Alpha 2-antiplasmin and alpha 2-macroglobulin inactivate plasmin. It functions as an inhibitor of fibrinolysis by inhibiting plasmin and kallikrein. These include thrombin, tissue activating plasminogen and plasmin. It inhibits proteases like chymotrypsin, kallikrein, plasmin, thrombin, and trypsin. Alteplase is a serine protease that assists fibrin in the conversion of plasminogen to plasmin. It works by converting plasminogen to plasmin in a blood clot. Its action on plasmin independently slows fibrinolysis. Such enzymes include proteolytic enzymes like plasmin, the enzyme responsible for fibrinolysis. This hypothesis is supported by lytic effects in vitro by plasmin. Activation is achieved through an interacting protease cascade involving plasmin and stromelysin 1 (MMP-3). Fibrinolysis is the physiological breakdown of blood clots by enzymes such as plasmin. Urokinase cleaves the zymogen plasminogen into serine protease plasmin. The main enzyme responsible for this process (plasmin) is regulated by various activators and inhibitors. This drug is made by transgenic bacteria and converts plasminogen into the clot-dissolving enzyme, plasmin. The excess plasmin also activates the complement and kinin systems.