Deubiquitinating enzyme that acts as a key inhibitor of mitophagy by counteracting the action of parkin (park). 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). RNAi-mediated knockdown rescues the defective mitophagy caused by mutations in parkin and improves mitochondrial integrity in park- or PINK1-deficient flies. Moreover, knockdown in dopaminergic neurons protects flies against paraquat herbicide toxicity in vivo, ameliorating defects in dopamine levels, motor function and organismal survival. Belongs to the peptidase C19 family.