Kinetic analysis of plasminogen activation by staphylokinase/plasminogen complex in the presence of fibrin.

Staphylokinase (SAK) expresses plasminogen activator activity by forming a complex with plasminogen. In order to elucidate the mechanism for the expression of enzymatic activity of the complex, a cross-linked staphylokinase/plasminogen (SAK/plg) complex was produced with disuccinimidyl suberate, and its enzymatic characteristics were compared with those of a streptokinase/plasminogen (SK/plg) complex. SAK/plg complex and SK/plg complex showed a band with a molecular weight of 110 kDa and 140 kDa by SDS-PAGE under non-reduced condition, respectively. Both complexes exhibited plasminogen activator activity in a concentration-dependent manner on fibrin film and synthetic chromogenic substrate assay. The kinetic analysis of enzymatic activity of both complexes was performed. The plasminogen activator activity of SAK/plg complex was enhanced about 5-fold in the presence of FCB-2. However, SK/plg complex showed only 1.7-fold increase in the presence of FCB-2. These findings indicate that the SAK/plg complex reacts with fibrin, and efficient plasminogen activation is induced on fibrin surface.