The lipid composition of flight muscle mitochondria isolated from the blowfly, Phormia regina

The role of lipids in membrane structure and function was studied by measuring the major lipid classes in mitochondria isolated from flight muscle of the blowfly, Phormia regina. Approximately 98% of the total lipid is phospholipid. Neutral lipid constitutes the remaining 2% of the total. Phosphatidylethanolamine accounts for 55-60% of the phospholipid. A molecular ratio of 4:1:1 is found for phosphatidylethanolamine, phosphatidylcholine, and cardiolipin (diphosphatidylglycerol). The neutral lipids include cholesterol, about 20%, and quinone, 40-45% of the total. The free fatty acid content of the neutral lipid fraction is variable, apparently being generated by endogenous phospholipase activity. The fatty acids of the neutral and phospholipid classes are predominantly 14-18 carbon acids; long-chain fatty acids of 20 and 22 carbons are essentially absent. The neutral lipid fraction contains 43% saturated and 51% monoenoic fatty acids. More than 65% of the phospholipid fatty acids are unsaturated. The principal fatty acids are palmitic, palmitoleic, oleic, linoleic, and linolenic. No trace of α- or β-tocopherol is detected. As vitamin E is considered an important naturally occuring antioxidant that prevents lipid peroxidation, the apparent absence of α- and β-tocopherol in these mitochondria coupled with intense oxidative activity of the mitochondria leads to the suggestion that blowfly flight muscle mitochondria may be particularly susceptible to peroxidative damage.