F9

Factor IX, also known as F9, is a vitamin K-dependent coagulation protein encoded by the F9 gene and produced in the liver. Initially circulating as an inactive zymogen, F9 is converted to its active form through the removal of an activating peptide by factor XIa. This results in the formation of active heavy and light chains linked by disulfide bonds. F9's mechanism of action involves interactions with Ca+2 ions, membrane phospholipids, and factor VIII within the coagulation cascade, leading to the activation of factor X and participation in blood coagulation. F9 is crucial for normal blood clotting, and mutations in the F9 gene can result in hemophilia B or Christmas disease, a recessive X-linked condition caused by a deficiency of factor IX.