Source:http://linkedlifedata.com/resource/umls/id/C0286330
NCI: Proteasomes are large multicatalytic proteolytic complexes found in all eukaryotic cells, and simpler forms have been found in archaebacteria and certain eubacteria. In eukaryotes, the 20S proteasome also exists as the central core of the 26S (2000 kDa) proteasome complex, which catalyzes the degradation of ubiquitin-conjugated proteins and contains an additional 19S complex, composed of regulatory proteins and six ATPases.