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 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. The L-isomer of aspartic acid is one of the 22

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

s, i.e., the building blocks of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s. D-aspartic acid is one of two D-amino acids commonly found in mammals. Apart from a few rare exceptions, D-aspartic acid is not used for protein synthesis but is incorporated into some

peptides Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Dalton (unit), Da or more are called proteins. Chains of fewer t ...

and plays a role as a

neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotra ...

neuromodulator Neuromodulation is the physiological process by which a given neuron uses one or more chemicals to regulate diverse populations of neurons. Neuromodulators typically bind to metabotropic, G-protein coupled receptors (GPCRs) to initiate a secon ...

. Like all other amino acids, aspartic acid 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 forms ...

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

codon 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 prote ...

s GAU and GAC. In proteins aspartate sidechains are often hydrogen bonded to form

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 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 ...

s, which frequently occur at the N-termini 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 ...

. Aspartic acid, like

glutamic acid 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 non-essential nutrient for humans, meaning that the human body can ...

, 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. The one-letter code D for aspartate was assigned arbitrarily, with the proposed mnemonic aspar''D''ic acid.

Discovery

Aspartic acid was first discovered in 1827 by

Auguste-Arthur Plisson Auguste-Arthur Plisson (died August 1832) was a French chemist. Born in Orléans, Plisson was orphaned at an early age, but overcame the difficulties that caused him with the determination he brought to being a student of chemistry in Paris. Taught ...

and

Étienne-Ossian Henry Étienne-Ossian Henry (27 November 1798 in Paris – 26 August 1873) was a French chemist, son of Noël-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 reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

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 (''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 1806. Their original method used

lead hydroxide Lead hydroxide may refer to: * Lead(II) hydroxide * {{Short pages monitor