IUBMB Enzyme Nomenclature


Accepted name: coagulation factor IXa

Reaction: Selective cleavage of ArgIle bond in factor X to form factor Xa

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

Comments: 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: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, PDB, CAS registry number: 37316-87-3


1. Fujikawa, K. and Davie, E.W. Bovine factor IX (Christmas factor). Methods Enzymol. 45 (1976) 74-83. [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 (1979) 277-318. [PMID: 367103]

3. Link, R.P. and Castellino, F.J. Kinetic comparison of bovine blood coagulation factor IXaα and IXaβ towards bovine factor X. Biochemistry 22 (1983) 4033-4041. [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 (1984) 644-650. [PMID: 6370301]

[EC created 1978]

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