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.
undecaprenyldiphospho-muramoylpentapeptide beta-N-acetylglucosaminyltransferase. MurG (EC 2.4.1.227) is an N-acetylglucosaminyltransferase, the last enzyme involved in the intracellular phase of peptidoglycan biosynthesis. It transfers N-acetyl-D-glucosamine (GlcNAc) from UDP-GlcNAc to the C4 hydroxyl of a lipid-linked N-acetylmuramoyl pentapeptide (NAM). The resulting disaccharide is then transported across the cell membrane, where it is polymerized into NAG-NAM cell-wall repeat structure. MurG belongs to the GT-B structural superfamily of glycoslytransferases, which have characteristic N- and C-terminal domains, each containing a typical Rossmann fold. The two domains have high structural homology despite minimal sequence homology. The large cleft that separates the two domains includes the catalytic center and permits a high degree of flexibility.