PHOSPHOLIPID SYNTHESIS IN RAT LIVER MITOCHONDRIA

1. 1. Synthesis of phospholipids in isolated rat liver mitochondria was studied by measuring the incorporation into mitochondrial lipids of glycerol 3-[32P]phosphate and [14C]palmitic acid. 2. 2. Both precursors were incorporated chiefly into phosphatidic acid. Under experimental conditions this incorporation was much higher in mitochondria than in microsomes. 3. 3. Maximum esterification of glycerol 3-[32P]phosphate was obtained with palmitic acid and was less pronounced with acids of shorter or longer carbon atom chains. Elaidic acid was inhibitory. 4. 4. ATP either added or generated intramitochondrially was required. However, in the presence of carnitine esters of long-chain fatty acids the incorporation of glycerol 3-[32P]phosphate was independent of ATP. 5. 5. With internally formed ATP, the synthesis of phosphatidic acid was inhibited by atractyloside but was unaffected by this glycoside with external ATP or with palmitoyl carnitine. 6. 6. Outer and inner mitochondrial membranes were separated by two different procedures. The esterification of glycerol 3-[32P]phosphate by free fatty acids in the presence of ATP and CoA was much higher, on a protein basis, in the outer than in the inner membrane fractions. A substantial esterification by palmitoyl carnitine occurred, however, only in unfractionated membranes and was low in both the outer and the inner membrane fractions examined separately. © 1969.