Possesses phosphotyrosine phosphatase activity in vitro. Hydrolyzes para-nitrophenyl phosphate in vitro (PubMed:21409566, PubMed:18433060). Hydrolyzes O-methylfluorescein phosphate in vitro (PubMed:21409566). Hydrolyzes polyphosphate and ATP in vitro (PubMed:18433060). Dephosphorylates the phosphoinositides PI(3,4,5)P3, PI(3,5)P2, but not PI(3)P, PI(3,4)P2 or PI(4,5)P2 (PubMed:17976645). H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Optimum pH is 5.0 (with polyphosphate as substrate). Homomultimer (Probable). Homodimer and homohexamer (PubMed:18433060). A number of isoforms are produced. According to EST sequences. Highly expressed in siliques and at lower levels in roots, leaves and flowers. Belongs to the protein-tyrosine phosphatase family.