The function of MTMR8 (myotubularin related protein 8, Ensembl gene identifier ENSG00000102043) is as follows. Lipid phosphatase that specifically dephosphorylates the D-3 position of phosphatidylinositol 3-phosphate and phosphatidylinositol 3,5-bisphosphate, generating phosphatidylinositol and phosphatidylinositol 5-phosphate (PubMed:22647598, PubMed:26143924). In complex with MTMR9, negatively regulates autophagy (PubMed:22647598). .