Factor IX also known as Factor9, F9 plays a crucial role in the blood coagulation cascade, which is essential for hemostasis following tissue injury. This vitamin K-dependent serine protease is synthesized in the liver and circulates as an inactive precursor until activated by factor XIa-mediated proteolytic cleavage, resulting in factor IXa. The active form consists of a 145 amino acid light chain and a 236 amino acid catalytic heavy chain, which are linked by disulfide bonds, highlighting the importance of structural integrity for function. Disruptions in the Factor IX gene, such as point mutations or deletions, can lead to hemophilia B, a serious bleeding disorder that underscores the significance of Factor IX in maintaining normal blood clotting.