Enables phosphatidylinositol-3-phosphatase activity. Predicted to be involved in phosphatidylinositol dephosphorylation and regulation of phosphatidylinositol dephosphorylation. Predicted to act upstream of or within lipid metabolic process. Located in cytoplasm and plasma membrane. Is expressed in several structures, including alimentary system; brain; genitourinary system; integumental system; and sensory organ. Orthologous to human MTMR1 (myotubularin related protein 1). [provided by Alliance of Genome Resources, Apr 2022]