Ubiquitin-protein hydrolase which cleaves ubiquitin from ubiquitinated proteins (PubMed:12006614, PubMed:11683918). Plays a role in embryo osmoregulation (PubMed:12006614). Probably by regulating osmosis, controls actin redistribution in the 1-cell embryos and thus actin-dependent processes such as cytokinesis and P-granules segregation (PubMed:12006614, PubMed:11683918). During the first embryonic mitotic division, involved in the formation of a functional microtubule organizing center provided by the male pronucleus (PubMed:11683918). 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). At the 2-cell stage embryo, localizes to the microtubule organizing center during mitotic metaphase. Localizes to the cytoplasm in germ cells and sperm, and to the nucleus in oocytes. Expressed in excretory cells, coelomocytes, head neurons, hypodermal cells, germ cells, oocytes, sperm and pharynx (at protein level). Expressed in embryos and adults. RNAi-mediated knockdown causes embryonic lethality. Embryos have impaired cleavage after fertilization and a failure to form a functional paternal microtubule-organizing center (MTOC). Due to a lack of cytokinesis, embryos become multinucleated. Binds Ca(2+). Belongs to the peptidase C19 family.