CDP‐diacylglycerol synthesis in rat liver mitochondria

CDP-diacylglycerol for polyglycerophosphatide biogenesis can be synthesized within rat liver mitochondria. This membrane-associated enzyme was predominantly located in the inner mitochondrial membrane. GTP had a significant effect in activating the microsomal CDP-diacylglycerol synthase, especially if the microsomes were preincubated with GTP in the presence of phosphatidic acid. This stimulatory effect of GTP on the microsomal enzyme was not detected in the mitochondrial fractions. The enzymes could be solubilized from the membrane fractions using CHAPS, and the detergent-soluble activity partially restored by addition of phospholipids. Mitochondrial and microsomal CDP-diacylglycerol synthase activity could be completely separated by anion-exchange column chromatography. The mitochondrial and microsomal CDP-diacylglycerol synthases appear to be two distinct enzymes with different localization and regulatory characteristics.