Immunoproteasome 20S (human), (purified)

The eukaryotic proteasome contains 7α-type and 7 β-type subunits. Upon stimulation with IFN-γ, the three active β subunits, β1 (Y), β2 (Z) and β5 (X) are exchanged to their immunocounterparts, namely β1i (LMP-2), β2i (MECL-1) and β5i (LMP-7). This results in a change in proteasomal substrate specificity. Some groups have reported increases in chymotrypsin-like and trypsin-like activities while others have reported no changes or even decreased activities after such treatment.