cathepsin-K (cathepsin O, cathepsin X, cathepsin O2, CTSK, CTSO CTSO2)

Function

• lysosomal protein involved in osteoclastic bone resorption
• may participate partially in bone remodeling
• potent endoprotease activity against fibrinogen at acid pH
• role in extracellular matrix degradation (putative)
• broad proteolytic activity
• with small-molecule substrates & inhibitors, the major determinant of specificity is P2, which is preferably Leu, Met > Phe, & not Arg

Structure

belongs to the peptidase C1 family

Compartment

Lysosome

Expression

predominantly expressed in osteclasts (bones)

Pathology

• defects in CTSK are associated with pycnodysostosis

Laboratory

• CTSK gene mutation
• cathepsin K in serum/plasma

More general terms

• cathepsin

Database

• UniProt: http://www.uniprot.org/uniprot/P43235.html
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:1513
• OMIM: https://mirror.omim.org/entry/265800
• OMIM: https://mirror.omim.org/entry/601105
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=1513