Streptokinase (SK) (SK)

Streptokinase is a 47-kDa non-enzymatic protein secreted by various strains of beta-hemolytic streptococci, most notably Streptococcus pyogenes [1, 3]. It serves as a potent thrombolytic agent by forming a high-affinity complex with human plasminogen, which subsequently activates other plasminogen molecules into plasmin [2, 4]. This cascade leads to the degradation of fibrin matrices within blood clots, making it a vital intervention for acute conditions such as myocardial infarction, pulmonary embolism, and deep vein thrombosis [1, 2]. Unlike tissue plasminogen activator (tPA), streptokinase is not fibrin-specific and can cause systemic fibrinolysis and a depletion of circulating fibrinogen [1]. Additionally, as a foreign bacterial protein, it is highly immunogenic, which can lead to allergic reactions or the development of neutralizing antibodies that typically preclude repeated administration within a short timeframe [1, 2]. Despite these challenges, streptokinase remains a widely used and cost-effective therapeutic option in many clinical settings globally [1].

Other names

Plasminogen activatorStreptococcal fibrinolysinSK

Streptokinase binds to human plasminogen to form a 1:1 stoichiometric complex. This complex undergoes a conformational change that exposes an active site, which then enzymatically converts free plasminogen molecules into active plasmin. Plasmin subsequently degrades fibrin, the primary structural component of blood clots [1, 2, 3].