N-acetylmannosamine

N-acetylmannosamine (ManNAc) is a monosaccharide derivative that plays a key role in the biosynthesis of glycoproteins and glycolipids. It is an important precursor in the sialic acid biosynthetic pathway, which is critical for cellular functions such as cell adhesion and signal transduction.

Structure and Properties

N-acetylmannosamine is a hexosamine sugar, composed of a six-carbon sugar backbone with an amino group at the second carbon and an acetyl group at the nitrogen. The structure of ManNAc is similar to that of mannose, but with an acetyl group replacing one of the hydroxyl groups.

Biosynthesis

N-acetylmannosamine is synthesized from fructose-6-phosphate and glutamine in a two-step reaction catalyzed by the enzyme glutamine:fructose-6-phosphate aminotransferase (GFAT). The product of this reaction, glucosamine-6-phosphate, is then acetylated by the enzyme glucosamine-6-phosphate N-acetyltransferase to produce N-acetylglucosamine-6-phosphate, which is isomerized to ManNAc.

Biological Role

ManNAc is a key intermediate in the biosynthesis of sialic acids, a family of nine-carbon sugars that are commonly found at the outermost end of glycan chains on the cell surface. Sialic acids play crucial roles in a variety of biological processes, including cell-cell interactions, immune responses, and pathogen recognition.

Clinical Significance

Defects in the metabolism of ManNAc and sialic acids are associated with a number of human diseases, including congenital disorders of glycosylation, sialuria, and certain types of cancer. In addition, ManNAc and its derivatives have been explored as potential therapeutic agents for these and other conditions.

See Also

• Sialic acid
• Glycosylation
• Congenital disorders of glycosylation
• Sialuria