L-asparagine
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Asparagine (symbol Asn or N) is an α-
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain
carboxamide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent any group, typically organyl groups or hydrogen atoms. The amide group is called a pe ...
, classifying it as a polar (at physiological pH),
aliphatic In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated (in which all ...
amino acid. It is non-essential in humans, meaning the body can synthesize it. It is
encoded In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...
by the
codons Genetic code is a set of rules used by living cells to translate information encoded within genetic material ( DNA or RNA sequences of nucleotide triplets or codons) into proteins. Translation is accomplished by the ribosome, which links pro ...
AAU and AAC. The one-letter symbol N for asparagine was assigned arbitrarily, with the proposed mnemonic asparagi''N''e;


History

Asparagine was first isolated in 1806 in a crystalline form by French chemists
Louis Nicolas Vauquelin Louis Nicolas Vauquelin FRS(For) HFRSE (; 16 May 1763 – 14 November 1829) was a French pharmacist and chemist. He was the discoverer of chromium and beryllium. Early life Vauquelin was born at Saint-André-d'Hébertot in Normandy, France, th ...
and
Pierre Jean Robiquet Pierre Jean Robiquet (; 13 January 1780 – 29 April 1840) was a French chemist. He laid founding work in identifying amino acids, the fundamental building blocks of proteins. He did this through recognizing the first of them, asparagine, in 18 ...
(then a young assistant). It was isolated from
asparagus Asparagus (''Asparagus officinalis'') is a perennial flowering plant species in the genus ''Asparagus (genus), Asparagus'' native to Eurasia. Widely cultivated as a vegetable crop, its young shoots are used as a spring vegetable. Description ...
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 Liquorice (Commonwealth English) or licorice (American English; see spelling differences; ) is the common name of ''Glycyrrhiza glabra'', a flowering plant of the bean family Fabaceae, from the root of which a sweet, aromatic flavouring is ...
with properties which he qualified as very similar to those of asparagine, and which Plisson identified in 1828 as asparagine itself. The determination of asparagine's structure required decades of research. The
empirical formula In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, is simply SO, as is the empir ...
for asparagine was first determined in 1833 by the French chemists Antoine François Boutron Charlard and
Théophile-Jules Pelouze Théophile-Jules Pelouze (also known as Jules Pelouze), ; 26 February 180731 May 1867) was a French chemist. Life He was born at Valognes, and died in Paris. His father, Edmond Pelouze, was an industrial chemist and the author of several tech ...
; in the same year, the German chemist
Justus Liebig Justus ''Freiherr'' von Liebig (12 May 1803 – 18 April 1873) was a German scientist who made major contributions to the theory, practice, and pedagogy of chemistry, as well as to agricultural and biological chemistry; he is considered one of ...
provided a more accurate formula. In 1846 the Italian chemist
Raffaele Piria Raffaele Piria (Scilla 20 August 1814 – Turin 18 July 1865) was an Italian chemist from Scilla, who lived in Palmi. He converted the substance Salicin into a sugar and a second component, which on oxidation becomes salicylic acid, a major com ...
treated asparagine with
nitrous acid Nitrous acid (molecular formula ) is a weak and monoprotic acid known only in solution, in the gas phase, and in the form of nitrite () salts. It was discovered by Carl Wilhelm Scheele, who called it " phlogisticated acid of niter". Nitrous ac ...
, which removed the molecule's
amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
(–NH2) groups and transformed asparagine into
malic acid Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms ( ...
. This revealed the molecule's fundamental structure: a chain of four carbon atoms. Piria thought that asparagine was a diamide of malic acid; however, in 1862 the German chemist
Hermann Kolbe Adolph Wilhelm Hermann Kolbe (27 September 1818 – 25 November 1884) was a German chemist and academic, and a major contributor to the birth of modern organic chemistry. He was a professor at Marburg and Leipzig. Kolbe was the first to apply t ...
showed that this surmise was wrong; instead, Kolbe concluded that asparagine was an
amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...
of an amine of
succinic acid Succinic acid () is a dicarboxylic acid with the chemical formula (CH2)2(CO2H)2. In living organisms, succinic acid takes the form of an anion, succinate, which has multiple biological roles as a metabolic intermediate being converted into fum ...
. In 1886, the Italian chemist Arnaldo Piutti (1857–1928) discovered a mirror image or "
enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...
" of the natural form of asparagine, which shared many of asparagine's properties, but which also differed from it. Since the structure of asparagine was still not fully known – the location of the amine group within the molecule was still not settled – Piutti synthesized asparagine and thus published its true structure in 1888.


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 of
alpha-helices An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix). The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of l ...
as
asx turn The Asx turn is a structural feature in proteins and polypeptides. It consists of three amino acid residues (labeled i, i+1 and i+2) in which residue i is an aspartate (Asp) or asparagine (Asn) that forms a hydrogen bond from its sidechain CO grou ...
s and
asx motif The Asx motif is a commonly occurring feature in proteins and polypeptides. It consists of four or five amino acid residues with either aspartate or asparagine as the first residue (residue i). It is defined by two internal hydrogen bonds. One is ...
s, and in similar turn motifs, or as amide rings, in
beta sheet The beta sheet (β-sheet, also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a gene ...
s. Its role can be thought as "capping" the hydrogen bond interactions that would otherwise be satisfied by the polypeptide backbone. Asparagine also provides key sites for
N-linked glycosylation ''N''-linked glycosylation is the attachment of an oligosaccharide, a carbohydrate consisting of several sugar molecules, sometimes also referred to as glycan, to a nitrogen atom (the amide nitrogen of an asparagine (Asn) residue of a protein), i ...
, modification of the protein chain with the addition of
carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...
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 Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...
or X-
threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form when dissolved in water), a carboxyl group (which is in the deprotonated −COO− ...
, where X is any amino acid with the exception of
proline Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the p ...
. Asparagine can be hydroxylated in the HIF1 hypoxia-inducible transcription factor. This modification inhibits HIF1-mediated gene activation.


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 A dairy is a place where milk is stored and where butter, cheese, and other dairy products are made, or a place where those products are sold. It may be a room, a building, or a larger establishment. In the United States, the word may also des ...
,
whey Whey is the liquid remaining after milk has been curdled and strained. It is a byproduct of the manufacturing of cheese or casein and has several commercial uses. Sweet whey is a byproduct resulting from the manufacture of rennet types of hard c ...
,
beef Beef is the culinary name for meat from cattle (''Bos taurus''). Beef can be prepared in various ways; Cut of beef, cuts are often used for steak, which can be cooked to varying degrees of doneness, while trimmings are often Ground beef, grou ...
,
poultry Poultry () are domesticated birds kept by humans for the purpose of harvesting animal products such as meat, Eggs as food, eggs or feathers. The practice of animal husbandry, raising poultry is known as poultry farming. These birds are most typ ...
,
eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...
,
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
,
lactalbumin Lactalbumin, also known as "whey protein", is the albumin contained in milk and obtained from whey. Lactalbumin is found in the milk of many mammals. There are alpha Alpha (uppercase , lowercase ) is the first letter of the Greek alphabet ...
,
seafood Seafood is any form of Marine life, sea life regarded as food by humans, prominently including Fish as food, fish and shellfish. Shellfish include various species of Mollusca, molluscs (e.g., bivalve molluscs such as clams, oysters, and mussel ...
* Plant sources: seaweed (spirulina),
potatoes The potato () is a starchy tuberous vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are underground stem tubers of the plant ''Solanum tuberosum'', a perennial in the nightshade famil ...
, soy protein isolate,
tofu or bean curd is a food prepared by Coagulation (milk), coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness: ''silken'', ''soft'', ''firm'', and ''extra (or super) firm''. It originated in Chin ...


Biosynthesis and catabolism

The precursor to asparagine is
oxaloacetate Oxaloacetic acid (also known as oxalacetic acid or OAA) is a crystalline organic compound with the chemical formula HO2CC(O)CH2CO2H. Oxaloacetic acid, in the form of its conjugate base oxaloacetate, is a metabolic intermediate in many processes ...
, which a
transaminase Transaminases or aminotransferases are enzymes that catalyze a transamination reaction between an amino acid and an α-keto acid. They are important in the synthesis of amino acids, which form proteins. Function and mechanism An amino acid con ...
enzyme converts to
aspartate Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. The L-isomer of aspartic acid is one of the 22 proteinogenic amino acids, i.e., the building blocks of protein ...
. The enzyme transfers the amino group from
glutamate Glutamic acid (symbol Glu or E; known as glutamate in its anionic form) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a Essential amino acid, non-essential nutrient for humans, meaning that ...
to oxaloacetate producing α-ketoglutarate and aspartate. The enzyme
asparagine synthetase Asparagine synthetase (or aspartate-ammonia ligase) is a chiefly cytoplasmic enzyme that generates asparagine from aspartate. This amidation reaction is similar to that promoted by glutamine synthetase. The enzyme is ubiquitous in its distributio ...
produces asparagine, AMP, glutamate, and
pyrophosphate In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate () and tetrasodium pyrophosphate (), among others. Often pyrophosphates a ...
from aspartate,
glutamine Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral ...
, and ATP. Asparagine synthetase uses ATP to activate aspartate, forming β-aspartyl-AMP.
Glutamine Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral ...
donates an ammonium group, which reacts with β-aspartyl-AMP to form asparagine and free AMP. In reaction that is the reverse of its biosynthesis, asparagine is hydrolyzed to aspartate by
asparaginase Asparaginase is an enzyme that is used as a medication and in food manufacturing. As a medication, L-asparaginase is used to treat acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LBL). It is given by intravenous, injection into ...
. Aspartate then undergoes transamination to form glutamate and oxaloacetate from alpha-ketoglutarate. Oxaloacetate, which enters the
citric acid cycle The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle, or TCA cycle (tricarboxylic acid cycle)—is a series of chemical reaction, biochemical reactions that release the energy stored in nutrients through acetyl-Co ...
(Krebs cycle).


Acrylamide controversy

Heating a mixture of asparagine and
reducing sugar A reducing sugar is any sugar that is capable of acting as a reducing agent. In an alkaline solution, a reducing sugar forms some aldehyde or ketone, which allows it to act as a reducing agent, for example in Benedict's reagent. In such a react ...
s or other source of
carbonyl In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double bond, double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such a ...
s produces
acrylamide Acrylamide (or acrylic amide) is an organic compound with the chemical formula CH2=CHC(O)NH2. It is a white odorless solid, soluble in water and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary ...
in food. These products occur in baked goods such as French fries, potato chips, and toasted bread. Acrylamide is converted in the liver to glycidamide, which is a possible carcinogen.


Function

Asparagine synthetase is required for normal development of the brain. Asparagine is also involved in
protein synthesis Protein biosynthesis, or protein synthesis, is a core biological process, occurring inside cells, balancing the loss of cellular proteins (via degradation or export) through the production of new proteins. Proteins perform a number of critica ...
during replication of
poxviruses ''Poxviridae'' is a family of double-stranded DNA viruses. Vertebrates and arthropods serve as natural hosts. The family contains 22 genera that are assigned to two subfamilies: ''Chordopoxvirinae'' and ''Entomopoxvirinae''. ''Entomopoxvirinae'' ...
. The addition of ''N''-acetylglucosamine to asparagine is performed by
oligosaccharyltransferase Oligosaccharyltransferase or OST () is a membrane protein complex that transfers a 14-sugar oligosaccharide from dolichol to nascent protein. It is a type of glycosyltransferase. The sugar Glc3Man9GlcNAc2 (where Glc=Glucose, Man= Mannose, and ...
enzymes in the
endoplasmic reticulum The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryote, eukaryotic cell, and has many other important functions such as protein folding. The word endoplasmic means "within the cytoplasm", and reticulum is Latin for ...
. This glycosylation is involved in protein structure and function.


See also

* Potassium asparaginate


References


External links


GMD MS Spectrum
{{Authority control Proteinogenic amino acids Glucogenic amino acids Carboxamides Alpha-Amino acids