May regulate the activity of several effector molecules involved in synaptic plasticity and neuronal cell survival, including MAPKs, Src family kinases and NMDA receptors. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Expressed in the central nervous system except in the cerebellum. Enriched within the striatum relative to other brain areas. Phosphorylation at Ser-49 by PKA deactivates PTPN5. Phosphorylation at Thr-59 and Ser-72 by MAPKs stabilizes the phosphatase, dephosphorylation of these sites results in ubiquitin-mediated degradation of the active phosphatase (By similarity). Belongs to the protein-tyrosine phosphatase family. Non-receptor class subfamily.