Protein tyrosine phosphatase which stimulates progression from G1 into S phase during mitosis. Inhibits geranylgeranyl transferase type II activity by blocking the association between RABGGTA and RABGGTB (By similarity). H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Inhibited by sodium orthovanadate and pentamidine. In contrast to PTP4A1 and PTP4A3, does not interact with tubulin. Interacts with RABGGTB (By similarity). Expressed in skeletal muscle, and at lower levels in liver, lung, heart, kidney, brain, testis and spleen. Farnesylated. Farnesylation is required for membrane targeting and for interaction with RABGGTB (By similarity). Belongs to the protein-tyrosine phosphatase family.