Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

that is used in the biosynthesis of proteins. Like all other amino acids, it contains an amino group and a carboxylic acid. Its α-amino group is in the protonated –NH form under physiological conditions, while its α-carboxylic acid group is deprotonated −COO⁻ under physiological conditions. Aspartic acid has an acidic side chain (CH₂COOH) which reacts with other amino acids, enzymes and proteins in the body. Under physiological conditions (pH 7.4) in proteins the side chain usually occurs as the negatively charged aspartate form, −COO⁻. It is a non-

essential amino acid An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life form ...

in humans, meaning the body can synthesize it as needed. 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 GAU and GAC. D-Aspartate is one of two D-amino acids commonly found in mammals. /sup> In proteins aspartate sidechains are often hydrogen bonded to form asx turns or

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 b ...

s, which frequently occur at the N-termini of

alpha helices The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues ear ...

. The L-isomer of Asp is one of the 22

proteinogenic amino acid Proteinogenic amino acids are amino acids that are incorporated biosynthetically into proteins during translation. The word "proteinogenic" means "protein creating". Throughout known life, there are 22 genetically encoded (proteinogenic) amino aci ...

s, i.e., the building blocks of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s. Aspartic acid, like glutamic acid, is classified as an acidic amino acid, with a pK_a of 3.9, however in a peptide this is highly dependent on the local environment, and could be as high as 14. Asp is pervasive in biosynthesis.

Discovery

Aspartic acid was first discovered in 1827 by Auguste-Arthur Plisson and

Étienne Ossian Henry Étienne-Ossian Henry (27 November 1798 in Paris – 26 August 1873) was a French chemist, son of Nöel Étienne Henry (1769–1832), and trained by his father, who was director of the Central Pharmacy of the Parisian hospitals and professor ...

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...

asparagine Asparagine (symbol Asn or N) is an α-amino acid 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 depro ...

, which had been isolated from

asparagus Asparagus, or garden asparagus, folk name sparrow grass, scientific name ''Asparagus officinalis'', is a perennial flowering plant species in the genus '' Asparagus''. Its young shoots are used as a spring vegetable. It was once classified in ...

juice in 1806. Their original method used lead hydroxide, but various other acids or bases are now more commonly used instead.

Forms and nomenclature

There are two forms or enantiomers of aspartic acid. The name "aspartic acid" can refer to either enantiomer or a mixture of two.. Of these two forms, only one, "L-aspartic acid", is directly incorporated into proteins. The biological roles of its counterpart, "D-aspartic acid" are more limited. Where enzymatic synthesis will produce one or the other, most chemical syntheses will produce both forms, "DL-aspartic acid", known as a racemic mixture.

Synthesis

Biosynthesis

In the human body, aspartate is most frequently synthesized through the

transamination Transamination is a chemical reaction that transfers an amino group to a ketoacid to form new amino acids. This pathway is responsible for the deamination of most amino acids. This is one of the major degradation pathways which convert essential ...

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 ...

. The biosynthesis of aspartate is facilitated by an

aminotransferase 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 co ...

enzyme: the transfer of an

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...

group from another molecule such as alanine or glutamine yields aspartate and an alpha-keto acid.

Chemical synthesis

Industrially, aspartate is produced by amination of fumarate catalyzed by L- aspartate ammonia-lyase.

Racemic In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...

aspartic acid can be synthesized from diethyl sodium phthalimidomalonate, (C₆H₄(CO)₂NC(CO₂Et)₂).

Metabolism

In plants and

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s, aspartate is the precursor to several amino acids, including four that are essential for humans: methionine, threonine, isoleucine, and lysine. The conversion of aspartate to these other amino acids begins with reduction of aspartate to its "semialdehyde", O₂CCH(NH₂)CH₂CHO.

Asparagine Asparagine (symbol Asn or N) is an α-amino acid 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 depro ...

is derived from aspartate via transamidation: :-O₂CCH(NH₂)CH₂CO₂- + ''G''C(O)NH₃+ O₂CCH(NH₂)CH₂CONH₃+ + ''G''C(O)O (where ''G''C(O)NH₂ and ''G''C(O)OH are

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 glutamic acid, respectively)

Other biochemical roles

Aspartate has many other biochemical roles. It is a metabolite in the

urea cycle The urea cycle (also known as the ornithine cycle) is a cycle of Biochemistry, biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). Animals that use this cycle, mainly amphibians and mammals, are called ureotelic. The urea cycle ...

and participates in gluconeogenesis. It carries reducing equivalents in the malate-aspartate shuttle, which utilizes the ready interconversion of aspartate and

, which is the oxidized (dehydrogenated) derivative of

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 ( ...

. Aspartate donates one nitrogen atom in the biosynthesis of

inosine Inosine is a nucleoside that is formed when hypoxanthine is attached to a ribose ring (also known as a ribofuranose) via a β-N9- glycosidic bond. It was discovered in 1965 in analysis of RNA transferase. Inosine is commonly found in tRNAs and is ...

, the precursor to the

purine Purine is a heterocyclic aromatic organic compound that consists of two rings ( pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines ...

bases. In addition, aspartic acid acts as a hydrogen acceptor in a chain of ATP synthase. Dietary L-aspartic acid has been shown to act as an inhibitor of Beta-glucuronidase, which serves to regulate

enterohepatic circulation Enterohepatic circulation refers to the circulation of biliary acids, bilirubin, drugs or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte and transport back to the liver. Ent ...

of bilirubin and bile acids.

Interactive pathway map

Neurotransmitter

Aspartate (the

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

of aspartic acid) stimulates NMDA receptors, though not as strongly as the amino acid neurotransmitter L-glutamate does.

Applications & market

In 2014, the global market for aspartic acid was or about $117 million annually with potential areas of growth accounting for an of $8.78 billion (Bn).Transparency Market Research. Superabsorbent polymers market - global industry analysis, size, share, growth, trends and forecase, 2014-2020. (2014). The three largest market segments include the U.S., Western Europe, and China. Current applications include biodegradable polymers ( polyaspartic acid), low calorie sweeteners ( aspartame), scale and corrosion inhibitors, and resins.

Superabsorbent polymers

One area of aspartic acid market growth is biodegradable

superabsorbent polymer A superabsorbent polymer (SAP) (also called slush powder) is a water-absorbing hydrophilic homopolymers or copolymers that can absorb and retain extremely large amounts of a liquid relative to its own mass. Water-absorbing polymers, which are cla ...

s (SAP), and hydrogels. The superabsorbent polymers market is anticipated to grow at a

compound annual growth rate Compound annual growth rate (CAGR) is a business and investing specific term for the geometric progression ratio that provides a constant rate of return over the time period. CAGR is not an accounting term, but it is often used to describe some ele ...

of 5.5% from 2014 to 2019 to reach a value of $8.78Bn globally. Around 75% of superabsorbent polymers are used in disposable diapers and an additional 20% is used for adult incontinence and

feminine hygiene Feminine hygiene products are personal care products used during menstruation, vaginal discharge, and other bodily functions related to the vulva and vagina. Products that are used during menstruation may also be called menstrual hygiene product ...

products. Polyaspartic acid, the polymerization product of aspartic acid, is a biodegradable substitute to

polyacrylate An acrylate polymer (also known as acrylic or polyacrylate) is any of a group of polymers prepared from acrylate monomers. These plastics are noted for their transparency, resistance to breakage, and elasticity. Acrylate polymer is commonly used ...

. The polyaspartate market comprises a small fraction (est. < 1%) of the total SAP market.

Additional uses

In addition to SAP, aspartic acid has applications in the $19Bn fertilizer industry, where polyaspartate improves water retention and nitrogen uptake; the $1.1Bn (2020) concrete floor coatings market, where polyaspartic is a low VOC, low energy alternative to traditional epoxy resins; and lastly the >$5Bn scale and corrosion inhibitors market.

Sources

Dietary sources

Aspartic acid is not an

, which means that it can be synthesized from central metabolic pathway intermediates in humans, and does not need to be present in the diet. In

eukaryotic Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...

cells, roughly 1 in 20 amino acids incorporated into a protein is an aspartic acid, and accordingly almost any source of dietary protein will include aspartic acid. Additionally, aspartic acid is found in: * Dietary supplements, either as aspartic acid itself or

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively c ...

(such as magnesium aspartate) * The sweetener aspartame, which is made from an aspartic acid and phenylalanine

References

External links

GMD MS Spectrum
* {{Authority control Proteinogenic amino acids Glucogenic amino acids Acidic amino acids Dicarboxylic acids Excitatory amino acids Urea cycle NMDA receptor agonists