CMP-NeuAc_Synthase activates N-acetylneuraminic acid by adding CMP moiety.
CMP-N-acetylneuraminic acid synthetase (CMP-NeuAc synthetase) or acylneuraminate cytidylyltransferase catalyzes the transfer the CMP moiety of CTP to the anomeric hydroxyl group of NeuAc in the presence of Mg++. It is the second to last step in the sialylation of the oligosaccharide component of glycoconjugates by providing the activated sugar-nucleotide cytidine 5'-monophosphate N-acetylneuraminic acid (CMP-Neu5Ac), the substrate for sialyltransferases. Eukaryotic CMP-NeuAc synthetases are predominantly located in the nucleus. The activated CMP-Neu5Ac diffuses from the nucleus into the cytoplasm.