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Cytoplasmic organelle, composed of a cylindric core particle bound by two regulatory particles at each end, responsible for degrading endogenous proteins. Proteins to be destroyed are recognized by proteasomes because of the presence of ubiquitin conjugated to the targeted protein's lysine residue.
See also: ubiquitin-protease pathway.
[protease + -some ]
Farlex Partner Medical Dictionary © Farlex 2012


A cellular protein complex consisting of proteolytic enzymes that degrade endogenous proteins, especially those that are damaged, pathogenic, or no longer of use.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


, proteosome (prō′tē-ă-sōm″)
An enzymatic (protease) cell organelle that degrades misfolded or damaged proteins and modulates the quantity of regulatory proteins in the cell. The breakdown of proteins by proteasomes (proteolysis) is triggered when damaged proteins are tagged by ubiquitin.
Medical Dictionary, © 2009 Farlex and Partners


A large, cylindrical protein complex of several sub-units, present in the cytoplasm and nucleus of all cells and an essential component in cell metabolism. The function of the proteasome is to act as a kind of shredder, degrading unwanted proteins that have been tagged for destruction with UBIQUITIN chains. It strips proteins of their ubiquitin, unfolds them and catalyzed them to peptides. Proteasomes have aroused much interest as therapeutic trargets in cancer. The proteasome 26S is involved both in the induction and repression of APOPTOSIS. See also POLYUBIQUITINATION.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
The authors found that the initiation of substrate translocation is extensively coordinated with other regulatory events preparing the proteasome for processive substrate degradation.
Because the proteasome is a huge and complicated structure, proteasome assembly is regulated in a sophisticated manner.
Ixazomib (MLN2238) is a next-generation proteasome inhibitor that has replaced bortezomib in the clinic for multiple myeloma due to its improved activity and other characteristics, such as oral bioavailability [11, 12].
The decrease of proteasome activity upregulated the mRNA and protein level of IL-6 in the hRPE compared with that in control group without proteasome inhibition, but it reduces the secretion of MCP-1.
Subsequently, 10 [micro]L of samples was carried to reaction wells containing 30 [micro]L of an assay buffer (0.05% SDS in 100 mM Tris/HCl, pH = 7.5) and 10 [micro]L of the fluorogenic peptide AMC substrate, so that the total volume of the reaction mixture was 50 [micro]L and the concentration of SDS was 0.03% (the concentration needed for the maximal activation of the 20S proteasome).
When activated by signals, I[kappa]B is phosphorylated and ubiquitinated, which then leads them to be degraded by the proteasome [38, 39].
Triphase Accelerator is developing marizomib in both intravenous and oral formulations as a proteasome inhibitor for hematologic malignancies and solid tumors.
Conclusions: The upregulation of the proteasome activity observed upon quercetin or rutin treatment could be afforded by a mild increased of PARP-1.
Cilcane is a pentapeptide drug with an excellent safety profile and a novel mechanism of action compared to existing myeloma treatments, Research suggests the product will be synergistic in combination with a proteasome inhibitor, a class of drug normally given as a front line treatment for this disease and that this approach can also be extended to the treatment of other cancers, including breast cancer.
Proteasome inhibition reduces avian reovirus replication and apoptosis induction in cultured cells.
The PA28-dependent regulation of OPN expression was stimulated by high glucose and abrogated by synthetic peptides that block the binding of PA28 to 20S proteasomes. Therefore, the findings of this study provide novel insights into the role of the ubiquitin proteasome system (UPS) and specially the PA28 proteins, in regulating the microvascular injury in diabetes.
"These projects are in early stage of development, but build on Takeda's work with proteasome inhibitors, which has already led to new medicines for other diseases, including certain types of cancer," said Dr Timothy Wells, chief scientific officer at Medicines for Malaria Venture (MMV).

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