Deubiquitinating enzyme tethered to the mitochondrial outer membrane that acts as a key inhibitor of mitophagy by counteracting the action of parkin (PRKN): hydrolyzes ubiquitin attached by parkin on target proteins, such as RHOT1/MIRO1 and TOMM20, thereby blocking parkin's ability to drive mitophagy. Preferentially cleaves 'Lys-6'- and 'Lys-11'-linked polyubiquitin chains, 2 types of linkage that participate in mitophagic signaling. Does not cleave efficiently polyubiquitin phosphorylated at 'Ser-65' (By similarity). Acts as negative regulator of mitochondrial fusion by mediating deubiquitination of MFN1 and MFN2 (PubMed:24513856). 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). Inhibited by the diterpenoid derivative 15-oxospiramilactone (S3). Ubiquitinated by parkin (PRKN) at Lys-235 and Lys-289, leading to its degradation. Belongs to the peptidase C19 family. Extended N-terminus.