IUBMB Enzyme Nomenclature


Accepted name: equine arterivirus serine peptidase

Reaction: Cleavage of (Glu/Gln)(Gly/Ser/Ala) in arterivirus replicase translation products ORF1a and ORF1ab

Glossary: arterivirus nsp4; equine arteritis virus serine peptidase; 3C-like serine protease; 3C-like Ser protease; 3CLSP; nonstructural protein 4 serine protease, Nsp4 serine protease; nsp4 serine protease; Nsp4 SP; chymotrypsin-like serine proteinase nsp4

Comments: In the equine arterivirus (EAV), the replicase gene is translated into open reading frame 1a (ORF1a) and ORF1ab polyproteins. This enzyme is the main viral proteinase and processes five cleavage sites in the ORF1a protein and three in the ORF1b-encoded part of the ORF1ab protein to yield nonstructural proteins (nsp5-nsp12) [3]. It combines the catalytic system of a chymotrypsin-like serine peptidase (His-Asp-Ser catalytic triad) with the substrate specificity of a 3C-like serine peptidase (Glu or Gln) at the P1 position and a small amino-acid residue (Gly, Ser or Ala) at the P1' position [1]. Cleavage of ORF1ab by this enzyme is essential for viral replication [2]. Belongs in peptidase family S32.

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


1. Snijder, E.J., Wassenaar, A.L., van Dinten, L.C., Spaan, W.J. and Gorbalenya, A.E. The arterivirus nsp4 protease is the prototype of a novel group of chymotrypsin-like enzymes, the 3C-like serine proteases. J. Biol. Chem. 271 (1996) 4864-4871. [PMID: 8617757]

2. van Dinten, L.C., Rensen, S., Gorbalenya, A.E. and Snijder, E.J. Proteolytic processing of the open reading frame 1b-encoded part of arterivirus replicase is mediated by nsp4 serine protease and is essential for virus replication. J. Virol. 73 (1999) 2027-2037. [PMID: 9971783]

3. Barrette-Ng, I.H., Ng, K.K., Mark, B.L., Van Aken, D., Cherney, M.M., Garen, C., Kolodenko, Y., Gorbalenya, A.E., Snijder, E.J. and James, M.N. Structure of arterivirus nsp4. The smallest chymotrypsin-like proteinase with an α/β C-terminal extension and alternate conformations of the oxyanion hole. J. Biol. Chem. 277 (2002) 39960-39966. [PMID: 12163505]

[EC created 2006]

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