The lipid composition of phosphorylating ‘digitonin particles’ and water- and saline-extracted mitochondria from rat liver

Abstract

The phospholipid and fatty acid composition of particles of rat-liver mitochondria prepared by the action of digitonin is described. The phospholipid fractions separated by silicic acid chromatography were all "lyso" compounds, the ratio of fatty acid to phosphorus approaching unity. Of the lipid phosphorus, 47% appeared in the choline-containing fraction and 14% in the polyglycerolphospholipid fraction. Of the fatty acids, 51% appeared in the choline-containing fraction and only 7.5% in the polyglycerolphospholipid fraction. A sample of digitonin particles contained 355 [mu]moles of phospholipid fatty acid/g. dry wt. and 34 [mu]moles of neutral-lipid fatty acid/g. dry wt. Arachidonic acid and linoleic acids were selectively retained by the digitonin particles, both in the neutral-lipid and phospholipid fractions. The insoluble residue of mitochondria remaining after treatment with water or saline contained a higher proportion of lipid than the original mitochondria. Free fatty acids were liberated from the mitochondria by the saline or water treatment. The relationship of mitochondrial lipids to the functions of the mitochondria is discussed.