Preferentially dephosphorylates phosphatidylinositol 3-phosphate (PI3P), and has some activity towards phosphatidylinositol 3,5-bisphosphate (PI35P) (PubMed:18393358, PubMed:25124690). May also dephosphorylate proteins phosphorylated on Ser, Thr, and Tyr residues (By similarity). Positively regulates autophagy and is recruited to autophagosomes by PI3P where it catalyzes PI3P turnover to promote autophagosome maturation (PubMed:25124690). Thought to have a role in maintenance of muscle function (PubMed:18393358). Involved in locomotion and lifespan determination (PubMed:18393358). H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3,5-bisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-5-phosphate) + phosphate 1,2-dihexadecanoyl-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + H2O = 1,2-dihexadecanoyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate 1,2-dihexadecanoyl-sn-glycero-3-phospho-(1D-myo-inositol-3,5-phosphate) + H2O = 1,2-dihexadecanoyl-sn-glycero-3-phospho-(1D-myo-inositol-5-phosphate) + phosphate 1,2-dioctanoyl-sn-glycero-3-phospho-(1-D-myo-inositol-3-phosphate) + H2O = 1,2-dioctanoyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate Inhibited by sodium vanadate and peroxide. Expressed in the body wall muscle and in eggs (PubMed:18393358). Expressed in head neurons (PubMed:12788949). Expressed in the intestine (PubMed:18393358, PubMed:25124690). Expressed in pharyngeal cells, vulval muscle cells and cells of the tail region (PubMed:25124690). Expressed in most cells during embryogenesis (PubMed:25124690). Expressed most strongly in the egg with expression present in L1 but reducing through to L3 where it is very weak. No expression was found in L4. Strong expression is also seen in egg-laying adults and post-reproductive adults. Interacts with phosphatidylinositol 3-phosphate (PI3P) via the FYVE-type domain. Worms exhibit a 2-fold increase in PI3P, sluggish body movement with progressive deterioration and defects in gestation. Belongs to the protein-tyrosine phosphatase family. Non-receptor class myotubularin subfamily.