Although included in lists of deubiquitinases in several publications, ec, PAN2 and Usp39 lack key catalytic residues and are classed as non-peptidase homologs of the C19 family in MEROPS (http://merops.sanger.ac.uk/). Moreover, all isoforms of ec and the human ortholog of Usp39 have been shown experimentally to lack deubiquitinase activity (FBrf0200872 and PMID:18728397, respectively). Thus, all three genes are omitted from this gene group and are instead listed in the 'C19 NON-PEPTIDASE HOMOLOGS' gene group.