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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 am ...
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
codon The genetic code is the 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 p ...
s 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 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 group ...
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 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 ea ...
. 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 ac ...
s, i.e., the building blocks of proteins. Aspartic acid, like
glutamic acid Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) 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 syn ...
, is classified as an acidic amino acid, with a pKa 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 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 Nöel Étienne Henry (1769–1832), and trained by his father, who was director of the Central Pharmacy of the Parisian hospitals and professor ...
by hydrolysis of
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 juice in 1806. Their original method used
lead hydroxide Lead hydroxide may refer to: * Lead(II) hydroxide * Lead(IV) hydroxide {{Short pages monitor