Deubiquitinating enzyme that plays a role in behavior, possibly by regulating GABA action. May act by mediating the deubiquitination of GAD1/GAD67 (By similarity). Has almost no deubiquitinating activity by itself and requires the interaction with WDR48 to have a high activity. Not involved in deubiquitination of monoubiquitinated FANCD2 (By similarity). 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). Interacts with WDR48. Interacts with WDR20. Belongs to the peptidase C19 family. USP12/USP46 subfamily.