Dual specificity phosphatase that dephosphorylates MAP kinase MAPK1/ERK2 on both 'Thr-183' and 'Tyr-185', regulating its activity during the meiotic cell cycle. 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 Brain. High level expression seen in the cingulate gyrus within the retrospinal cortex, ventral and medial divisions of the anterior thalamus and the medial geniculate nucleus. Expressed at moderate levels in the parietal and temporal cortex. Expressed in the cerebellum. Exhibits night/day variations with a 100-fold increased expression at night in the pineal gland (at protein level). Up-regulation is due to a large degree to the release of norepinephrine from nerve terminals in the pineal gland and cAMP signaling pathway. Phosphorylation at Ser-359 and Ser-364 by MAPK1/ERK2 and MAPK3/ERK1 reduces its rate of degradation. Belongs to the protein-tyrosine phosphatase family. Non-receptor class dual specificity subfamily.