- Mannose is a six-carbon monosaccharide (hexose) with the molecular formula C₆H₁₂O₆. It is an aldohexose, meaning it contains an aldehyde functional group at the first carbon. Structurally, mannose is a C-2 epimer of glucose, differing only in the spatial arrangement of the hydroxyl group on the second carbon atom.
- Despite this subtle difference, mannose exhibits distinct biological properties and metabolic roles. Naturally, mannose occurs in free form in some fruits, such as cranberries and certain berries, but more commonly it is found as a constituent of plant polysaccharides and glycoproteins.
- In living systems, mannose plays an essential role in glycosylation, the process by which sugars are attached to proteins and lipids. N-linked glycosylation, for instance, often begins with mannose residues in the oligosaccharide precursor, which is critical for proper protein folding, stability, and function. Mannose-containing glycans are found on the cell surface, where they contribute to processes such as cell–cell recognition, immune signaling, and pathogen interaction. Some pathogens, including bacteria and viruses, exploit mannose residues on host cells for adhesion, highlighting its importance in host–pathogen interactions.
- Metabolically, mannose can be phosphorylated to mannose-6-phosphate, a key intermediate that enters the glycolytic pathway after conversion to fructose-6-phosphate. Mannose-6-phosphate is also vital in the lysosomal enzyme targeting system, where it acts as a recognition marker directing hydrolase enzymes to lysosomes. This pathway underscores the significance of mannose in cellular homeostasis and intracellular trafficking. Defects in this system lead to lysosomal storage diseases such as I-cell disease (mucolipidosis II), illustrating the biomedical importance of mannose-related pathways.
- From a health perspective, D-mannose supplements have attracted attention for their therapeutic potential, particularly in the prevention and management of urinary tract infections (UTIs). D-mannose is thought to inhibit the adhesion of uropathogenic Escherichia coli to the bladder epithelium by competitively binding to bacterial fimbriae, thereby reducing infection risk. Beyond this, ongoing research is exploring the role of mannose in modulating immune responses and its potential use in cancer therapy, as tumor cells often exhibit altered glycosylation patterns involving mannose residues.
- Industrially, mannose and mannose-rich polysaccharides are valued in biotechnology and pharmaceuticals. Mannose derivatives serve as precursors for specialized biochemicals, and mannose-based glycans are being studied for vaccine development, drug delivery systems, and biomaterial design. Its availability from renewable biomass sources also makes mannose an attractive feedstock for sustainable bioprocesses.
