Streptokinase-producing streptococci grown in human plasma acquire unregulated cell-associated plasmin activity.

Group A streptococci grown in the presence of human plasma generated plasmin from plasminogen and captured the functional enzyme to a specific cell-surface receptor. Bacteria-bound plasmin was not regulated by alpha 2-antiplasmin present in the medium. The ability of the bacteria to acquire cell-associated plasmin activity was dependent on both the presence of plasminogen in the culture medium and the production of a bacterial plasminogen activator, streptokinase. The ability of group A streptococci to produce a plasminogen activator and capture resulting plasmin in an unregulatable form could provide the organism with a mechanism for invasion of normal tissue barriers.