Ubiquitin-protein hydrolase involved both in the processing of ubiquitin precursors and of ubiquitinated proteins. This enzyme is a thiol protease that recognizes and hydrolyzes a peptide bond at the C-terminal glycine of ubiquitin. 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 proteasome 19S subunit rpn-13. Highly expressed in intestine and to a lesser extent in other tissues including muscles and neurons. Expression decreases with age. RNAi-mediated knockdown causes a slight decrease in lifespan and in brood size. Enhanced proteasome activity, specifically in the intestine. Belongs to the peptidase C12 family.