Human blood contains the enzyme plasmin. The plasmin enzyme exists in the blood in the form of plasminogen. Plasminogen is inactive. TPA converts inactive plasminogen to active plasminogen. Activated plasminogen dissolves blood clots in the human body. The process of dissolving clotted blood is called fibrinolysis. Protects people from heart attack or stroke. Heals the patient by dissolving the blood block. In 1970, the enzyme streptokinase was isolated from bacteria, which dissolves clotted blood.