Dual specificity phosphatase that dephosphorylates MAPK8/JNK and MAPK14/p38, but not MAPK1/ERK2, in vitro (By similarity). Exhibits intrinsic phosphatase activity towards both phospho-seryl/threonyl and -tyrosyl residues, with similar specific activities in vitro (PubMed:10585869). H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Most abundantly expressed in the testis. Not detectable in testis in the first 3 weeks of life. The expression markedly increases at approximately the 3rd week after birth and continues to increase gradually into adulthood. Produced by alternative promoter usage. Belongs to the protein-tyrosine phosphatase family. Non-receptor class dual specificity subfamily.