PTPN4 also known as Protein tyrosine phosphatase, non-receptor type 4, is a member of the protein tyrosine phosphatase (PTP) family. PTPs are known to be signaling molecules that regulate a variety of cellular processes including cell growth, differentiation, mitotic cycle, and oncogenic transformation. PTPN4 is a widely expressed non-receptor protein tyrosine phosphatase. It has been shown to interact with glutamate receptor delta 2 and epsilon, and may affect glutamate receptors signaling and/or in regulation of their activities through tyrosine dephosphorylation. Recombinant human PTPN4, fused to His-tag at N-terminus, was expressed in E.coli