Sialic acid

Sialic acid

Chembox new
ImageFile = Sialic acid.png ImageSize = 185px
IUPACName =
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Section1 = Chembox Identifiers
CASNo = 131-48-6
PubChem = 445063
SMILES =
MeSHName = Sialic+Acid
Section2 = Chembox Properties
Formula = C11H19NO9
MolarMass = 309.273
Appearance = White crystalline powder
Density =
MeltingPt = 186°C (decomposes)
BoilingPt =
Section3 = Chembox Hazards
Solubility =
MainHazards =
FlashPt =
Autoignition =

Sialic acid is a generic term for the "N"- or "O"-substituted derivatives of neuraminic acid, a monosaccharide with a nine-carbon backbone. It is "also" the name for the most common member of this group, N-acetylneuraminic acid (Neu5Ac or NANA). Sialic acids are found widely distributed in animal tissues and in bacteria, especially in glycoproteins and gangliosides. The amino group bears either an acetyl or a glycolyl group. The hydroxyl substituents may vary considerably: acetyl, lactyl, methyl, sulfate, and phosphate groups have been found. [cite journal | author=Schauer R. | title= Achievements and challenges of sialic acid research | journal= Glycoconj. J. | year=2000 | volume=17 | issue=7-9 | pages=485-499 | pmid =11421344]

Sialic acid-rich glycoproteins bind selectin in humans and other organisms. Cancer cells that can metastasize often have a lot of sialic acid-rich glycoproteins. This helps these late-stage cancer cells enter the blood stream.

Sialic acid also plays an important role in Human Influenza infections. The influenza viruses (orthomyxoviridae) have Hemagglutin Activity (HA) glycoproteins on their surface that bind to sialic acids found on the surface of human erythrocytes and on the cell membranes of the upper respiratory tract. This is the basis of heme-agglutination when viruses are mixed with blood cells, and entry of the virus into cells of the upper respiratory tract.

Sialic acid-rich oligosaccharides on the glycoconjugates found on surface membranes help keep water at the surface of cells. The sialic acid-rich regions contribute to creating a negative charge on the cells' surface. Since water is a polar molecule with partial positive charges on both hydrogen atoms, it is attracted to cell surfaces and membranes. This also contributes to cellular fluid uptake.

Sialic acid can "hide" mannose antigens on the surface of host cells or bacteria from mannose-binding lectin. This prevents activation of complement.

The term "sialic acid" (from the Greek "σιαλοσ" ("sialos") 'saliva') was first introduced by Swedish biochemist, Gunnar Blix, in 1952.

ee also

* Sialidosis
* Sialoglycoprotein
* Sialyltransferase
* Orthomyxoviridae

References


=Additional

External links

* [http://www.glycoforum.gr.jp/science/word/evolution/ES-A03E.html Sialic acid in evolution]
* [http://expasy.org/cgi-bin/get-entries?KW=Sialic%20acid Sialic acid] in UniProt knowledgebase


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Look at other dictionaries:

  • sialic acid — si·al·ic acid (.)sī .al ik n any of a group of reducing amido acids that are essentially carbohydrates and are found esp. as components of blood glycoproteins and mucoproteins * * * an amino sugar. Sialic acid is a component of some glycoprotein …   Medical dictionary

  • sialic acid — an amino sugar. Sialic acid is a component of some glycoproteins, gangliosides, and bacterial cell walls …   The new mediacal dictionary

  • sialic acid — sialo rūgštis statusas T sritis chemija apibrėžtis Neuramino rūgšties N darinys. atitikmenys: angl. sialic acid rus. сиаловая кислота …   Chemijos terminų aiškinamasis žodynas

  • Sialic acid-binding Ig-like lectin 12 — Sialic acid binding Ig like lectin 12, also known as SIGLEC12, is a human gene. PBB Summary section title = summary text = Sialic acid binding immunoglobulin like lectins (SIGLECs) are a family of cell surface proteins belonging to the… …   Wikipedia

  • sialic acid — noun Any of a group of amino carbohydrates that are substituted forms of neuraminic acid; they are components of glycoproteins and mucoproteins Syn: acetylneuraminic acid …   Wiktionary

  • sialic acid — See neuraminic acid …   Dictionary of molecular biology

  • sialic acid — noun : any of a group of crystalline reducing amido acids of carbohydrate character that are acyl (as acetyl or glycolyl) derivatives of neuraminic acid and that are found especially as components of various gangliosides, blood glycoproteins and… …   Useful english dictionary

  • sialic acid — noun Etymology: Greek sialon saliva Date: 1952 any of a group of reducing amido acids that are essentially carbohydrates and are found especially as components of blood glycoproteins and mucoproteins …   New Collegiate Dictionary

  • sialic acid — [sʌɪ alɪk] noun Biochemistry a substance present in saliva, consisting of a sugar with amino and ester groups. Origin 1950s: from Gk sialon saliva + ic …   English new terms dictionary

  • sialic acid — Any of a group of simple sugar molecules …   English dictionary of cancer terms

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