Dephosphorylates phosphatidylinositol 3-phosphate (PI3P) and phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2). Negatively regulates accumulation of PI3P on intracellular vesicles (PubMed:19816564, PubMed:21490059). Negatively regulates phagocytosis of apoptotic cells probably by limiting the recruitment and/or the activation of ced-5, ced-2 and ced-12 complex (PubMed:19816564, PubMed:21490059). In addition, may positively regulate phagosome maturation by promoting recycling of apoptotic receptor ced-1 back to the plasma membrane (PubMed:21490059). Essential for embryonic and larval development (PubMed:19816564). May promote migration of distal tip cells (PubMed:19816564). 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-dioctanoyl-sn-glycero-3-phospho-(1-D-myo-inositol-3-phosphate) + H2O = 1,2-dioctanoyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate Transiently co-localizes with phagocytic receptor ced-1 at the pseudopods during phagocytosis of apoptotic cells. Expressed in embryo, larva and in adults (PubMed:19816564, PubMed:21490059). Expressed in a few head and tail neurons (PubMed:12788949). Expressed in hypodermis, body wall and pharyngeal muscles, sheath cells, vulva, distal tip cells and coelomocytes (PubMed:19816564, PubMed:21490059). The GRAM domain is required for localization to the plasma membrane. The myotubularin phosphatase domain is required for localization to the plasma membrane. RNAi-mediated knockdown causes an increase in PI3P levels in intracellular vesicles. Also causes an increase in germline cell corpse engulfment, although corpses fail to be cleared. RNAi-mediated knockdown in ced-1, ced-6, ced-2, ced-10 or ced-7 mutant background partially restores cell corpses engulfment. Belongs to the protein-tyrosine phosphatase family. Non-receptor class myotubularin subfamily.