Protein tyrosine-protein phosphatase required for T-cell activation through the antigen receptor. Acts as a positive regulator of T-cell coactivation upon binding to DPP4. The first PTPase domain has enzymatic activity, while the second one seems to affect the substrate specificity of the first one. Upon T-cell activation, recruits and dephosphorylates SKAP1 and FYN (By similarity). Dephosphorylates LYN, and thereby modulates LYN activity. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Interacts with SKAP1. Interacts with DPP4; the interaction is enhanced in an interleukin-12-dependent manner in activated lymphocytes (By similarity). Binds GANAB and PRKCSH. Colocalized with DPP4 in membrane rafts. Expression is restricted to the hematopoietic compartment of development. The first PTPase domain interacts with SKAP1. Heavily N- and O-glycosylated. Belongs to the protein-tyrosine phosphatase family. Receptor class 1/6 subfamily. It is uncertain whether Met-1 or Met-3 is the initiator. Truncated N-terminus. Truncated N-terminus. Contaminating sequence. Sequence of unknown origin in the N-terminal part. Truncated N-terminus. Truncated N-terminus.