esterifi ed with fatty acids. The stereochemical confi guration of BMP differs as each glycerol moiety is esterifi ed through only the sn 1 position to the phosphate and contains a single fatty acid ( 1 ). Evidence suggests that BMP is synthesized from its structural isomer, phosphatidylglycerol ( 2 ). The fatty acid from the sn 2 position is removed with phospholipase A2 to produce lysophosphatidylglycerol, which then undergoes a transacylation reaction on the sn 2 position of the glycerol head group ( 3, 4 ). The subsequent steps, which must remove the fatty acid from the sn 1 position, rearrange the phosphoryl ester from the sn 3 to the sn 1 position and esterify the sn 2 position to produce the fi nal product, BMP, have not yet been adequately described. The synthesis of BMP is believed to occur in the lysosomal network, as BMP is highly enriched in the internal membranes of lysosomes ( 5 ).The negative charge of BMP, coupled with its proposed cone-shaped structure, enables it to participate in the organization of the membranes of the lysosomal network, contributing to its multivesicular/multilamellar morphology ( 6, 7 ). These properties of BMP also facilitate lysosomal lipid degradation, which takes place on the surface of the inner membranes of lysosomes. At the acidic pH of the lysosome, BMP contributes its negative charge to enhance adherence of the polycationic enzymes and activator proteins, aiding in lipid hydrolysis ( 8 ). Together, the high BMP and low cholesterol content of the internal lysosomal membrane ensures the selective degradation of lipids destined for lysosomal degradation without affecting the limiting membrane of the lysosome ( 9 ). Bis(monoacylglycero)phosphate (BMP) belongs to the group of glycerophospholipids that consist of a glycerol-3-phosphate backbone whose sn 1 and sn 2 positions are