Aspartic acid

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. Similar to all other amino acids it contains an amino group and a carboxylic acid. Its α-amino group is in the protonated –NH+3 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 in humans, meaning the body can synthesize it as needed. It is encoded by all the codons GAU and GAC. 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. Similar to all other amino acids it contains an amino group and a carboxylic acid. Its α-amino group is in the protonated –NH+3 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 in humans, meaning the body can synthesize it as needed. It is encoded by all the codons GAU and GAC. D-Aspartate is one of two D-amino acids commonly found in mammals. In proteins aspartate sidechains are often hydrogen bonded to form asx turns or asx motifs, which frequently occur at the N-termini of alpha helices. The L-isomer of Asp is one of the 22 proteinogenic amino acids, i.e., the building blocks of proteins. Aspartic acid, like glutamic acid, 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. Because aspartate can be synthesized by the body it is classified as a non-essential amino acid. Aspartic acid was first discovered in 1827 by Auguste-Arthur Plisson and Étienne Ossian Henry by hydrolysis of asparagine, which had been isolated from asparagus juice in 1806. Their original method used lead hydroxide, but various other acids or bases are more commonly used instead. 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. In the human body, aspartate is most frequently synthesized through the transamination of oxaloacetate. The biosynthesis of aspartate is facilitated by an aminotransferase enzyme: the transfer of an amine group from another molecule such as alanine or glutamine yields aspartate and an alpha-keto acid. Aspartate also plays an important role in the urea cycle. Industrially, aspartate is produced by amination of fumarate catalyzed by L-aspartate ammonia-lyase.