Glutamic acid

Structural formula
Structure of naturally occurring L- glutamic acid
General
Surname	Glutamic acid
other names	2-aminopentanedioic acid α-aminoglutaric acid E  620 GLUTAMIC ACID ( INCI ) Abbreviations: Glu ( three letter code ) E (one -letter code )
Molecular formula	C 5 H 9 NO 4
Brief description	white solid
External identifiers / databases
CAS number 617-65-2 ( DL -glutamic acid) EC number 210-522-2 ECHA InfoCard 100.009.567 PubChem 611 Wikidata Q181136
Drug information
ATC code	V06  A09
properties
Molar mass	147.13 g · mol -1
Physical state	firmly
density	1.54 g cm −3 (20 ° C)
Melting point	160 ° C
boiling point	Decomposes at 205 ° C
pK s value	pK COOH : 2.16 pK γ-COOH : 4.32 pK NH 3 + : 9.96
solubility	poor in water (11.1 g l −1 at 25 ° C) poor in ethanol , insoluble in diethyl ether , acetone and acetic acid
safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
Toxicological data	12961 mg kg −1 ( LD 50 ,  mouse ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Glutamic acid (including α-aminoglutaric acid , 2-aminoglutaric acid ) is an α - amino acid , in the two Spiegelbildisomeren ( enantiomers occurs), one of which proteinogenic form of the human organism itself can produce (not essential amino acid). It is called Glu in the three -letter code and E in the one -letter code . Their salts and esters are called glutamates . In biology and medicine, glutamic acid is usually called glutamate because the compound is dissociated in the body . Glutamic acid is an important building block of proteins ; In addition, glutamate is one of the most important excitatory neurotransmitters in the central nervous system (CNS) of the human organism. As a food additive , L- glutamic acid (E 620) and some of its salts (see glutamates ) are used as flavor enhancers , especially in Asian cuisine and convenience products .

Stereochemistry

Amino acids are chiral molecules. Essentially only L - (+) - glutamic acid [synonym: ( S ) -glutamic acid] occurs in nature . If “glutamic acid” is mentioned in this text or in the scientific literature without any additional name ( prefix ), L- glutamic acid is meant.

The D - (-) - glutamic acid [Synonym: ( R ) -glutamic acid] can be produced by chemical means. They and the racemate from both enantiomers are not discussed in detail in this article.

Isomers of glutamic acid
Surname	L -glutamic acid	D -glutamic acid
other names	( S ) -glutamic acid (+) - glutamic acid	( R ) -Glutamic acid (-) - Glutamic acid
Structural formula
CAS number	56-86-0	6893-26-1
	617-65-2 ( DL )
EC number	200-293-7	230-000-8
	210-522-2 ( DL )
ECHA info card	100,000,267	100.027.273
	100.009.567 ( DL )
PubChem	33032	23327
	611 ( DL )
DrugBank	DB00142
	- ( DL )
Wikidata	Q26995161	Q27077040
	Q181136 ( DL )

Occurrence

L- glutamic acid occurs in different proportions in most proteins and is present in every protein-containing food . The following examples each relate to 100 g of the food; the percentage of glutamic acid in the total protein is also given. Cheese and meat products are particularly rich in free L -glutamate.

Food	protein	Glutamic acid	proportion of
Beef , raw	21.26 g	3191 mg	15.0%
Chicken breast fillet , raw	23.09 g	3458 mg	15.0%
Salmon , raw	20.42 g	2830 mg	13.9%
Chicken egg	12.58 g	1676 mg	13.3%
Cow's milk , 3.7% fat	0 3.28 g	0 687 mg	20.9%
Walnuts	15.23 g	2816 mg	18.5%
Wholemeal wheat flour	13.21 g	4328 mg	32.8%
Wholemeal corn flour	0 6.93 g	1300 mg	18.8%
Rice , unpeeled	0 7.94 g	1618 mg	20.4%
Peas , dried	24.55 g	4196 mg	17.1%
Tomato puree	0 1.65 g	0 658 mg	39.9%

history

By digesting gluten with sulfuric acid , the German chemist Heinrich Ritthausen succeeded in isolating glutamic acid for the first time in 1866 at the Agricultural Academy in Waldau near Königsberg. Gustav Werther , professor of chemistry in Königsberg at the time, was able to correctly determine the composition of glutamic acid using the crystals given to him by Ritthausen . After Ritthausen moved to the Agricultural Academy in Bonn-Poppelsdorf, he arranged for the chemist Wilhelm Dittmar to investigate the structure, which Dittmar succeeded in 1872. The results were confirmed by Ludwig Wolff in 1890 .

properties

Glutamate zwitterion
at pH 7.4 with the side chain in blue

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

Manufacturing

L- glutamic acid is commercially produced exclusively using the fermentation method ( soy sauce , liquid seasoning ). It began with a systematic search for wild-type organisms in which L- glutamic acid could be enriched using suitable nutrient media (starting materials) and culture conditions (temperature, concentration of trace elements, etc.). The fermentation method was optimized by using mutants.

Derivatives

When a mixture of equal parts by weight of glutamic acid and water is heated in an autoclave, pyroglutamic acid , a cyclic amide ( lactam ) , is obtained with elimination of water at reaction temperatures of 135-143 ° C.

Physiological importance

As with all other amino acids, only the L isomer is used as a building block in the metabolism of the human body for glutamate . As a proteinogenic α-amino acid, L- glutamic acid is a component of proteins. In addition, it plays an essential role in cell metabolism in that it is linked to carbohydrate metabolism via the citric acid cycle . In addition, L- glutamic acid is used to form other amino acids.

L -glutamic acid binds the cell toxin ammonia , which is released during protein and amino acid degradation, with the formation of glutamine through the following reaction:

α-ketoglutarate → glutamic acid → glutamine

L -glutamate is the most important excitatory neurotransmitter in the central nervous system of vertebrates . It is released presynaptically and binds postsynaptically to specific glutamate receptors . In the central nervous system, L-glutamic acid can be decarboxylated to γ-aminobutyric acid (GABA) by the enzyme L-glutamic acid decarboxylase, which acts as a neurotransmitter at inhibitory synapses. L -glutamic acid is the only amino acid that is oxidized, transaminated , aminated and decarboxylated in the brain .

Meaning in the citric acid cycle

Key role of glutamate (Glu) in amination / deamination ( 1 ) and in transamination reactions ( 2 ). The interrelationships with glutamine (Gln) are shown peripherally in abbreviated form ( 3 ).

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

For final detoxification, ammonium ions must be added to the urea cycle. This takes place both through transfer ( transamination ) to oxaloacetate (OA) ( 2 ) and via the glutamate dehydrogenase reaction ( 1 ). Glutamine can be converted with α-ketoglutarate in plants into two molecules of L- glutamic acid ( 3 ) and thus supplied to the GDH reaction. This reaction is catalyzed by glutamate synthase (GluS).

The amino acid synthesis is L -glutamic acid of the NH ₂ - donor in a transamination. This converts α-keto acids into the homologous α- amino acids . Examples are glutamate oxaloacetate transaminase (GOT) ( 2 ) and glutamate pyruvate transaminase (GPT). Coenzyme is pyridoxal phosphate . Glutamine is the donor for almost all other amino groups that are required in the metabolism.

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

The reference ranges (normal values) for glutamic acid in blood findings are in µmol / ml in infants 20–107, in children 18–65 and in adults 28–92. As a therapy for very high levels of glutamic acid (glutamate) in the blood, as it is e.g. B. in the Chinese restaurant syndrome or eczema and / or histamine intolerance , Reinhart Jarisch recommends a vitamin B6 dose in the order of 0.5 mg / kg body weight per day. This also promotes the body's own synthesis of diamine oxidase (DAO) and thus combats the causal effects of histamine intolerance.

Salts

→ Main article : Glutamates

The various salts of glutamic acid are known as food additives . Various salts of glutamic acid with the designation flavor enhancers E 621 to E 625 are used.

Web links

Commons : Glutamic Acid  - Collection of pictures, videos and audio files

Wikibooks: Biosynthesis and Degradation of L-Glutamic Acid  - Learning and Teaching Materials

Individual evidence

1. ↑ Entry on E 620: Glutamic acid in the European database on food additives, accessed on June 27, 2020.
2. ↑ Entry on GLUTAMIC ACID in the CosIng database of the EU Commission, accessed on August 11, 2020.
3. ↑ ^{a b c d e f g} Entry on glutamic acid in the GESTIS substance database of the IFA , accessed on June 21, 2019(JavaScript required) .
4. ↑ ^{a b c d} Hans-Dieter Jakubke and Hans Jeschkeit: Amino acids, peptides, proteins , Verlag Chemie, Weinheim, 1982, ISBN 3-527-25892-2 , p. 40.
5. ↑ Entry on glutamic acid. In: Römpp Online . Georg Thieme Verlag, accessed on December 9, 2014.
6. ^ Joint FAO / WHO Expert Committee on Food Additives (JECFA), Monograph for Glutamic acid and its salts , accessed on December 9, 2014.
7. ↑ ^{a b} ZZulV : Annex 4 (to Section 5, Paragraph 1 and Section 7) Limited additives .
8. ↑ nutrient database of the US Department of Agriculture , 21st edition.
9. ↑ KH Ritthausen: About the glutamic acid , Journal Prakt Chem, Volume 99 (6-7), p. 454ff (1866).
10. ↑ Sabine Hansen: The discovery of proteinogenic amino acids from 1805 in Paris to 1935 in Illinois. ( Memento from June 15, 2016 in the Internet Archive ) Berlin 2015.
11. ↑ W. Dittmar: About the reduction of glutanic acid by hydrogen iodide , Journal Prakt Chem, Volume 5 (7), p. 308ff (1872).
12. ↑ L. Wolff: About glyoxylpropionic acid and some derivatives of the same. Liebigs Annalen der Chemie, Volume 260, pp. 79ff (1890).
13. ↑ PM Hardy: The Protein Amino Acids in GC Barrett (editor): Chemistry and Biochemistry of the Amino Acids , Chapman and Hall, 1985, ISBN 0-412-23410-6 , p. 9.
14. ↑ Izumi, Y. et al. (1979): Production and Use of Amino Acids . In: Angewandte Chemie 90 (3); 187-194; doi : 10.1002 / anie.19780900307 .
15. ↑ Helmut Greiling, AM Gressner: Textbook of clinical chemistry and pathobiochemistry. Schattauer Verlagsgesellschaft, 1987, ISBN 3-79-450949-8 , 1197 pages.
16. ↑ Reinhart Jarisch: Histamine intolerance, histamine and seasickness. 2nd edition, Thieme Verlag, Stuttgart New York, 2004, ISBN 3-13-105382-8 , p. 151.

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !