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Asparagine

Asparagine may be abbreviated as "Asn". For other uses of this abbreviation, see ASN (disambiguation).
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L-Asparagine
Skeletal formula of L-asparagine
Ball-and-stick model of the L-asparagine molecule as a zwitterion
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IUPAC name
Asparagine
Other names
2-Amino-3-carbamoylpropanoic acid
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70-47-3 7pxY
ChEBI CHEBI:17196 7pxY
ChEMBL ChEMBL58832 7pxY
ChemSpider 6031 7pxY
DrugBank DB03943 7pxY
EC-number 200-735-9
Jmol-3D images Image
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KEGG C00152 7pxY
PubChem Template:Chembox PubChem/format
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C4H8N2O3
Molar mass Lua error in Module:Math at line 495: attempt to index field 'ParserFunctions' (a nil value). g·mol−1
Appearance white crystals
Density 1.543 g/cm3
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2.94 g/100 mL
Solubility soluble in acid, alkali
negligible in methanol, ethanol, ether, benzene
log P -3.82
Acidity (pKa) 2.02 (carboxyl), 8.80 (amino)[1]
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Crystal structure orthorhomic
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-789.4 kJ/mol
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NFPA 704

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Thermodynamic
data

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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 14pxY verify (what is10pxY/10pxN?)
Infobox references

Asparagine (abbreviated as Asn or N) is one of the 20 most-common natural amino acids on Earth. It has carboxamide as the side-chain's functional group. It is not an essential amino acid. Its codons are AAU and AAC.[2]

A reaction between asparagine and reducing sugars or reactive carbonyls produces acrylamide (acrylic amide) in food when heated to sufficient temperature. These products occur in baked goods such as French fries, potato chips, and toasted bread.

History

Asparagine was first isolated in 1806 in a crystalline form by French chemists Louis Nicolas Vauquelin and Pierre Jean Robiquet (then a young assistant) from asparagus juice,[3][4] in which it is abundant, hence the chosen name. It was the first amino acid to be isolated.

Three years later, in 1809, Pierre Jean Robiquet identified a substance from liquorice root with properties he qualified as very similar to those of asparagine, and that Plisson identified in 1828 as asparagine itself.[5]

Structural function in proteins

Since the asparagine side-chain can form hydrogen bond interactions with the peptide backbone, asparagine residues are often found near the beginning and the end of alpha-helices, and in turn motifs in beta sheets. Its role can be thought as "capping" the hydrogen bond interactions that would otherwise be satisfied by the polypeptide backbone. Glutamines, with an extra methylene group, have more conformational entropy and thus are less useful in this regard.

Asparagine also provides key sites for N-linked glycosylation, modification of the protein chain with the addition of carbohydrate chains. Typically, a carbohydrate tree can solely be added to an asparagine residue if the latter is flanked on the C side by X-serine or X-threonine, where X is any amino acid with the exception of proline.[6]

Sources

Dietary sources

Asparagine is not essential for humans, which means that it can be synthesized from central metabolic pathway intermediates and is not required in the diet.

File:Gemuesespargel Klasse II 2008-05.jpg
Asparagus is a source of L-asparagine.

Asparagine is found in:

Biosynthesis

The precursor to asparagine is oxaloacetate. Oxaloacetate is converted to aspartate using a transaminase enzyme. The enzyme transfers the amino group from glutamate to oxaloacetate producing α-ketoglutarate and aspartate. The enzyme asparagine synthetase produces asparagine, AMP, glutamate, and pyrophosphate from aspartate, glutamine, and ATP. In the asparagine synthetase reaction, ATP is used to activate aspartate, forming β-aspartyl-AMP. Glutamine donates an ammonium group, which reacts with β-aspartyl-AMP to form asparagine and free AMP.

File:Asn biosynthesis.gif
The biosynthesis of asparagine from oxaloacetate

Degradation

Asparagine usually enters the citric acid cycle in humans as malate.[citation needed] In bacteria, the degradation of asparagine leads to the production of oxaloacetate which is the molecule which combines with citrate in the citric acid cycle (Kreb's cycle). Asparagine is hydrolyzed to aspartate by asparaginase. Aspartate then undergoes transamination to form glutamate and oxaloacetate from alpha-ketogluterate.

Function

Asparagine is required for development and function of the brain.[medical citation needed] It also plays an important role in the synthesis of ammonia.

The addition of N-acetylglucosamine to asparagine is performed by oligosaccharyltransferase enzymes in the endoplasmic reticulum.[7] This glycosylation is important both for protein structure[8] and protein function.[9]

Betaine structure

File:Betain-Asparagin.png
(S)-Asparagine (left) and (R)-asparagine (right) in zwitterionic form at neutral pH.

External links

References

  1. ^ R. M. C. Dawson, Daphne Elliott, W. H. Elliott and K. M. Jones. Clarendon, ed. (1959). Data for Biochemical Research. Oxford: Clarendon Press. OCLC 644267041. 
  2. ^ "Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)", Pure Appl. Chem. 56 (5), 1984: 595–624, doi:10.1351/pac198456050595 .
  3. ^ Vauquelin LN, Robiquet PJ (1806). "La découverte d'un nouveau principe végétal dans le suc des asperges". Annales de Chimie 57: 88–93. 
  4. ^ R.H.A. Plimmer (1912) [1908]. R.H.A. Plimmer & F.G. Hopkins, ed. The chemical composition of the proteins. Monographs on biochemistry. Part I. Analysis (2nd ed.). London: Longmans, Green and Co. p. 112. Retrieved January 18, 2010. 
  5. ^ Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D. (1898). "Glycyrrhiza (U. S. P.)—Glycyrrhiza". King's American Dispensatory. Henriette's Herbal Homepage. 
  6. ^ Brooker, Robert; Widmaier, Eric; Graham, Linda; Stiling, Peter; Hasenkampf, Clare; Hunter, Fiona; Bidochka, Michael; Riggs, Daniel (2010). "Chapter 5: Systems Biology of Cell Organization". Biology (Canadian ed.). United States of America: McGraw-Hill Ryerson. pp. 105–106. ISBN 978-0-07-074175-1. 
  7. ^ Burda, Patricie; Aebi, Markus (1999). "The dolichol pathway of N-linked glycosylation". Biochimica et Biophysica Acta (BBA) - General Subjects 1426 (2): 239. doi:10.1016/S0304-4165(98)00127-5. 
  8. ^ Imperiali, Barbara; o’Connor, Sarah E (1999). "Effect of N-linked glycosylation on glycopeptide and glycoprotein structure". Current Opinion in Chemical Biology 3 (6): 643. PMID 10600722. doi:10.1016/S1367-5931(99)00021-6. 
  9. ^ Patterson, Marc C. (2005). "Metabolic Mimics: The Disorders of N-Linked Glycosylation". Seminars in Pediatric Neurology 12 (3): 144–51. PMID 16584073. doi:10.1016/j.spen.2005.10.002.