Recognizes and hydrolyzes the peptide bond at the C-terminal Gly of ubiquitin. Involved in the processing of poly-ubiquitin precursors as well as that of ubiquitinated proteins. Involved in salt tolerance by modulating sodium transport activity and repressing cell death at least partially through modulating SHM1 stability and activity (PubMed:23232097). Involved in cadmium tolerance by interacting with HIPP27 and probably modulating its stability (PubMed:23857362). 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 SHM1 and SHM4 (PubMed:23232097). Interacts with HIPP27 (PubMed:23857362). Expressed in flowers, siliques, rosette leaves, cauline leaves, stems and at a lower level in roots. In roots, expressed in the sieve elements. Regulated by the transcription factors NAC045 and NAC086 and up-regulated by salt stress. Exhibits reduced salt tolerance. Reduced shoot growth in response to salt stress. Belongs to the peptidase C19 family.