Sialic acid
Sialic acid is synthesized by glucosamine 6 phosphate and acetyl-CoA through a transferase, resulting in "N"-acetylglucosamine-6-P. This becomes "N"-acetylmannosamine-6-P through epimerization, which reacts with phosphoenolpyruvate producing "N"-acetylneuraminic-9-P (sialic acid). For it to become active to enter in the oligosaccharide biosynthesis process of the cell, a monophosphate nucleoside is added, which comes from a cytidine triphosphate, turning sialic acid into cytidine monophosphate-sialic acid (CMP-sialic acid). This compound is synthesized in the nucleus of the animal cell.