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Glutamic acid

Glutamic acid (symbol Glu or E) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is non-essential in humans, meaning the body can synthesize it. It is also an excitatory neurotransmitter, in fact the most abundant one, in the vertebrate nervous system.

Glutamic Acid, Twenty Years Later

Glutamic acid is a non-essential amino acid that plays a crucial role in various biological processes. It is one of the 20 standard amino acids used by cells to synthesize proteins. This amino acid is not only vital for protein synthesis but also serves as a key neurotransmitter in the brain, making it essential for proper cognitive function.

Chemical Structure and Properties

Glutamic acid, often abbreviated as Glu or E, has the chemical formula C5H9NO4. It is characterized by its side chain carboxylic acid group, which gives it an acidic nature. This property allows glutamic acid to donate protons, making it an important player in maintaining the acid-base balance in the body. The presence of both an amino group and a carboxyl group makes it amphoteric, meaning it can act as both an acid and a base.

Biological Functions

Protein Synthesis

As a building block of proteins, glutamic acid is incorporated into proteins during translation. It is encoded by the codons GAA and GAG in the genetic code. Proteins containing glutamic acid are involved in a wide range of functions, from structural roles in cells to enzymatic activities.

Neurotransmitter Role

Glutamic acid is a major excitatory neurotransmitter in the central nervous system. It is involved in cognitive functions such as learning and memory. The neurotransmitter form of glutamic acid is known as glutamate. It binds to specific receptors in the brain, such as NMDA, AMPA, and kainate receptors, facilitating synaptic transmission and plasticity.

Metabolic Pathways

Glutamic acid is a key component in the Krebs cycle, also known as the citric acid cycle, which is crucial for energy production in cells. It can be converted into alpha-ketoglutarate, an important intermediate in this cycle. Additionally, glutamic acid is involved in the synthesis of other amino acids, such as proline and arginine, and is a precursor for the synthesis of the antioxidant glutathione.

Dietary Sources

Glutamic acid is abundant in both plant and animal proteins. Some rich dietary sources include:

Fermented foods, such as soy sauce and miso, are particularly high in glutamic acid due to the breakdown of proteins during fermentation.

Health Implications

Cognitive Health

Due to its role as a neurotransmitter, adequate levels of glutamic acid are essential for maintaining cognitive health. Imbalances in glutamate levels have been associated with neurological disorders such as Alzheimer's disease, Parkinson's disease, and epilepsy. Research is ongoing to understand the precise mechanisms by which glutamic acid influences these conditions.

Muscle Function

Glutamic acid is involved in the synthesis of creatine, a compound that helps supply energy to muscle cells. This makes it important for muscle function and endurance. Athletes and bodybuilders often focus on maintaining adequate levels of glutamic acid to support muscle recovery and performance.

Immune System Support

Glutamic acid plays a role in supporting the immune system. It is involved in the production of glutathione, a powerful antioxidant that helps protect cells from oxidative stress and supports immune function. Maintaining adequate levels of glutamic acid can contribute to a robust immune response.

Glutamic Acid in Food Industry

Glutamic acid is widely used in the food industry as a flavor enhancer. Its sodium salt form, monosodium glutamate (MSG), is commonly added to foods to enhance their umami flavor. While MSG is generally recognized as safe by food safety authorities, some individuals may experience sensitivity to it, leading to symptoms such as headaches and nausea, often referred to as "Chinese restaurant syndrome."

FROM DUKE'S DATABASE

Biological Activities

Antialkali? Dosage: 500-1,000 mg/day/orl/man; Reference: M29

Antiepileptic

Antihyperammonemic Reference: M29

Antilithic Reference: PAM

Antiprostatitic Dosage: 125-250 mg 3 x/day; Reference: WER

Antiretardation Reference: JBH

Anxiolytic Reference: M11

Neurotoxic Reference: JBH

Plant species with highest amount

Ceratonia siliqua L. -- Carob, Locust Bean, St.John's-Bread; 131,600 ppm in Seed;

Lupinus albus L. -- White Lupine; 21,650 - 96,985 ppm in Seed;

Glycine max (L.) MERR. -- Soybean; 70,680 - 77,280 ppm in Seed;

Brassica chinensis L. -- Bok-Choy, Celery Cabbage, Celery Mustard, Chinese Cabbage, Chinese Mustard, Chinese White Cabbage, Pak-Choi; 3,600 - 76,932 ppm in Leaf;

Cucurbita foetidissima HBK. -- Buffalo Gourd; 52,800 - 73,530 ppm in Seed JEL EB32:87;

Allium schoenoprasum L. -- Chives; 5,790 - 72,385 ppm in Leaf;

Arachis hypogaea L. -- Groundnut, Peanut; 54,650 - 65,281 ppm in Seed;

Asparagus officinalis L. -- Asparagus; 5,010 - 64,645 ppm in Shoot;

Triticum aestivum L. -- Wheat; 39,000 - 63,000 ppm in Seed;

Juglans cinerea L. -- Butternut; 60,840 - 62,942 ppm in Seed;

Prunus dulcis (MILLER) D. A. WEBB -- Almond; 59,340 - 62,070 ppm in Seed;

Pinus pinea L. -- Italian Stone Pine, Pignolia; 40,840 - 59,800 ppm in Seed JEL USA;

Cnidoscolus chayamansa McVAUGH -- Chaya; 11,780 - 58,900 ppm in Leaf;

Cajanus cajan (L.) HUTH -- Pigeonpea; 40,790 - 56,270 ppm in Seed;

Phaseolus vulgaris subsp. var. vulgaris -- Black Bean, Dwarf Bean, Field Bean, Flageolet Bean, French Bean, Garden Bean, Green Bean, Haricot, Haricot Bean, Haricot Vert, Kidney Bean, Navy Bean, Pop Bean, Popping Bean, Snap Bean, String Bean, Wax Bean; 5,120 - 55,054 ppm in Sprout Seedling;

Acacia farnesiana (L.) WILLD. -- Cassie, Huisache, Opopanax, Popinac, Sweet Acacia; 10,080 - 54,070 ppm in Leaf;

Lycopersicon esculentum MILLER -- Tomato; 90 - 54,053 ppm in Fruit;

Sinapis alba L. -- White Mustard; 49,790 - 53,275 ppm in Seed;

Citrullus lanatus (THUNB.) MATSUM. & NAKAI -- Watermelon; 53,000 ppm in Seed;

Rehmannia glutinosa (GAERTN.) LIBOSCH. -- Chinese Foxglove; 2,000 - 53,000 ppm in Root;

Sesamum indicum L. -- Ajonjoli (Sp.), Beni, Benneseed, Sesame, Sesamo (Sp.); 24,670 - 51,927 ppm in Seed;

Pistacia vera L. -- Pistachio; 49,160 - 51,139 ppm in Seed;

Lens culinaris MEDIK. -- Lentil; 43,500 - 49,000 ppm in Seed;

Papaver somniferum L. -- Opium Poppy, Poppyseed Poppy; 45,410 - 48,713 ppm in Seed;

Moringa oleifera LAM. -- Ben Nut, Benzolive Tree, Drumstick Tree, Horseradish Tree, Jacinto (Sp.), Moringa, West Indian Ben; 10,350 - 48,500 ppm in Shoot USA;

Vigna radiata (L.) WILCZEK -- Green Gram, Mungbean; 42,640 - 46,883 ppm in Seed;

Cucurbita pepo L. -- Pumpkin; 43,150 - 46,358 ppm in Seed;

Vicia faba L. -- Broadbean, Faba Bean, Habas; 8,550 - 45,000 ppm in Seed;

Pisum sativum L. -- Pea; 4,480 - 44,313 ppm in Fruit;

Trigonella foenum-graecum L. -- Alholva (Sp.), Bockshornklee (Ger.), Fenugreek, Greek Clover, Greek Hay; 39,880 - 43,870 ppm in Seed;

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