A cathepsin (Union of two Greek words, kata-:down and hepsein:boil) is a cysteine or aspartic protease, a type of protein that breaks apart other proteins, found in many types of cells including those in all animals. There are approximately a dozen members of this family, which are distinguished by their structure and which proteins they cleave. Most of the members become activated at the low pH found in lysosomes. Thus, the activity of this family lies almost entirely within those organelles.

Cathepsins have a vital role in mammalian cellular turnover, e.g. bone resorption. They degrade polypeptides and are distinguished by their substrate specificites.

Clinical significance

Cathepsins have been implicated in:
* Cancer [cite journal |author=Nomura T, Katunuma N |title=Involvement of cathepsins in the invasion, metastasis and proliferation of cancer cells |journal=J. Med. Invest. |volume=52 |issue=1-2 |pages=1–9 |year=2005 |month=February |pmid=15751268 |doi= |url= Review. ]
* Stroke [cite journal |author=Lipton P |title=Ischemic cell death in brain neurons |journal=Physiol. Rev. |volume=79 |issue=4 |pages=1431–568 |year=1999 |month=October |pmid=10508238 |doi= |url=]
* Alzheimer's disease,
* Arthritis [cite journal |author=Raptis SZ, Shapiro SD, Simmons PM, Cheng AM, Pham CT |title=Serine protease cathepsin G regulates adhesion-dependent neutrophil effector functions by modulating integrin clustering |journal=Immunity |volume=22 |issue=6 |pages=679–91 |year=2005 |month=June |pmid=15963783 |doi=10.1016/j.immuni.2005.03.015]
* Ebola, Cathepsin L and to a lesser extent cathepsin B have been found to be necessary for the virus to enter host cells.

Cathepsin A

Deficiencies in this protein are linked to multiple forms of galactosialidosis. The cathepsin A activity in lysates of metastatic lesions of malignant melanoma is significantly higher than in primary focus lysates. Cathepsin A increased in muscles moderately affected by muscular dystrophy and denervating diseases.

Cathepsin B

Cathepsin B seems to actually break down the proteins which cause amyloid plaque, the root of Alzheimer's symptoms, and may even be a pivotal part of the natural defense against this disease used by people who do not get it. Over expression of the encoded protein, which is a member of the peptidase C1 family, has been associated with esophageal adenocarcinoma and other tumors. Cathepsin B has also been implicated in the progression of various human tumors including ovarian cancer. Cathepsin B is also involved in apoptosis as well as degradation of myofibrillar proteins in myocardial infarction.

More details about the cathepsin protein is given in HuCAD Human Cathepsin Database.


The earliest record of "cathepsin" found in PubMed is from the Journal of Biological Chemistry in 1949. [cite journal |author=Maver ME, Greco AE |title=The hydrolysis of nucleoproteins by cathepsins from calf thymus |journal=J. Biol. Chem. |volume=181 |issue=2 |pages=853–60 |year=1949 |month=December |pmid=15393803 |doi= |url=]

However, references within this article indicate that they were first identified and named around the turn of the 20th century. Much of this earlier work was done in the laboratory of Max Bergmann, who spent the first several decades of the century defining these proteases. [cite journal |author=Bergmann M, Fruton JS |title=REGARDING THE GENERAL NATURE OF CATHEPTIC ENZYMES |journal=Science (journal) |volume=84 |issue=2169 |pages=89–90 |year=1936 |month=July |pmid=17748131 |doi=10.1126/science.84.2169.89 |url=]


External links

* [ HuCAD]

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