EC 3.4.21.6

Reaction: Selective cleavage of ArgThr and then ArgIle bonds in prothrombin to form thrombin

Other name(s): thrombokinase; prothrombase; prothrombinase; activated blood-coagulation factor X; autoprothrombin C; thromboplastin; plasma thromboplastin; factor Xa; activated Stuart-Prower factor; activated factor X

Comments: A blood coagulation factor formed from the proenzyme factor X by limited proteolysis. Factor X is a glycoprotein composed of a heavy chain and a light chain, which are generated from a precursor protein by the excision of the tripeptide RKR and held together by one or more disulfide bonds. The activated factor Xa converts prothrombin to thrombin in the presence of factor Va, Ca²⁺ and phospholipids. Scutelarin (EC 3.4.21.60) has similar specificity, but does not require factor Va.

Links to other databases: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, PDB, CAS registry number: 9002-05-5

References:

1. Fujikawa, K. and Davie, E.W. Bovine factor X (Stuart factor). Methods Enzymol. 45 (1976) 89-95. [PMID: 1012041]

2. Jesty, J. and Nemerson, Y. The activation of bovine coagulation factor X. Methods Enzymol. 45 (1976) 95-107. [PMID: 1012042]

3. 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]

4. Jackson, C.M. and Nemerson, Y. Blood coagulation. Annu. Rev. Biochem. 49 (1980) 765-811. [PMID: 6996572]

5. McMullen, B.A., Fujikawa, K., Kisiel, W., Sasagawa, T., Howald, W.N., Kwa, E.Y. and Weinstein, B. Complete amino acid sequence of the light chain of human blood coagulation factor X: evidence for identification of residue 63 as β-hydroxyaspartic acid. Biochemistry 22 (1983) 2875-2884. [PMID: 6871167]

6. 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]