Secrete streptokinase in order to accelerate the conversion of human plasminogen to plasmin (12). Lacking enzymatic activity itself, streptokinase evolves its function by forming a stoichiometric 1:1 complex with plasminogen or a trimolecular complex with plasminogen and fibrinogen. The activator complexes can bind at the bacterial surface via host factor receptors and convert other plasminogen mo
N activator streptokinase might contribute to contact system activation by S. pyogenes. Here, we report that the human contact system is activated by the action of streptokinase. The role of secreted and surfacebound streptokinase in this process was investigated by comparing an M49 S. pyogenes wild-type strain with its isogenic ska mutant, which is unable to trigger plasmin activity in human plas