Hydrolyzes the inositol phosphate linkage of glycosylphosphatidylinositol (GPI)-anchored membrane proteins, thereby releasing them from the cell surface. Cleaves on the inositol side of the anchor, leaving the phosphate group attached to the membrane (PubMed:17720976, PubMed:2760042). This release of GPI-anchored proteins can modulate diverse biological processes, including the activation of signaling pathways (PubMed:17720976). . This is the function of GPLD1 (glycosylphosphatidylinositol specific phospholipase D1, ENSG00000112293).