Proteins containing a catalytic domain (serine protease) that includes the three principal amino acids participating in catalysis: serine, histidine, and aspartic acid. These proteins circulate as inert zymogens, upon activation selectively hydrolyze bonds containing arginine or lysine, and are regulated by inhibitors termed serpins. Serine proteases involved in hemostasis include coagulation factors FII, FVII, FIX, FX, FXI, FXII, and Prekallikrein, as well as the fibrinolytic pathway proteins Plasminogen and tissue Plasminogen Activator (t-PA).
