EC - Coagulation factor IXa

  IntEnz view ENZYME view

IntEnz Enzyme Nomenclature


Accepted name:
coagulation factor IXa
Other names:
activated Christmas factor
activated blood coagulation factor XI
activated blood-coagulation factor IX
autoprothrombin II
blood platelet cofactor II
blood-coagulation factor IXa
Systematic name:



A chymotrypsin homologue, and one of the γ-carboxyglutamic acid-containing blood coagulation factors. The proenzyme factor IX is activated by factor XIa. In peptidase family S1 (trypsin family).

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , MEROPS , UniPathway
Protein domains and families: PROSITE:PDOC00124
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004252
CAS Registry Number: 37316-87-3
UniProtKB/Swiss-Prot: (13) [show] [UniProt]


  1. Fujikawa, K. and Davie, E.W.
    Bovine factor IX (Christmas factor).
    Methods Enzymol. 45 : 74-83 (1976). [PMID: 1012029]
  2. Davie, E.W., Fujikawa, K., Kurachi, K. and Kisiel, W.
    The role of serine proteases in the blood coagulation cascade.
    Adv. Enzymol. 48 : 277-318 (1979). [PMID: 367103]
  3. Link, R.P. and Castellino, F.J.
    Kinetic comparison of bovine blood coagulation factors IXaα and IXaβ towards bovine factor X.
    Biochemistry 22 : 4033-4041 (1983). [PMID: 6412750]
  4. Cho, K., Tanaka, T., Cook, R.R., Kisiel, W., Fujikawa, K., Kurachi, K. and Powers, J.C.
    Active-site mapping of bovine and human blood coagulation serine proteases using synthetic peptide 4-nitroanilide and thio ester substrates.
    Biochemistry 23 : 644-650 (1984). [PMID: 6370301]

[EC created 1978]