Factor IX

More reference expression dataBioGPSEnsemblUniProtRefSeq (mRNA)RefSeq (protein)Location (UCSC)Chr X: 139.53 – 139.56 MbChr X: 59.04 – 59.08 MbPubMed searchWikidata

Factor IX (EC3.4.21.22) is one of the serine proteases involved in coagulation; it belongs to peptidase family S1. Deficiency of this protein causes haemophilia B.

It was discovered in 1952 after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to haemophilia. Coagulation factor IX is on the World Health Organization's List of Essential Medicines.