Glycerophospholipid is a major class of lipids in cell membranes. Defects in their breakdowns are implicated in the pathogenesis of major diseases including cancer, neuronal, and lysosomal storage disorders. The products of glycerophospholipid breakdowns are known as Glycerophosphodiesters (GPDs). GPDs accumulate in lysosomes derived from models of Batten disease, a life-limiting lysosomal storage disorder whose pathological mechanism remains elusive and has no cure. The enzymes that degrade glycerophospholipid to GPDs are called phospholipases. Despite its fundamental role in membrane lipid turnover, the phospholipases that degrade glycerophospholipids in the lysosome are yet to be determined. I will leverage genetic and lipid biochemistry approaches to identify and characterize the exact machinery responsible for glycerophospholipid degradation in the lysosome. This will provide novel insights into the pathway of phospholipid metabolism and identify a potential therapeutic target in phospholipid-associated diseases such as Batten disease.