Streptokinase as Fibrinolytic Agent

Abstract

Accumulation of fibrin in the blood vessels usually results in the thrombosis, leading to myocardial infarction and other cardiovascular diseases. For thrombolytic therapy microbial fibrinolytic enzymes have now attracted much more attention than typical thrombolytic agents because of the high cost and undesirable side effect. In this study one of the most important fibrinolytic agents streptokinase was selected. The b-hemolytic streptococci isolated from different samples of blood and biomass from infected throat of tonsilitis patients, 50 isolates exhibited streptokinase activity. S-8, identified a new variant of Streptococcus equisimilis was found to be excellent streptokinase producer in liquid state fermentation biotechnology. This indigenously produced streptokinase showed 1200 U mL^-1 activity, 415 U mg^-1 specific activity, with 16.6 fold purification. The purified streptokinase has molecular mass 47 KDa and its apparent K_m and V_max values for fibrinlysis were 1.8 μmol and 5370 IU/mL, respectively. The optimum temperature and pH for catalytic activity were 37 ºC and 7.4. The activation energy requirement for the formation of ES complex was 30.2 KJ/mol. Enthalpy (DH*), entropy (DS*) and Gibb’s free energy demand for streptokinase inactivation were 27.3, -91.6 and -22.8 KJ mol^-1. Gibb’s free energy (DG*) demand for substrate binding and transition state stabilization were also determined.