Chain: charged (-)
Codons: GAC GAT
Aspartic acid (codons: GAC, GAT) is an α-amino acid that is used in the biosynthesis of proteins, specifically its L-isomer (left-handed). It contains an α-amino group, an α-carboxylic acid group, and an aliphatic carboxyl group side chain. At physiological pH (7.4), the amino group is in the protonated form (−NH₃⁺) and the carboxyl group is in the deprotonated form (−COO−). Similarly, the acidic side chain usually occurs in proteins as the aspartate form (−COO−), making aspartic acid a negatively charged amino acid.
Aspartic acid is one of the 20 amino acids encoded in the standard genetic code and is non-essential in humans, as it can be metabollically synthesized. It is generated from oxaloacetate, a metabolic intermediate in many processes, such as the citric acid cycle. In this process, oxaloacetate is converted to aspartate through transamination. In turn, aspartic acid can be transformed into asparagine though transamidation or arginine through the urea cycle. Since the aspartic acid side chain can form hydrogen bond interactions with the peptide backbone, it is often found near the beginning of alpha-helices or in beta sheets.
In 1827, aspartic acid was first discovered by Auguste-Arthur Plisson and Étienne Ossian Henry by hydrolysis of asparagine, which had been previously isolated from asparagus juice in 1806 by Louis Nicolas Vauquelin and his assistant Pierre Jean Robiquet.
Properties
Side chain: hydrophilic (negatively charged)
Chemical formula: C₄H₇NO₄
Molar mass: 133.10 g/mol
Density: 1.70 g/cm³