Mannose

    Mannose is a sugar monomer of the hexose series of carbohydrates.

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Metabolism

Mannose enters the carbohydrate metabolism stream in two steps:

• First it undergoes phosphorylation to mannose-6-phosphate by hexokinase.
• Then, it is converted to fructose-6-phosphate by mannose phosphate isomerase.

Formation

Mannose can be formed by the oxidation of mannitol.

It can also be formed from D-glucose in the Lobry-de Bruyn-van Ekenstein transformation

Etymology

The root of both "mannose" and "manitol" is manna, which the Bible records as the food supplied to the Israelites during their journey through the Sinai Peninsula. Manna is a sweet secretion of several trees and shrubs, such as Fraxinus ornus.

Cranberry juice

D-Mannose, which appears in some fruits including cranberry, has been postulated to prevent the adhesion of bacteria to the epithelium of the urinary tract and Urinary bladder through a mechanism presumed to be competitive in nature with the polysaccharide coating of the cystic epithelium. While no studies have objectively verified this mechanism, anecdotal reports from patients show some improvement in symptoms.^{[citation needed]}

Configuration

The fact that D-mannose has the same configuration at its penultimate carbon as D-glyceraldehyde is unsurprising as that is what defines the dextro classification. However, mannose differs from D-glucose by inversion of the C2 chiral centre. This apparently simple change leads to the drastically different chemistry of the two hexoses, as it does the remaining six hexoses.

See also

• Glycosylation
• alpha-Mannosidase
• Hexose
• Mannose receptor

References