Lipase which is essential for lysis of subvacuolar cytoplasm to vacuole targeted bodies and intravacuolar autophagic bodies. Involved in the lysis of intravacuolar multivesicular body (MVB) vesicles. The intravacuolar membrane disintegration by ATG15 is critical to life span extension (By similarity). a triacylglycerol + H2O = a diacylglycerol + a fatty acid + H(+) Binds to both phosphatidylinositol (PI) and phosphatidylinositol 3,5-bisphosphate (PIP2). From ER, targeted to vacuolar lumen at the MVB vesicles via the Golgi and the prevacuolar compartment (PVC). Belongs to the AB hydrolase superfamily. Lipase family.