Asparagine

Asparagine
Systematic (IUPAC) name
(2S)-2-amino-3-carbamoyl-propanoic acid
Identifiers
CAS number	70-47-3
PubChem	236
Chemical data
Formula	C4H8N2O3
Mol. weight	132.118
SMILES	N[C@@H](CC(N)=O)C(O)=O
Complete data

For other articles using the abbreviation or acronym asn see ASN.

Asparagine is one of the 20 most common natural amino acids on Earth. It has carboxamide as the side chain's functional group. It is considered a non-essential amino acid.

note: Aspartic acid, also called asparaginic acid and alpha-aminosuccinic acid is an acidic, α-amino acid that is found in many proteins, is common in young sugar cane and sugar beets, and is closely related to the amino acid asparagine. Along with glutamic acid, it is classified as an acidic amino acid.

In humans, the L-isomer, which is the only form that is involved in protein synthesis, is one of the 20 standard amino acids required for normal functioning. However, it is considered to be non-essential since it does not have to be taken in with the diet, but can be synthesized by the human body from other compounds through chemical reactions.

Aspartic acid's three letter code is ASP, its one letter code is D, its codons are GAU and GAC, and its systematic name is 2-Aminobutanedioic acid (IUPAC-IUB 1983).

Asparagine Asnd N d 2-Amino-3-carbamoylpropanoic acid H2N-CO-CH2-CH(NH2)-COOH

Its three-letter abbreviation is Asn, and its one-letter abbreviation is N. A three-letter designation for either asparagine or aspartic acid is Asx (one-letter abbreviation: B).

A reaction between asparagine and reducing sugars or reactive carbonyls produces acrylamide (acrylic amide) in food when heated to sufficient temperature, i.e. baking. These occur primarily in baked goods such as french fries, potato chips, and roasted coffee.

Structure

In biochemistry, the term amino acid is frequently used to refer specifically to alpha amino acids: those amino acids in which the amino and carboxylate groups are attached to the same carbon, the so-called α–carbon (alpha carbon). The general structure of these alpha amino acids is:

     R
     |
 H2N-C-COOH
     |
     H

where R represents a side chain specific to each amino acid.

Most amino acids occur in two possible optical isomers, called D and L. The L amino acids represent the vast majority of amino acids found in proteins. They are called proteinogenic amino acids. As the name "proteinogenic" (literally, protein building) suggests, these amino acid are encoded by the standard genetic code and participate in the process of protein synthesis. In aspartic acid, only the L-stereoisomer is involved in protein synthesis.

Aspartic acids chemical formula is

History

Asparagine was first isolated in 1806 from asparagus juice, in which it is abundant — hence its name — becoming the first amino acid to be isolated. The characteristic smell observed in the urine of individuals after their consumption of asparagus is attributed to various metabolic byproducts of asparagine: in 1891, Marceli Nencki claimed that the substance responsible was methanethiol, and Robert White's 1975 research indicated that the substances were various thioesters. Other likely possibilities include asparagine aminosuccinic monoamide. Allison and McWhirter's 1956 research indicated that some individuals do not produce this odor after asparagus consumption, and that this is autosomal; however, a re-examination in 1980 showed that these individuals are, rather, not able to detect the odor.

Structural function in proteins

Since the asparagine side chain can make efficient hydrogen bond interactions with the peptide backbone, asparagines are often found near the beginning and end of alpha-helices, and in turn motifs in beta sheets. Its role can be thought as "capping" the hydrogen bond interactions which would otherwise need to be satisfied by the polypeptide backbone. Glutamines have 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.

Biosynthesis

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

The biosynthesis of asparagine from oxaloacetate

Degradation

Aspartate is a glucogenic amino acid. L-asparginase hydrolyzes the amide group to form aspartate and ammonium. A transaminase converts the aspartate to oxaloacetate which can then be metabolized in the citric acid cycle or gluconeogenesis.

Function

The nervous system needs asparagine to maintain the equilibrium, as well as in amino acid transformation. It also plays an important role in the synthesis of ammonia.

Sources

Asparagus, dairy products, potatoes, beef, poultry, meat, and eggs.

References

ISBN links support NWE through referral fees

• Doolittle, R. F. 1989. Redundancies in protein sequences. In G. D. Fasman, ed., Prediction of Protein Structures and the Principles of Protein Conformation. New York: Plenum Press. ISBN 0306431319.

• International Union of Pure and Applied Chemistry and International Union of Biochemistry and Molecular Biology (IUPAC-IUB) Joint Commission on Biochemical Nomenclature. 1983. Nomenclature and symbolism for amino acids and peptides: Recommendations on organic & biochemical nomenclature, symbols & terminology. IUPAC-IUB. Retrieved June 14, 2007.
• Lehninger, A. L., D. L. Nelson, and M. M. Cox. 2000. Lehninger Principles of Biochemistry, 3rd ed. New York: Worth Publishing. ISBN 1572591536.

External links

• Computational Chemistry Wiki
• Asparagus Makes Your Pee Stink

Template:ChemicalSources

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