Mannose is a sugar

Sugar

Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

 monomer

Monomer

A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

 of the aldohexose

Hexose

In organic chemistry, a hexose is a monosaccharide with six carbon atoms, having the chemical formula C6H12O6. Hexoses are classified by functional group, with aldohexoses having an aldehyde at position 1, and ketohexoses having a ketone at position 2....

 series of carbohydrate

Carbohydrate

A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

s. Mannose is a C-2 epimer

Epimer

In chemistry, epimers are diastereomers that differ in configuration of only one stereogenic center. Diastereomers are a class of stereoisomers that are non-superposable, non-mirror images of one another....

 of glucose

Glucose

Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

. It is not part of human metabolism, but is a component of microbial cell walls, and is therefore a target of the immune system and also of antibiotics.

Structure

Two of the cyclic mannose isomer

Isomer

In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...

s possess a pyranose

Pyranose

Pyranose is a collective term for carbohydrates that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom. The name derives from its similarity to the oxygen heterocycle pyran, but the pyranose ring does not have double bonds...

 (six-membered) ring, while the other two possess a furanose

Furanose

A furanose is a collective term for carbohydrates that have a chemical structure that includes a five-membered ring system consisting of four carbon atoms and one oxygen atom...

 (five-membered) ring.

D-Mannose isomers
Skeletal formula Skeletal formula The skeletal formula of an organic compound is a shorthand representation of its molecular structure, developed by the organic chemist, Friedrich August Kekulé von Stradonitz. Skeletal formulae are ubiquitous in organic chemistry, because they are relatively quick and simple to draw. Carbon and...	Haworth projection Haworth projection A Haworth projection is a common way of representing the cyclic structure of monosaccharides with a simple three-dimensional perspective.The Haworth projection was named after the English chemist Sir Norman Haworth....
	α-D-Mannofuranose <1 %	β-D-Mannofuranose <1 %
	α-D-Mannopyranose 67 %	β-D-Mannopyranose 33 %

Metabolism

Mannose is not well metabolized in humans.
Therefore, it does not significantly enter the carbohydrate metabolism when taken orally, and although traces of exogeneously introduced mannose have been detected in all body tissues, using radioactive markers, in a well hydrated mammal, 90% of mannose ingested is excreted unconverted into the urine within 30 – 60 minutes, with 99% of the remainder being excreted within the following 8 hours. There is no significant increase in blood-glucose levels during this time.

Mannose is present in numerous glycoconjugates including N-linked glycosylation of proteins. C-mannosylation is also abundant and can be found in collagen-like regions. Mannose is a C-2 epimer

Epimer

In chemistry, epimers are diastereomers that differ in configuration of only one stereogenic center. Diastereomers are a class of stereoisomers that are non-superposable, non-mirror images of one another....

 of glucose and displays a pucker in the solution ring form.

Recombinant proteins produced in yeast may be subject to mannose addition in patterns different from those used by mammalian cells. This difference in recombinant proteins from those normally produced in mammalian organisms may influence the effectiveness of vaccines.

Formation

Mannose can be formed by the oxidation of mannitol

Mannitol

Mannitol is a white, crystalline organic compound with the formula . This polyol is used as an osmotic diuretic agent and a weak renal vasodilator...

.

It can also be formed from glucose

Glucose

Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 in the Lobry-de Bruyn-van Ekenstein transformation

Lobry-de Bruyn-van Ekenstein transformation

In carbohydrate chemistry, the Lobry–de Bruyn–van Ekenstein transformation also known as the Lobry–de Bruyn–van-Alberda–van-Ekenstein transformation is the base or acid catalyzed transformation of an aldose into the ketose isomer or vice versa, with a tautomeric enediol as reaction intermediate....

D-mannose is sold as a naturopathic remedy for urinary tract infections, and it is claimed to work through the disruption of adherence of bacteria in the urinary tract.

Etymology

The root of both "mannose" and "mannitol" is manna

Manna

Manna or Manna wa Salwa , sometimes or archaically spelled mana, is the name of an edible substance that God provided for the Israelites during their travels in the desert according to the Bible.It was said to be sweet to the taste, like honey....

, which the Bible

Bible

The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

 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

Fraxinus ornus

Fraxinus ornus is a species of Fraxinus native to southern Europe and southwestern Asia, from Spain and Italy north to Austria and the Czech Republic, and east through the Balkans, Turkey, and western Syria to the Lebanon.It is a medium-sized deciduous tree growing to 15–25 m tall with a trunk up...

.

Configuration

Mannose differs from glucose by inversion of the C-2 chiral center. This apparently simple change leads to the drastically different chemistry of the two hexoses, as it does the remaining six aldohexoses.