Has protein tyrosine phosphatase activity and may act as a virulence factor to support intracellular survival in host macrophages. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Activated in a reduced environment which promotes the reduction of the disulfide bond between the regulatory Cys-53 and catalytic Cys-114 residues. Optimum pH is 6. Enriched around the kinetoplast. Expressed at the promastigote life cycle stage during the logarithmic growth and the stationary phase (at protein level). Expressed at lower levels at the amastigote life cycle stage (at protein level). Belongs to the protein-tyrosine phosphatase family.