Deubiquitinating enzyme that cleaves both 'Lys-48'-linked and 'Lys-63'-linked poly-ubiquitin chains (in vitro). 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).