IUBMB Enzyme Nomenclature


Accepted name: calicivirin

Reaction: Endopeptidase with a preference for cleavage when the P1 position is occupied by Glu and the P1' position is occupied by Gly

Other name(s): Camberwell virus processing peptidase; Chiba virus processing peptidase; Norwalk virus processing peptidase; Southampton virus processing peptidase; Southampton virus; norovirus virus processing peptidase; calicivirus trypsin-like cysteine protease; calicivirus TCP; calicivirus 3C-like protease; calicivirus endopeptidase; rabbit hemorrhagic disease virus 3C endopeptidase

Comments: Viruses that are members of the Norovirus genus (Caliciviridae family) are a major cause of epidemic acute viral gastroenteritis [4]. The nonstructural proteins of these viruses are produced by proteolytic cleavage of a large precursor polyprotein, performed by a protease that is incorporated into the polyprotein [6]. Cleavage sites are apparently defined by features based on both sequence and structure since several sites in the polyprotein fulfilling the identified sequence requirements are not cleaved [1]. The presence of acidic (Asp), basic (Arg), aromatic (Tyr) or aliphatic (Leu) amino acids at the P1′ position results in only minor differences in cleavage efficiency, suggesting that steric or conformational constraints may play a role in determining specificity [1]. Changes to the amino acid at the P2 position do not alter cleavage efficiency [1,2]. Belongs in peptidase family C37.

Links to other databases: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, PDB, CAS registry number:


1. Meyers, G., Rossi, C. and Thiel, H.J. Calicivirus endopeptidases. In: Barrett, A.J., Rawlings, N.D. and Woessner, J.F. (Eds), Handbook of Proteolytic Enzymes, 2nd edn, Elsevier, London, 2004, pp. 1380-1382.

2. Wirblich, C., Sibilia, M., Boniotti, M.B., Rossi, C., Thiel, H.J. and Meyers, G. 3C-like protease of rabbit hemorrhagic disease virus: identification of cleavage sites in the ORF1 polyprotein and analysis of cleavage specificity. J. Virol. 69 (1995) 7159-7168. [PMID: 7474137]

3. Martín Alonso, J.M., Casais, R., Boga, J.A. and Parra, F. Processing of rabbit hemorrhagic disease virus polyprotein. J. Virol. 70 (1996) 1261-1265. [PMID: 8551592]

4. Liu, B., Clarke, I.N. and Lambden, P.R. Polyprotein processing in Southampton virus: identification of 3C-like protease cleavage sites by in vitro mutagenesis. J. Virol. 70 (1996) 2605-2610. [PMID: 8642693]

5. Liu, B.L., Viljoen, G.J., Clarke, I.N. and Lambden, P.R. Identification of further proteolytic cleavage sites in the Southampton calicivirus polyprotein by expression of the viral protease in E. coli. J. Gen. Virol. 80 (1999) 291-296. [PMID: 10073687]

[EC created 2007]

Return to EC 3.4.22 home page
Return to EC 3.4 home page
Return to EC 3 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page