IUBMB Enzyme Nomenclature


Accepted name: cathepsin K

Reaction: Broad proteolytic activity. With small-molecule substrates and inhibitors, the major determinant of specificity is P2, which is preferably Leu, Met > Phe, and not Arg

Other names: cathepsin O and cathepsin X (both misleading, having been used for other enzymes); cathepsin O2

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

Links to other databases: BRENDA, EXPASY, KEGG, MEROPS, Metacyc, PDB, CAS registry number: 94716-09-3


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 (1995) 89-96. [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 (1996) 12517-12524. [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 (1996) 85-89. [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 (1997) 109-111. [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 (1997) 105-109. [PMID: 9033587]

[EC created 1997]

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