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 (PubMed:19075014, PubMed:26388029). Not involved in deubiquitination of monoubiquitinated FANCD2 (PubMed:19075014).