aspartic

Aspartic acid, also called aspartate in its deprotonated form, is one of the 20 standard amino acids used to build proteins. It is a polar, acidic amino acid with the chemical formula C4H7NO4 and contains two carboxyl groups and one amino group. It is encoded by the genetic code with the codons GAU and GAC.

At physiological pH, aspartic acid bears a negative charge because both the α-carboxyl group and the side-chain carboxyl group are deprotonated, while the amino group is typically protonated. This gives the molecule an overall net charge of −1 under normal cellular conditions.

Biological roles: Aspartate residues contribute to protein structure and function, including enzyme active sites. It participates in nitrogen metabolism as an amino donor in transamination reactions, notably forming oxaloacetate from α-ketoglutarate via aspartate aminotransferase. It provides nitrogen for the urea cycle and for nucleotide biosynthesis, contributing to purine and pyrimidine formation. Aspartate is also a precursor to other amino acids, such as asparagine, methionine, threonine, and lysine. In the brain, N-acetylaspartate is a major metabolite derived from aspartate and serves as a neuronal marker in imaging.

Source and metabolism: Aspartate is obtained from dietary proteins and is synthesized endogenously through transamination. It can interconvert with oxaloacetate and participate in the citric acid cycle, linking amino acid and energy metabolism.

Dietary and therapeutic notes: In foods, aspartic acid is a common component of proteins and is generally regarded as safe. D-aspartic acid is marketed as a dietary supplement with claimed hormonal effects, though evidence is mixed and recommendations vary.