EC - Cathepsin K

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IntEnz Enzyme Nomenclature


Accepted name:
cathepsin K
Other names:
cathepsin O [ambiguous]
cathepsin O2
cathepsin X [ambiguous]
Systematic name:



Prominently expressed in mammalian osteoclasts, and believed to play a role in bone resorption. In peptidase family C1 (papain family).

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , MEROPS , UniPathway
Protein domains and families: PROSITE:PDOC00126
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004216
CAS Registry Number: 94716-09-3
UniProtKB/Swiss-Prot: (10) [show] [UniProt]


  1. Inaoka, T., Bilbe, G., Ishibashi, O., Tezuka, K., Kumegawa, M. and Kokubo, T.
    Molecular cloning of human cDNA for cathepsin K: Novel cysteine proteinase predominantly expressed in bone.
    Biochem. Biophys. Res. Commun. 206: 89-96 (1995). [PMID: 7818555]
  2. Bossard, M.J., Tomaszek, T.A., Thompson, S.K., Amegadzie, B.Y., Hanning, C.R., Jones, C., Kurdyla, J.T., McNulty, D.E., Drake, F.H., Gowen, M. and Levy, M.A.
    Proteolytic activity of human osteoclast cathepsin K - Expression, purification, activation, and substrate identification.
    J. Biol. Chem. 271: 12517-12524 (1996). [PMID: 8647860]
  3. Bromme, D., Klaus, J.L., Okamoto, K., Rasnick, D. and Palmer, J.T.
    Peptidyl vinyl sulphones: A new class of potent and selective cysteine protease inhibitors - S2P2 specificity of human cathepsin O2 in comparison with cathepsins S and L.
    Biochem. J. 315: 85-89 (1996). [PMID: 8670136]
  4. Zhao, B.G., Janson, C.A., Amegadzie, B.Y., D'Alessio, K., Griffin, C., Hanning, C.R., Jones, C., Kurdyla, J., McQueney, M., Qiu, X.Y., Smith, W.W. and Abdel-Meguid, S.S.
    Crystal structure of human osteoclast cathepsin K complex with E-64.
    Nature Struct. Biol. 4: 109-111 (1997). [PMID: 9033588]
  5. McGrath, M.E., Klaus, J.L., Barnes, M.G. and Brömme, D.
    Crystal structure of human cathepsin K complexed with a potent inhibitor.
    Nature Struct. Biol. 4: 105-109 (1997). [PMID: 9033587]

[EC created 1997]