EC - Proteasome endopeptidase complex

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IntEnz Enzyme Nomenclature


Accepted name:
proteasome endopeptidase complex
Other names:
26S protease
alkaline protease
large multicatalytic protease
multicatalytic endopeptidase complex
multicatalytic proteinase
multicatalytic proteinase (complex)
proteasome organelle
tricorn protease
tricorn proteinase
Systematic name:



A 20-S protein composed of 28 subunits arranged in four rings of seven. The outer rings are composed of a subunits, but the b subunits forming the inner rings are responsible for peptidase activity. In eukaryotic organisms there are up to seven different types of b subunits, three of which may carry the N-terminal threonine residues that are the nucleophiles in catalysis, and show different specificities. The molecule is barrel-shaped, and the active sites are on the inner surfaces. Terminal apertures restrict access of substrates to the active sites. There is evidence that catalytic subunits are replaced by others under some conditions so as to alter the specificity of proteolysis, perhaps optimizing it for the formation of antigenic peptides. A complex of the 20-S proteasome endopeptidase complex with a 19-S regulatory unit is the 26-S proteasome that degrades ubiquitin-protein conjugates. Type example of peptidase family T1. Formerly EC, EC and EC

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , MEROPS , UniPathway
Protein domains and families: PROSITE:PDOC00326 , PROSITE:PDOC00668
Structural data: CSA , EC2PDB
CAS Registry Number: 140879-24-9
UniProtKB/Swiss-Prot: (247) [show] [UniProt]


  1. Seemüller, E., Lupas, A., Stock, D., Löwe, J., Huber, R. and Baumeister, W.
    Proteasome from Thermoplasma acidophilum: a threonine protease.
    Science 268 : 579-582 (1995). [PMID: 7725107]
  2. Coux, O., Tanaka, K. and Goldberg, A.L.
    Structure and functions of the 20S and 26S proteasomes.
    Annu. Rev. Biochem. 65 : 801-847 (1996). [PMID: 8811196]
  3. Groll, M., Ditzel, L., Löwe, J., Stock, D., Bochtler, M., Bartunik, H.D. and Huber, R.
    Structure of 20S proteasome from yeast at 2.4Å resolution.
    Nature 386 : 463-471 (1997). [PMID: 9087403]
  4. Dick, T.P., Nussbaum, A.K., Deeg, M., Heinemeyer, W., Groll, M., Schirle, M., Keilholz, W., Stevanovic, S., Wolf, D.H., Huber, R., Rammensee, H.G. and Schild, H.
    Contribution of proteasomal β-subunits to the cleavage of peptide substrates analyzed with yeast mutants.
    J. Biol. Chem. 386 : 25637-25646 (1998). [PMID: 9748229]

[EC created 1978 as EC, part transferred 1989 to EC, transferred 1992 to EC, transferred 2000 to EC]