The Full form of TPA is Tissue Plasminogen Activator. TPA is an enzyme that helps in dissolving clots. TPA is made by the cells lining blood vessels and has also been made in the laboratory. It is systemic thrombolytic (clot-busting) agent and is used in the treatment of stroke and heart attack. Activase (alteplase) is a Tissue Plasminogen Activator produced by recombinant DNA technology. Recombinant TPA is abbreviated R-TPA. The central enzyme component in this system is the glycoprotein plasminogen present in most extravascular fluids and plasma. Plasminogen is a zymogen of a serine protease which, following partial cleavage by a plasminogen activator, is converted into its active form plasmin. Plasmin is involved in a variety of biological processes, including growth, cell migration, inflammation and tumour invasion, although its primary function is assumed to be lysis of fibrin in the vasculature. Two plasminogen activators have been found in the human body, the tissue-type plasminogen activator (t-PA) and the urinary-type activator (u-PA). T-PA is the principle activator of plasminogen in blood, whereas u-PA has its major function in tissue-related proteolysis and is believed to only be secondary to t-PA in the removal of intravascular fibrin.