Aspartic acid (or asparaginic acid) plays a vital role in metabolism during the synthesis of other amino acids and metabolites in the citric acid cycle. Among the amino acids that are synthesized from aspartic acid are asparagine, arginine, lysine, methionine, threonine, isoleucine, and several nucleotides. Aspartic acid is also a metabolite in the urea cycle and participates in gluconeogenesis, the generation of glucose from non-sugar carbon substrates. Aspartic acid is alanine with one of the beta-hydrogens replaced by a carboxylic acid group. Measurement of aspartic acid is included in the Amino Acids, Plasma and Amino Acids, Urine tests along with 23 other amino acids.
Aspartic acid (Asp/D) is the carboxylic acid analog of asparagine. As a neurotransmitter, aspartic acid may provide resistance to fatigue and thus lead to greater endurance, although not everyone supports this view. Aspartic acid is a non-essential amino acid that is made from glutamic acid by enzymes that use vitamin B6 as a coenzyme. The biosynthesis of aspartate is facilitated by an aminotransferase that catalyzes the transfer of an amino group from another molecule such as alanine or glutamine and yields aspartic acid and an alpha-keto acid.
Aspartic acid plays an important role in the urea cycle and DNA metabolism. Aspartic acid is an important excitatory neurotransmitter, which is sometimes found elevated in patients with seizures and strokes. It is reduced in patients with depression and in patients with brain atrophy.
Magnesium and zinc may be natural inhibitors of some of the actions of aspartic acid. Aspartic acid, along with the amino acid phenylalanine (and formaldehyde), is part of a new natural sweetener, aspartame. This sweetener is an advance on artificial sweeteners and is probably safe in normal doses in all but patients with phenylketonuria. However, studies on the long-term effects of aspartame on many of the brain's neuropeptides are still lacking.
Aspartic acid may be an important thymus immunostimulant and may protect against some of the harmful effects of radiation. Aspartic acid supplementation is relatively safe while studies are being conducted to clarify its pharmacological and therapeutic roles.
Aspartic acid is found in high concentrations in animal products such as oysters, meat, and meat products (sausages, etc.), and plant products such as grains (mainly sprouts), oats, avocados, asparagus, sugarcane, and sugar beet molasses.