Glutamic acid

(S)- glutamic acid
L-( ) -glutamic acid
D-(- ) -glutamic acid
(R) -glutamic acid
2- Aminopentandisäure
α - aminoglutaric
E 620 ( a food additive )
Abbreviations: Glu ( Three letter code)
E ( single letter code )

56-86-0 (L- enantiomer)
6893-26-1 (D - enantiomer)
617-65-2 (DL- glutamic acid)

White solid

Fixed

1.54 g · cm -3 ( 20 ° C)

160 ° C.

Decomposition at 205 ° C

PKCOOH: 2.16
PKγ -COOH: 4.32
PKNH2: 9.96

Poorly in water ( 11.1 g · l-1 at 25 ° C)
Poorly in ethanol, insoluble in diethyl ether, acetone and glacial acetic acid

12961 mg · kg -1 ( LD50, mouse, oral)

Template: Infobox chemical / molecular formula search available

Glutamic acid, abbreviated as Glu or E (including α - aminoglutaric, 2- aminoglutaric ) is a proteinogenic, not essential for the human α -amino acid and may be in the form of two mirror image (enantiomers ) are present. In the three-letter code has been designated as Glu and in single letter e. It is an important building block of proteins. Its salts and esters are called glutamates. In biology and medicine, the glutamic acid is usually called glutamate, since the compound is dissociated in the body. Furthermore, glutamate is one of the major excitatory neurotransmitter in the central nervous system (CNS). As a food additive, L - glutamic acid ( E 620 ) and some of its salts (see Glutamate ) used as a flavor enhancer, especially in Asian cuisine and convenience products.

If it is mentioned in this text or in the scientific literature " glutamic acid " without further suffix (prefix ), L- glutamic acid is meant.

5.1 Significance in the citric acid cycle
5.2 glutamic acid ( glutamate ) in the blood findings ( amino acids concentrations)
5.3 insomnia, restless legs syndrome and glutamic acid

Stereochemistry

In nature is essentially only the L-( )- glutamic acid [ synonym: (S) -glutamic acid ] before. On the D-( -)- glutamic acid [ synonym: (R) -glutamic acid ] and the racemic mixture of two enantiomers will not be discussed in this article.

Occurrence

L -glutamic acid is found in most proteins present in different proportions and is present in each protein-containing foods. The following examples relate in each case to 100 g of the food, in addition, the percentage of glutamic acid is specified in total protein. Particularly rich in free L- glutamate are cheese and meat products.

Properties

The isoelectric point of glutamic acid is 3.24. The dicarboxylic acid dissolves only slightly in water ( ~ 11 g / l at 25 ° C) and ethanol; the solution is strongly acidic ( pKCOOH 2.16, pKγ -COOH 4.32 ).

Production

L -glutamic acid is commercially produced exclusively by fermentation method ( soy sauce, liquid seasoning ). It all started when was systematically researched by wild-type organisms in which L -glutamic acid using cheaper culture media ( starting materials) and culture conditions ( temperature, concentration of trace elements, etc.) could accumulate. The fermentation method was optimized by use of mutants.

Derivatives

By heating a mixture of equal parts by weight of glutamic acid, and water in an autoclave, to obtain the elimination of water at reaction temperatures of 135-143 ° C and pyroglutamic acid, a cyclic amide ( lactam ).

Physiological significance

As with all other amino acids, only the L- isomer is used in the metabolism of the human body as a component also in glutamate. A proteinogenic α - amino acid is L -glutamic acid is a component of proteins. In addition, she plays so far in cell metabolism an essential role, as she stands on the citric acid cycle in connection to carbohydrate metabolism. In addition, L-glutamic acid is used for the production of other amino acids.

L -glutamic acid binds the released during protein and amino acid degradation cytotoxin ammonia to form glutamine by the following reaction:

L- Glutamate is the primary excitatory neurotransmitter in the central nervous system of vertebrates. It is presynaptically released and binds to specific postsynaptic glutamate receptors. In the central nervous system can be decarboxylated to γ -aminobutyric acid ( GABA), L-glutamic acid by the enzyme, L- glutamic acid, which is used as a neurotransmitter at inhibitory synapses. L-glutamic acid is the only amino acid which is oxidized in the brain, transamination, decarboxylation and aminated.

Importance in the Citric Acid Cycle

L-glutamate formed in the citric acid cycle of α -ketoglutarate ( αKG ), and an ammonium ion, by the reaction of the enzyme glutamate dehydrogenase (GDH ) (1). Another ammonium ion can be trapped by the reaction of glutamine synthetase ( GLN ), where glutamine is formed ( 3). Both reactions are spontaneous detoxification of all tissues in the brain and are of particular importance.

The final decontamination ammonium ions need to be supplied to the urea cycle. This is carried out by transmitting ( transaminating ) to oxaloacetate (OA ) (2), as well as through the glutamate dehydrogenase reaction (1). Glutamine can be reacted with α -ketoglutarate into plants to two molecules of L -glutamic acid (3 ) and thus fed to the GDH reaction. This reaction is catalysed by glutamate synthase ( Glu ).

The amino acid L- glutamic acid synthesis of NH 2 -donor is in a transamination reaction. These α -keto acids converted into the homologous α -amino acids. Examples include glutamic-oxaloacetic transaminase (GOT ) (2), and glutamate - pyruvate transaminase (GPT). Coenzyme pyridoxal phosphate. For almost all other amino groups are required in the metabolism, glutamine is the donor.

Glutamic acid ( glutamate ) in the blood findings ( amino acids concentrations)

The reference intervals (normal values) for glutamic acid in the blood findings are in mol / ml in infants 20-107, in children 18-65 and adults 28-92. As therapy at very high Glutaminsäurewerten ( glutamate ) in the blood findings, such as those the Chinese restaurant syndrome or in cases of eczema and / or histamine intolerance can occur, recommends Prof. Reinhart Jarisch a vitamin B6 administration in the order of 0.5 mg / kg body weight per day. This also promotes the body's synthesis of diamine oxidase (DAO ) and fought so cause the effects of histamine intolerance.

Insomnia, restless legs syndrome and glutamic acid

Many patients with Restless Legs Syndrome (RLS ) also suffer from insomnia. A study of 28 RLS patients at Johns Hopkins University ( Baltimore) provided information on the connection of the treatment of Restless Legs Syndrome with insomnia and the cerebral metabolism of the neurotransmitters dopamine and glutamate. In the treatment of RLS with drugs that increase the levels of dopamine, the RLS symptoms at the same time an often existing insomnia but not improved. The comparison of these patients with 20 healthy volunteers showed an unusually high levels of glutamate in the thalamus of the treated RLS patients. The height of the glutamate level was correlated with the perception of poor sleep. The physicians of the Johns Hopkins University hold the over-excitation of the thalamus by glutamate for the cause of insomnia.

Salts

The different salts of glutamic acid are known as food additives. There are various salts of glutamic acid, called flavor enhancer E 621 to E 625 are used.

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