NAcetylmannosamine

N-acetylmannosamine, commonly abbreviated ManNAc, is the N-acetyl derivative of the amino sugar mannosamine. It is an intermediate in the de novo biosynthesis of sialic acids and is soluble in water. As a monosaccharide derivative, it plays a central role in the production of the nine-carbon sialic acid family.

In humans and many other organisms, sialic acid biosynthesis begins with UDP-N-acetylglucosamine (UDP-GlcNAc). UDP-GlcNAc 2-epimerase converts it to N-acetylmannosamine, which is then phosphorylated by N-acetylmannosamine kinase to ManNAc-6-phosphate. ManNAc-6-phosphate condenses with phosphoenolpyruvate via N-acetylneuraminic acid synthase to form N-acetylneuraminic acid-9-phosphate, which is dephosphorylated to N-acetylneuraminic acid (Neu5Ac). Neu5Ac is subsequently activated to CMP-Neu5Ac for incorporation into glycoconjugates on glycoproteins and glycolipids. A similar pathway operates in many bacteria, contributing to their own sialic acid-containing molecules.

Biological function is tied to the widespread presence of sialic acids at cell surfaces, where they influence cell–cell interactions, receptor binding, and immune recognition. Because ManNAc is a key precursor, it is frequently used in biochemical research and glycoengineering. Analogues of ManNAc are employed to probe sialylation pathways and to label glycans in living systems.

See also: sialic acid biosynthesis, N-acetylneuraminic acid, CMP-sialic acid, glycosylation.