PTP (2-315)/PTPN2

T-cell protein tyrosine phosphatase (TC-PTP), also known as PTPT and PTPN2, is an enzyme that removes phosphate groups covalently attached to tyrosine residues in proteins. This enzyme has two C-terminal end splice variants with distinctly different subcellular localizations. The shorter 45 kilodalton isoform is exclusively nuclear in resting cells, but redistrubutes to the cytosol upon stimulation with growth factors 1 and cellular stress 2 . The longer 48 kilodalton isoform is exclusively found in the endoplasmic reticulum 3 and seems to have distinctly different physiologic substrates from the smaller isoform. 1, 4 Although found in many cell types and tissues, TC-PTP is particularly prominent in hemopoietic cell types. 5, 6 Knockout mice lacking TC-PTP are born viable but die 3 to 5 weeks after birth of erythropoietic and lymphopoietic deficits 7 , indicating a critical role for TC-PTP in bone marrow maturation. TC-PTP will dephosphorylate a wide range of phosphoproteins, such as p52 Shc 6 and receptors for EGF 1 , Insulin 8 and growth hormone. 6 The recombinant protein lacks the C-terminal 100 amino acids that determine intracellular localization but is fully active. 9