Regulates mitogenic signal transduction by dephosphorylating both Thr and Tyr residues on MAP kinases ERK1 and ERK2. 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 Hollow spherical complex composed of 24 subunits with pseudooctahedral symmetry, has a tetramer as the basic unit. Phosphorylation in the C-terminus by ERK1/2 inhibits proteasomal degradation and stabilizes the protein. Belongs to the protein-tyrosine phosphatase family. Non-receptor class dual specificity subfamily.