Peptidase C1A, cathepsin K (IPR015644)

Short name: Peptidase_C1A_cathepsin-K

Family relationships

  • Peptidase C1A (IPR013128)
    • Peptidase C1A, cathepsin K (IPR015644)


Cysteine peptidases have characteristic molecular topologies, which can be seen not only in their three-dimensional structures, but commonly also in the two-dimensional structures. These are peptidases in which the nucleophile is the sulphydryl group of a cysteine residue. Cysteine proteases are divided into clans (proteins which are evolutionary related), and further sub-divided into families, on the basis of the architecture of their catalytic dyad or triad [PMID: 11517925].

This group of cysteine peptidases belong to the MEROPS peptidase family C1, sub-family C1A (papain family, clan CA).

Cathepsin K is a cysteine protease expressed predominantly in osteoclasts. Activated cathepsin K cleaves key bone matrix proteins and is believed to play an important role in degrading the organic phase of bone during bone resorption. Cathepsin K is essential for normal bone resorption; Homo sapiens (Human) lacking cathepsin K exhibit pycnodysostosis, which is characterised by short stature and osteosclerosis [PMID: 14993931]. Histological and radiographic analysis of the cathepsin K-deficient Mus musculus (Mouse) revealed osteoporosis of the long bones and vertebrae, and abnormal joint morphology [PMID: 10491212].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0008234 cysteine-type peptidase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.