aminosugars

Aminosugars are monosaccharides in which one or more hydroxyl groups are replaced by an amino group. In many amino sugars, the amino group is later acetylated, giving N-acetyl derivatives such as N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine ( GalNAc). Other examples include glucosamine (GlcN) and galactosamine (GalN). These compounds occur in various biological contexts and contribute to structural and signaling roles in both microbes and animals. Chitin and its deacetylated form chitosan are polymers composed of N-acetylglucosamine units.

Biosynthesis and activated forms are central to their biological function. In many organisms, amino sugars derive from fructose-6-phosphate through a series of enzymatic steps that generate glucosamine-6-phosphate, which can be acetylated to N-acetylglucosamine-6-phosphate and subsequently converted to UDP-N-acetylglucosamine (UDP-GlcNAc). UDP-GlcNAc and UDP-N-acetylgalactosamine (UDP-GalNAc) serve as key activated sugar donors for the synthesis of glycoproteins, glycolipids, and glycosaminoglycans. In bacteria, GlcNAc and GalNAc units are essential components of peptidoglycan and capsule polysaccharides, while in eukaryotes GlcNAc is a major contributor to N-linked glycosylation and regulatory O-GlcNAc modification of proteins.

Functions and occurrences span various biological systems. Aminosugars form the building blocks of bacterial cell walls and are embedded in the extracellular matrix of animals as part of glycosaminoglycans such as heparan sulfate and chondroitin sulfate. In humans, GlcNAc residues play roles in protein folding, signaling, and cell recognition.

Applications and notes: glucosamine is used as a dietary supplement with disputed efficacy for osteoarthritis. Industrially, chitin and chitosan, comprising amino sugar derivatives, have wide uses in biomedicine, agriculture, and materials science.