Deubiquitinating enzyme that removes conjugated ubiquitin from specific proteins to regulate different cellular processes that may include cell proliferation, progression through the cell cycle, apoptosis, cell migration, and the cellular response to viral infection. 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). Detected in T-cell, myeloid, and embryonic stem cell lines. Belongs to the peptidase C19 family. USP17 subfamily.