The reversible posttranslational modification of proteins by the addition of small ubiquitin-like SUMO proteins (see SUMO1; MIM 601912) is required for numerous biologic processes. SUMO-specific proteases, such as SENP5, are responsible for the initial processing of SUMO precursors to generate a C-terminal diglycine motif required for the conjugation reaction. They also have isopeptidase activity for the removal of SUMO from high molecular mass SUMO conjugates (Di Bacco et al., 2006 [PubMed 16738315]).