Catalyzes the conversion of phosphatidic acid (PA) to CDP-diacylglycerol (CDP-DAG), an essential intermediate in the synthesis of phosphatidylglycerol, cardiolipin and phosphatidylinositol (PubMed:25375833). Exhibits specificity for the nature of the acyl chains at the sn-1 and sn-2 positions in the substrate, PA and the preferred acyl chain composition is 1-stearoyl-2-arachidonoyl-sn-phosphatidic acid (PubMed:25375833). Plays an important role in regulating the growth and maturation of lipid droplets which are storage organelles at the center of lipid and energy homeostasis (PubMed:26946540, PubMed:31548309). a 1,2-diacyl-sn-glycero-3-phosphate + CTP + H(+) = a CDP-1,2-diacyl-sn-glycerol + diphosphate 1-octadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphate + CTP + H(+) = 1-octadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate 1-octadecanoyl-2-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphate + CTP + H(+) = 1-octadecanoyl-2-(9Z,12Z-octadecadienoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-phosphate + CTP + H(+) = 1-hexadecanoyl-2-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate 1,2-di-(5Z,8Z,11Z,14Z)-eicosatetraenoyl-sn-glycero-3-phosphate + CTP + H(+) = 1,2-di-(5Z,8Z,11Z,14Z-eicosatetraenoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate 1-octadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phosphate + CTP + H(+) = 1-octadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate 1-octadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-phosphate + CTP + H(+) = 1-octadecanoyl-2-(4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate 1,2-di-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphate + CTP + H(+) = 1,2-di-(9Z,12Z-octadecadienoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphate + CTP + H(+) = 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-cytidine-5'-diphosphate + diphosphate Inhibited by its anionic phospholipid end products, with phosphatidylinositol-(4,5)- bisphosphate (PIP2) showing the strongest inhibition. Inhibition is also acyl chain specific, with 1-stearoyl-2-arachidonoyl-snphosphatidylinositol showing the strongest inhibition. Phospholipid metabolism; CDP-diacylglycerol biosynthesis; CDP-diacylglycerol from sn-glycerol 3-phosphate: step 3/3. Homodimer. Widely expressed. Expressed in heart, brain and retina, and to a lesser extent in placenta, lung, liver, skeletal muscle, kidney and pancreas. No expression detected at E10.5 in the developing brain. At E12.5 expression is detected in the developing sentral nervous system and peripheral nervous system. At E17.5 high levels of expression are detected in a number of sites, including the dorsal root ganglia of the peripheral nervous system and the ganglion cell layer of the neural retina in the developing eye. At this stage expression in the brain is restricted to the ventricular zone of the telencephalon, in particular in the basal ganglia and the cerebral cortex. Belongs to the CDS family.