Glutamic acid

Glutamic acid or, in its ionized form, glutamate (abbreviated Glu or E) is one of the twenty amino acids that make up proteins. Glutamic acid exists in three optically isomeric forms and is generally found as both the free and bound L-dextrorotatory form in glutamine and many proteins in plants and animals, which is generally obtained by hydrolysis of gluten or from wastewater from the manufacture of gluten. beet sugar or by fermentation. Glutamic acid is critical for cell function and is not an essential nutrient because humans can synthesize it from other compounds. It belongs to the group of so-called acidic amino acids, or with a negative charge at physiological pH, because it has a second carboxyl group in its secondary chain. Its pK are 1.9, 3.1, 10.5 for its alpha-carboxyl, gamma-carboxyl, and alpha-amino groups.

It is the excitatory neurotransmitter par excellence of the human cerebral cortex. Its role as a neurotransmitter is mediated by the stimulation of specific receptors, called glutamate receptors, which are classified as: ionotropic (ion channels) and metabotropic receptors (with seven transmembrane domains and coupled to G proteins) of glutamic acid.

All neurons contain glutamate, but only a few use it as a neurotransmitter. It is potentially excitotoxic, so there is a complex machinery so that the levels of this substance are always regulated.

It plays a central role in relation to transamination processes and in the synthesis of different amino acids that require the prior formation of this acid, such as proline, hydroxyproline, ornithine and arginine. It accumulates in considerable proportions in the brain (100-150 mg/100 g of fresh tissue).

One of the most metabolically active amino acids.

Glutamic acid is one of the most abundant amino acids in the body and a wild card for energy exchange between tissues. It is considered a non-essential amino acid because it can be synthesized in many tissues, having a fundamental role in cell growth and maintenance.

It is a substrate for protein synthesis and a precursor of anabolic metabolism in muscle while regulating acid/base balance in the kidney and urea production in the liver. It is also involved in the transport of nitrogen between different organs.

The cells of the intestinal mucosa are voracious consumers of this amino acid, just as the cells of the immune system require it as a source of energy. Finally, glutamic acid is a precursor for the synthesis of a metabolite with high antioxidant potential, such as glutathione production.

Several studies have shown that the stomach, intestine, pancreas and spleen consume 95% of the glutamic acid ingested in the diet, so it is important to eat a diet rich in protein so as not to alter the balance of amino acids with access to the rest from the body after this initial passage of nutrients through the digestive system.

In its free form it produces a specific and peculiar flavor known as umami.

Just as it is a key amino acid in our body, it is also for other living beings, both of animal and plant origin, so there are many foods rich in glutamic acid that, when combined with a healthy and balanced diet, produce a pleasant taste. In the food industry, it is used as a flavor enhancer in seasonings and condiments (E621, monosodium glutamate).

In addition to this, glutamate could be involved in the release of GnRH (gonadotropin-releasing hormone) essential for brain and body dimorphism. Indeed, a decrease in GABA coupled with an increase in glutamate coincides with an increase in GnRH release. In the same way, it is known that when puberty begins, glutaminase, the enzyme responsible for the synthesis of glutamate, increases, which in turn stimulates or controls the pulsatility of GnRH through NMDA receptors.

A study conducted at Michigan State University found that inflammation in the brain can produce high levels of glutamate which in turn can lead to suicidal thoughts in the affected person.

History

Although found naturally in many foods, the contributions to flavor made by glutamic acid and other amino acids were only scientifically identified in the early 20th century. This substance was discovered and identified in 1866, by German chemist Karl Heinrich Ritthausen who treated wheat gluten (for which it was named) with sulfuric acid. In 1908, Japanese researcher Kikunae Ikeda of Tokyo Imperial University identified the brown crystals left after evaporation of a large amount of kombu broth as glutamic acid. These crystals, when tasted, reproduced the difficult to describe, but undeniable taste found in many foods, especially seaweed. Professor Ikeda called this taste umami. He subsequently designed and patented a method for large-scale production of glutamic acid in the form of a crystalline salt, monosodium glutamate.