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 not an essential
amino acid. Its codons are AAU and AAC. A reaction between asparagine and
reducing sugars or other source of carbonyls produces acrylamide 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 from asparagus juice, 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.
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.
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. Asparagine is found in:
Animal sources: dairy, whey, beef, poultry, eggs, fish, lactalbumin,
seafood Plant sources: asparagus, potatoes,
legumes, nuts, seeds, soy, whole grains = 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. Degradation
Asparagine usually enters the citric acid cycle in humans as malate. 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.
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. 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. This glycosylation is important both for
protein structure and protein function. Betaine structure
External links GMD MS Spectrum
Why Asparagus Makes Your Pee Stink References