Ala bond in complement component C4 to form C4a and C4b, and Lys(or Arg)Lys bond in complement component C2 to form C2a and C2b: the "classical" pathway C3 convertase
Reaction: Cleavage of ArgAla bond in complement component C4 to form C4a and C4b, and Lys(or Arg)Lys bond in complement component C2 to form C2a and C2b: the "classical" pathway C3 convertase
Other names: C1 esterase; activated complement C1s; complement C
Comments: Activated from proenzyme C1s in plasma by complement subcomponent C . In peptidase family S1 (trypsin family)
Links to other databases: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, PDB, CAS registry number: 80295-70-1
References
1. Sim, R.B. The human complement system serine proteases C and C and their proenzymes. Methods Enzymol. 80 (1981) 26-42. [PMID: 6281620]
2. MacKinnon, C.M., Carter, P.E., Smyth, S.J., Dunbar, B. and Fothergill, J.E. Molecular cloning of cDNA for human complement component C1s. The complete amino acid sequence. Eur. J. Biochem. 169 (1987) 547-553 . [PMID: 3500856]
3. Müller-Eberhard, H.J. Molecular organization and function of the complement system. Annu. Rev. Biochem. 57 (1988) 321-347. [PMID: 3052276]
4. Skoog, M.T., Mehdi, S., Wiseman, J.S. and Bey, P. The specificity of two proteinases that cleave adjacent to arginine, C1 esterase and acrosin, for peptide p-nitroanilide substrates. Biochim. Biophys. Acta 996 (1989) 89-94. [PMID: 2500154]