Component of the lid subcomplex of the 26S proteasome, a multiprotein complex involved in the ATP-dependent degradation of ubiquitinated proteins. RPN11 is the only catalytically active member of the lid and serves as the essential deubiquitinase of the proteasome. Thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin (a 76-residue protein attached to proteins as an intracellular targeting signal). Component of the lid subcomplex of the 19S proteasome regulatory particle complex (also named PA700 complex). The 26S proteasome consists of a 20S proteasome core and two 19S regulatory subunits. Interacts directly with RPN8 and STS1. The JAMM motif is required for the deubiquitination and degradation of ubiquitinated substrates. N-acetylated by NAT3. Present with 16400 molecules/cell in log phase SD medium. Belongs to the peptidase M67A family.