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Mannose is a
sugar Sugar is the generic name for , soluble s, many of which are used in food. Simple sugars, also called s, include , , and . Compound sugars, also called s or double sugars, are molecules made of two monosaccharides joined by a . Common examp ...

sugar
monomerA monomer ( ; '' mono-'', "one" + '' -mer'', "part") is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrical ...

monomer
of the
aldohexose In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, mo ...
series of
carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common ex ...
s. It is a C-2
epimerIn stereochemistry, an epimer is one of a pair of diastereomer Diastereomers (sometimes called diastereoisomers) are a type of a stereoisomer. Diastereomers are defined as non-mirror image non-identical stereoisomers. Hence, they occur when two or m ...
of
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
. Mannose is important in human
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as Cell signaling, signaling and self-sustaining ...

metabolism
, especially in the
glycosylation Glycosylation (see also chemical glycosylationA chemical glycosylation reaction involves the coupling of a glycosyl donor, to a glycosyl acceptor forming a glycoside. If both the donor and acceptor are sugars, then the product is an oligosacchar ...

glycosylation
of certain
protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one location to another. Proteins differ from one another primarily ...

protein
s. Several congenital disorders of glycosylation are associated with mutations in
enzyme Enzymes () are s that act as s (biocatalysts). Catalysts accelerate . The molecules upon which enzymes may act are called , and the enzyme converts the substrates into different molecules known as . Almost all in the need in order to occu ...

enzyme
s involved in mannose metabolism. Mannose is not an
essential nutrient A nutrient is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and ta ...
; it can be produced in the human body from glucose, or converted into glucose. Mannose provides 2–5 
kcal The calorie is a unit of energy As energy In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, i ...
/g. It is partially excreted in the
urine Urine is a liquid by-product A by-product or byproduct is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced. A by-product can be useful and ...

urine
.


Structure

Mannose commonly exists as two different-sized rings, the
pyranosePyranose is a collective term for saccharides that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom. There may be other carbons external to the ring. The name derives from its similarity ...
(six-membered) form and the
furanose A furanose is a collective term for carbohydrates is a disaccharide found in animal milk. It consists of a molecule of galactose, D-galactose and a molecule of glucose, D-glucose bonded by beta-1-4 glycosidic linkage. A carbohydrate () is a bio ...
(five-membered) form. Each ring closure can have either an alpha or beta configuration at the
anomer An anomer is a type of geometric variation found at certain atoms in carbohydrate is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage. A carboh ...
ic position. The chemical rapidly undergoes
isomerization In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a ...
among these four forms.


Metabolism

While much of the mannose used in glycosylation is believed to be derived from glucose, in
cultured
cultured
hepatoma Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer Liver cancer (also known as hepatic cancer, primary hepatic cancer, or primary hepatic malignancy) is cancer that starts in the liver. Liver cancer can be primary (star ...
cells (cancerous cells from the liver), most of the mannose for glycoprotein biosynthesis comes from extracellular mannose, not glucose. Many of the glycoproteins produced in the liver are secreted into the bloodstream, so dietary mannose is distributed throughout the body. 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. The digestion of many polysaccharides and glycoproteins yields mannose, which is phosphorylated by
hexokinase A hexokinase is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the e ...
to generate mannose-6-phosphate. Mannose-6-phosphate is converted to
fructose-6-phosphate Fructose 6-phosphate (sometimes called the Neuberg ester) is a derivative of fructose, which has been phosphorylated at the 6-hydroxy group. It is one of several possible fructosephosphateFructosephosphates are sugar phosphates based upon fructos ...
, by the enzyme
phosphomannose isomerase Mannose-6 phosphate isomerase (MPI), alternately phosphomannose isomerase (PMI) () is an enzyme which facilitates the interconversion of fructose 6-phosphate (F6P) and mannose-6-phosphate (M6P). Mannose-6-phosphate isomerase may also enable the sy ...
, and then enters the
glycolytic pathway
glycolytic pathway
or is converted to
glucose-6-phosphate Glucose 6-phosphate (G6P, sometimes called the Robison ester) is a glucose sugar phosphorylated at the hydroxy group on carbon 6. This dianion is very common in cell (biology), cells as the majority of glucose entering a cell will become phosphoryl ...
by the
gluconeogenic pathway
gluconeogenic pathway
of
hepatocytes A hepatocyte is a cell of the main parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, tho ...
. Mannose is a dominant monosaccharide in ''N''-linked glycosylation, which is a
post-translational modification Post-translational modification (PTM) refers to the covalent and generally enzyme, enzymatic modification of proteins following protein biosynthesis. Proteins are synthesized by ribosomes translation (biology), translating mRNA into polypeptide c ...
of proteins. It is initiated by the ''en bloc'' transfer on Glc3Man9GlcNAc2 to nascent glycoproteins in the endoplasmic reticulum in a co-translational manner as the protein entered through the transport system. Glucose is
hydrolyzed Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile In chemistry, a nucleop ...

hydrolyzed
on fully folded protein and the mannose moieties are hydrolyzed by ER and Golgi-resident mannosidases. Typically, mature human glycoproteins only contain three mannose residues buried under sequential modification by GlcNAc, galactose, and sialic acid. This is important, as the innate immune system in mammals is geared to recognise exposed mannose residues. This activity is due to the prevalence of mannose residues, in the form of mannans, on the surfaces of yeasts. The human immunodeficiency virus displays considerable amount of mannose residues due to the tight clustering of glycans in its viral spike. These mannose residues are the target for broadly neutralizing antibodies.


Biotechnology

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 is a type of sugar alcohol Sugar alcohols (also called polyhydric alcohols, polyalcohols, alditols or glycitols) are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form ...
. It can also be formed from glucose in the Lobry-de Bruyn-van Ekenstein transformation.


Etymology

The root of both "mannose" and "
mannitol Mannitol is a type of sugar alcohol Sugar alcohols (also called polyhydric alcohols, polyalcohols, alditols or glycitols) are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form ...
" is
manna Manna ( he, מָן ''mān'', ; ar, اَلْمَنُّ; sometimes or archaically spelled mana) is, according to the Bible The Bible (from Koine Greek Koine Greek (, , Greek approximately ;. , , , lit. "Common Greek"), also known as ...

manna
, which the
Bible The Bible (from Koine Greek Koine Greek (, , Greek approximately ;. , , , lit. "Common Greek"), also known as Alexandrian dialect, common Attic, Hellenistic or Biblical Greek, was the koiné language, common supra-regional form of Gree ...

Bible
describes as the food supplied to the Israelites during their journey in the region of
Sinai
Sinai
. Several trees and shrubs can produce a substance called manna, such as the "manna tree" (''
Fraxinus ornus ''Fraxinus ornus'', the manna ash or South European flowering ash, is a species of ''Fraxinus ''Fraxinus'' , English language, English name ash, is a genus of flowering plants in the olive and lilac family, Oleaceae. It contains 45–65 speci ...
'') from whose secretions mannitol was originally isolated.


Uses

Mannose (D-mannose) is used as a nutritional supplement, packaged as "d-mannose", to prevent recurrent urinary tract infections.


Configuration

Mannose differs from glucose by inversion of the C-2 chiral center. Mannose displays a ^4C_1 pucker in the solution ring form. This simple change leads to the drastically different biochemistry of the two hexoses. This change has the same effect on the other
aldohexose In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a ...
s, as well.


Mannose PTS permease

The PEP-dependent sugar transporting phosphotransferase system transports and simultaneously phosphorylates its sugar substrates. Mannose XYZ permease is a member of the family, with this distinct method being used by bacteria for sugar uptake particularly exogenous hexoses in the case of mannose XYZ to release the phosphate esters into the cell cytoplasm in preparation for metabolism primarily through the route of glycolysis. The MANXYZ transporter complex is also involved in infection of ''E. coli'' by bacteriophage lambda, with subunit ManY and ManZ being sufficient for proper lambda phage infection. MANXYZ possesses four domains in three polypeptide chains; ManX, ManY, and ManZ. The ManX subunit forms a homodimer that is localized to the cytoplasmic side of the membrane. ManX contains two domains IIA and IIB linked by a hinge peptide with each domain containing a phosphorylation site and phosphoryl transfer occurs between both subunits. ManX can be membrane bound or not. The ManY and ManNZ subunits are hydrophobic integral membrane proteins with six and one transmembrane alpha helical spanner(s). The phosphoryl group of PEP is transferred to the imported sugar via Enzyme 1, histidine protein phosphate carrier, and then to the ManX, ManY, and ManZ subunits of the ManXYZ transportation complex, which phosphorylates the entering hexose sugar, creating a hexose-6-phosphate.


See also

* α-Mannosidase * Mannose receptor *
Mannan oligosaccharide-based nutritional supplements Glucomannan is a water-soluble polysaccharide , a beta-glucan polysaccharide Image:amylose 3Dprojection.svg">350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. ...
*
Rhamnose Rhamnose (Rha, Rham) is a naturally occurring deoxy sugar Image:Alpha-L-Rhamnopyranose.svg, 150px, rhamnose Deoxy sugars are sugars that have had a hydroxyl group replaced with a hydrogen atom. Examples include: * Deoxyribose, or 2-deoxy-D-rib ...
, 6-deoxy-L-mannose


References

{{Carbohydrates Aldohexoses Articles containing video clips Pyranoses Glycerols