Aspartic acid

Aspartic acid is a protein-building amino acid with a negatively charged carboxylate side chain at physiological pH. It also participates in metabolism and acts as an excitatory neurotransmitter in some nervous systems.

Amino acid: An organic molecule with amino and carboxyl functional groups; amino acids are the building blocks of proteins. Aspartic acid is one member of this protein-building molecular family.
Aspartate aminotransferase: An enzyme that reversibly transfers an amino group between aspartate and alpha-ketoglutarate, producing oxaloacetate and glutamate. It interconverts aspartate with a central metabolic intermediate.
Aspartame: An artificial sweetener made from aspartic acid and phenylalanine joined as a methyl ester. Aspartic acid is one of the two amino-acid components of this sweetener.
Glutamic acid: A protein-building amino acid with an acidic side chain one methylene group longer than aspartic acid’s. It shares aspartic acid’s charge and many chemical roles but has a longer side chain.
Carboxylic acid: An organic compound containing a carboxyl group, which can donate a proton. Aspartic acid’s side chain contains a carboxyl group that gives it acidic behavior.
Malate-aspartate shuttle: A mitochondrial transport system that transfers reducing equivalents from cytosolic NADH into the mitochondrial matrix. Aspartate carries carbon and amino groups through this shuttle’s exchange cycle.
Aspartate aminotransferase test: A blood test that measures the enzyme aspartate aminotransferase as an indicator of tissue injury. The measured enzyme acts directly on aspartate, though the test does not measure aspartic acid itself.
Asparagine: A protein-building amino acid whose side-chain amide is the neutral counterpart of aspartic acid’s carboxyl group. Replacing aspartic acid’s side-chain carboxylate with an amide removes its acidic charge.
Aspartate: The deprotonated form of aspartic acid, carrying a negative charge on its side-chain carboxylate. At physiological pH, aspartic acid is predominantly present in this ionized form.
Urea cycle: A series of reactions in the liver that converts toxic ammonia into urea for excretion. Aspartate supplies one of the two nitrogen atoms in urea.

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