Biochemistry

See Also

Description

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.

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 primarilly in baked goods such as french fries, potato chips, and roasted coffee.

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 smell observed in the urine of some individuals after their consumption of asparagus is attributed to a byproduct of the metabolic breakdown of asparagine, asparagine-amino-succinic-acid monoamide. (However, some scientists disagree and implicate other substances in the smell, especially methanethiol).

Biosynthesis

Asparagine is a nonessential amino acid, meaning that it can be synthesized from central metabolic pathyway intermediates in humans. 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

Nervous system needs Asparagine to maintain the equilibrium and also in amino acid transformation. It also plays an important role in the synthesis of ammonia.

Sources

Dairy products, beef, poultry, meat and eggs

Links

• Asparagine
• Properties of asparagine synthetase in asparagine-independent variants of Jensen rat sarcoma cells induced by 5-azacytidine.
• NCBI entry Asparagine synthetase (Asns)
• MetaCyc Pathway: asparagine biosynthesis I (includes links to pathways II and III)

Attribution

• This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Asparagine".