Tissue plasminogen activator (tPA, PLAT) is a protein involved in the breakdown of blood clots. It is a serine protease (EC 3.4.21.68) found on endothelial cells, the cells that line the blood vessels. As an enzyme, it catalyzes the conversion of plasminogen to plasmin, the major enzyme responsible for clot breakdown. Because it works on the clotting system, tPA is used in clinical medicine to treat embolic orthrombotic stroke. Use is contraindicated in hemorrhagic stroke and head trauma. The antidote for tPA in case of toxicity is aminocaproic acid.
tPA may be manufactured using recombinant biotechnology techniques. tPA created this way may be referred to as recombinant tissue plasminogen activator (rtPA).