, reacted products and intermediate products are expressed by rate equations. The temporal changes in the concentrations of components in the system are consistent to physiological observation. Because plasminogen and plasmin substrate exist in sufficient amount, the system is reduced to a linear one. Fibrinolysis system is unstable and insensitive to changes in rate constants while it is controllable. The most critical process is producing the activating enzyme and the free plasmin. The optimized feedback control converged the impulse responses of free plasmin and reacted product. Present study is available to evaluate functional and quantitative aspects of the system.