Catalytically inactive phosphatase. Belongs to the protein-tyrosine phosphatase family. Non-receptor class subfamily. Contains a Gly residue instead of a conserved Cys residue at position 120 in the dsPTPase catalytic loop which renders it catalytically inactive as a phosphatase (By similarity). The binding pocket is however sufficiently preserved to bind phosphorylated substrates, and may protect them from phosphatases (By similarity).