Plasminogen (former name profibrinolysin) is an inactive precursor of plasmin. It is a plasma protein that is part of the fibrinolytic system. Plasmin is an important enzyme (EC 3.4.21.7) present in blood that degrades many blood plasma proteins, including fibrin clots. In circulation, plasminogen adopts a closed, activation-resistant conformation. Upon binding to clots, or to the cell surface, plasminogen adopts an open form that can be converted into active plasmin by a variety of enzymes, including tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), kallikrein, and factor XII (Hageman factor). Plasmin deficiency may lead to thrombosis, as the clots are not adequately degraded. Plasminogen deficiency in mice leads to defective liver repair, defective wound healing, reproductive abnormalities.