DUSP21 (Dual specificity protein phosphatase 21) belongs to the protein-tyrosine phosphatase family. Dual specificity protein phosphatases(DUSPs) inactivate their target kinases by dephosphorylating both the phosphoserine/threonine and phosphotyrosine residues. This enzyme can dephosphorylate single and diphosphorylated synthetic MAPK peptides, with preference for the phosphotyrosine and diphosphorylated forms over phosphothreonine.