Glutamic acid

Glutamic acid is a monoaminodicarboxylic acid, a non-essential amino acid that is a white powder that is poorly soluble in water and poorly soluble in ethanol. Its salts and esters are called glutamates. L-glutamic acid is of considerable physiological importance.

Glutamic acid is found in 2 isomeric forms, L-glutamic acid and D-glutamic acid.

Glutamic acid and biochemical functions: In amino acid synthesis, L-glutamic acid is the NH2 donor in a transamination reaction. This transforms alpha-keto acids into homologous alpha-amino acids. Examples are glutamate oxalacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT). L-glutamic acid binds the ammonia released during protein and amino acid degradation to form glutamine. In the citrate cycle (tricarboxylic acid cycle) L-glutamate is formed from alpha-ketoglutarate.

L-glutamic acid and CNS: L-glutamic acid is one of the most important excitatory neurotransmitters in the central nervous system (CNS). L-glutamate (the term glutamate is used synonymously with glutamic acid in biochemistry) is released presynaptically. Postsynaptically, the substance binds to specific glutamate receptors. In the brain, L-glutamic acid is decarboxylated by L-glutamic acid decarboxylase to gamma-aminobutyric acid (GABA).

Apparently, glutamates also play a role in the development of dementia. In patients with dementia, the glutamate concentration between the nerve cells is continuously elevated. There is, so to speak, a permanent excitation of the nerve cells and a reduction in function.

Glutamic acid as a food additive: L-glutamic acid (E 620) and some of its salts (see E 621 and E 622 - E 625) are used as flavour enhancers, especially in Asian cuisine.

L-glutamic acid in food: The amino acid occurs in most proteins in different molecular formations and is present in all protein-containing foods. Particularly rich in L-glutamic acid (also known as L-glutamate) are cheese, meat and chicken products, walnuts, whole wheat flour, etc.

Glutamic acid in cosmetics (INCI name: glutaminic acid): Glutamic acid is used in cosmetic formulations as moisturizer, antistatic agent and hair conditioning agent.

High doses of glutamic acid have an effect in animal experiments and are neurotoxic in humans. Toxic doses, however, are not reached by normal food intake.

Glutamic acid hypersensitivities are observed in the China Spice Syndrome , which can trigger considerable system reactions in genetically predisposed people depending on the dose.

Disodium glutamate can also trigger acute bronchial asthma and angioedema. Detection is by provocation (increasing oral doses of 0.5 - 5.0g - threshold dose usually between 1.5 and 3.0g).

The reference ranges (normal values) for glutamic acid in blood findings are between 20-107 µmol/ml for infants, between 18-65 µmol/ml for children and between 28-92 µmol/ml for adults.

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