Cytidine 5'-triphosphate (CTP) is a pyrimidine nucleoside triphosphate that is involved in a variety of biochemical reactions. It is used in the synthesis of RNA by RNA polymerases. In the formation of phosphatidylcholine (PC), CTP reacts with phosphocholine, via CTP:phosphocholine cytidylyltransferases, to produce CDP-choline and diphosphate.[1],[2] This is the rate-limiting step in PC synthesis and, as a pivotal step in cell proliferation, can be important in cancer.[3] CTP also interacts with N-acylneuraminate, in a reaction mediated by N-acylneuraminate cytidylyltransferase, to generate an intermediate that is required for sialylation, namely CMP-N-acylneuraminic acid.[4]

Reference:
[1]. Li, Z., and Vance, D.E. Phosphatidylcholine and choline homeostasis. Journal of Lipid Research 49, 1187-1194 (2008).
[2]. Lagace, T.A., and Ridgway, N.D. The role of phospholipids in the biological activity and structure of the endoplasmic reticulum. Biochim.Biophys.Acta. 1833, 2499-2510 (2013).
[3]. Arsenault, D.J., Yoo, B.H., Rosen, K.V., et al. ras-Induced up-regulation of CTP:phosphocholine cytidyltransferase a contributes to malignant transformation of intestinal epithelial cells. The Journal of Biological Chemisty 288(1), 633-643 (2013).
[4]. Vionnet, J., Concepcion, N., Warner, T., et al. Purification of CMP-N-acetylneuraminic acid synthetase from bovine anterior pituitary glands. Glycobiology 9(5), 481-487 (1999).