Hydrolase that can remove conjugated ubiquitin from proteins in vitro and may therefore play an important regulatory role at the level of protein turnover by preventing degradation (Probable). Inactive cysteine protease (PubMed:24659992). Deubiquitinating enzyme which regulates gene expression by contributing to chromatin organization and DNA methylation patterns (e.g. H3K4me3 and H3K27me3) (PubMed:29061907). Involved in the interpretation of environmental information, probably by altering chromatin organization and maintaining redox homeostasis (PubMed:29301952). Required for phosphate (Pi) homeostasis (e.g. responses upon Pi starvation including DNA methylation and histone methylation) (PubMed:29061907, PubMed:29301952). Negative regulator of root hair morphogenesis (PubMed:29301952). 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). Altered DNA methylation of root hair-related genes and altered phosphate (Pi)-responsive root traits (PubMed:29061907). Abnormal responses upon Pi starvation leading to the formation of very short root hairs instead of increased lateral root formation and increased root hair length (PubMed:29061907). On low-Pi media, altered H3K4 and H3K27 trimethylation levels at the transcriptional start site of a subset of genes encoding key players in Pi homeostasis thus leading to a reduced transcription of these genes (PubMed:29061907, PubMed:29301952). Under Pi-replete conditions, constitutive Pi deficiency root phenotype such as attenuated primary root growth associated with increased root hairs development (PubMed:29061907, PubMed:29301952). Accumulation of proteins involved in chromatin remodeling and altered distribution of reactive oxygen species along the root (PubMed:29301952). Belongs to the peptidase C85 family.