Enrichment of bis-(monoacylglyceryl) phosphate in lysosomes from rat liver.

The subcellular distribution in rat liver of a phospholipid identified as bis-(monoacylglyceryl) phosphate (bis(MAG)P) has been investigated. In liver from untreated animals, 48 % of bis(MAG)P was recovered in a crude mitochondrial fraction where it was enriched 2.8-fold over the homogenate in terms of protein. When liver from animals who had received Triton WR-1339 by injection 3 days earlier was taken and the crude mitochondrial fraction subfractionated on a discontinuous density gradient of sucrose, 32% of bis(MAG)P was recovered in the lysosome fraction. In terms of protein, bis(MAG)P was enriched 32-fold in the lysosome fraction and its distribution among the various fractions paralleled closely that of acid phosphatase. In the lysosome fraction it comprised 7% of the total phospholipid P whereas cardiolipin accounted for 1%. These results show that bis(MAG)P is greatly enriched in secondary lysosomes.