Catalyzes the key rate-limiting step in the CDP-choline pathway for phosphatidylcholine biosynthesis. Catalyzes the key rate-limiting step in the CDP-choline pathway for phosphatidylcholine biosynthesis. CTP + H(+) + phosphocholine = CDP-choline + diphosphate Phospholipid metabolism; phosphatidylcholine biosynthesis; phosphatidylcholine from phosphocholine: step 1/2. Homodimer. Highly expressed in testis, placenta, brain, ovary, liver and fetal lung. Expressed in brain, liver and fetal lung. Phosphorylated. Extensively phosphorylated. Belongs to the cytidylyltransferase family.