hexosamines

Hexosamines are a class of amino sugars derived from hexose monosaccharides by replacing one hydroxyl group with an amino group. The typical structure is a 2-amino-2-deoxyhexose. Common examples include glucosamine, galactosamine, and mannosamine, as well as their N-acetyl derivatives such as N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc).

In biology, hexosamines are ubiquitous components of glycoproteins and glycolipids and are essential building blocks of glycosaminoglycans in connective tissue, including chondroitin sulfate and heparan sulfate. They also occur in bacterial cell walls as part of peptidoglycan, formed from N-acetylglucosamine linked to N-acetylmuramic acid, and in the chitin of fungal cell walls and arthropod exoskeletons as N-acetylglucosamine.

Biosynthesis occurs via the hexosamine biosynthesis pathway, beginning with fructose-6-phosphate and yielding UDP-activated forms such as UDP-N-acetylglucosamine. These activated donors serve in various glycosylation reactions, including N- and O-glycosylation of proteins and lipids, and contribute to the biosynthesis of glycoconjugates.

In research and medicine, hexosamines are studied for their roles in metabolism and disease. Glucosamine supplements are marketed for joint health, though clinical evidence regarding efficacy is variable. In laboratory contexts, hexosamine derivatives are common substrates and labeling reagents for glycosylation studies.