[Proteasomes. Complex proteases lead to a new understanding of cellular regulation through proteolysis]

Proteasomes are large multicatalytic protease complexes which fulfill central functions in major proteolytic pathways of the eukaryotic cell. Two types of proteasomes are known: the cylindrically shaped 20S proteasome (700 kDa) and the 26S proteasome (1700 kDa) which contains the 20S proteasome as a functional core. Proteasomes are needed for stress-dependent and ubiquitin-mediated proteolysis. They are involved in degradation of abnormal, short-lived, and regulatory proteins. Proteasomes are important for cell differentiation and adaptation to environmental changes. Proteasomes have been shown to function in the control of the cell cycle and are suggested to be involved in antigen presentation by processing of intracellular proteins to antigenic peptides.