DUSP21 is a member of the protein-tyrosine phosphatase family. DUSPs inactivate their target kinases by dephosphorylating both the phosphoserine/threonine and phosphotyrosine residuesb. DUSP21 is able to dephosphorylate single and diphosphorylated synthetic MAPK peptides， favoring the phosphotyrosine and diphosphorylated forms over phosphothreonine. DUSP21 is only expressed in testis where there are dephosphorylated phosphotyrosine residues in MAPK peptides.
