Has phosphatase activity with synthetic phosphatase substrates and negatively regulates mitogen-activated protein kinase activity, presumably by catalysing their dephosphorylation (PubMed:7561881). Expected to display protein phosphatase activity toward phosphotyrosine, phosphoserine and phosphothreonine residues (Probable). 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 Monomer. Expressed predominantly in brain and lung. Belongs to the protein-tyrosine phosphatase family. Non-receptor class dual specificity subfamily.