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Glutamic acid (Glu), also known as L-glutamic acid or as glutamate, the name of its anion, is an alpha-amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. L-glutamic acid is one of 20 proteinogenic amino acids, i.e., the amino acids used in the biosynthesis of proteins. Glutamic acid is found in all organisms ranging from bacteria to plants to animals. It is classified as an acidic, charged (at physiological pH), aliphatic amino acid. In humans it is a non-essential amino acid and can be synthesized via alanine or aspartic acid via alpha-ketoglutarate and the action of various transaminases. Glutamate also plays an important role in the body's disposal of excess or waste nitrogen. Glutamate undergoes deamination, an oxidative reaction catalysed by glutamate dehydrogenase leading to alpha-ketoglutarate. In many respects glutamate is a key molecule in cellular metabolism. Glutamate is the most abundant fast excitatory neurotransmitter in the mammalian nervous system. At chemical synapses, glutamate is stored in vesicles. Nerve impulses trigger release of glutamate from the pre-synaptic cell. In the opposing post-synaptic cell, glutamate receptors, such as the NMDA receptor, bind glutamate and are activated. Because of its role in synaptic plasticity, it is believed that glutamic acid is involved in cognitive functions like learning and memory in the brain. Glutamate transporters are found in neuronal and glial membranes. They rapidly remove glutamate from the extracellular space. In brain injury or disease, they can work in reverse and excess glutamate can accumulate outside cells. This process causes calcium ions to enter cells via NMDA receptor channels, leading to neuronal damage and eventual cell death, and is called excitotoxicity. The mechanisms of cell death include: Damage to mitochondria from excessively high intracellular Ca2+. Glu/Ca2+-mediated promotion of transcription factors for pro-apoptotic genes, or downregulation of transcription factors for anti-apoptotic genes. Excitotoxicity due to glutamate occurs as part of the ischemic cascade and is associated with stroke and diseases like amyotrophic lateral sclerosis, lathyrism, and Alzheimer's disease. Glutamic acid has been implicated in epileptic seizures. Microinjection of glutamic acid into neurons produces spontaneous depolarization around one second apart, and this firing pattern is similar to what is known as paroxysmal depolarizing shift in epileptic attacks. This change in the resting membrane potential at seizure foci could cause spontaneous opening of voltage activated calcium channels, leading to glutamic acid release and further depolarization (http://en.wikipedia.org/wiki/Glutamic_acid). Glutamate was discovered in 1866 when it was extracted from wheat gluten (from where it got its name. Glutamate has an important role as a food additive and food flavoring agent. In 1908, Japanese researcher Kikunae Ikeda identified brown crystals left behind after the evaporation of a large amount of kombu broth (a Japanese soup) as glutamic acid. These crystals, when tasted, reproduced a salty, savory flavor detected in many foods, most especially in seaweed. Professor Ikeda termed this flavor umami. He then patented a method of mass-producing a crystalline salt of glutamic acid, monosodium glutamate.

2-Amino-3-methylbutanoic acid

Valine (Val) or L-valine is an alpha-amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. L-valine is one of 20 proteinogenic amino acids, i.e., the amino acids used in the biosynthesis of proteins. Valine is found in all organisms ranging from bacteria to plants to animals. It is classified as a non-polar, uncharged (at physiological pH) aliphatic amino acid. Valine was first isolated from casein in 1901 by Hermann Emil Fischer. The name valine comes from valeric acid, which in turn is named after the plant valerian due to the presence of valine in the roots of the plant. Valine is essential in humans, meaning the body cannot synthesize it, and it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, beans and legumes. L-valine is a branched chain amino acid (BCAA). The BCAAs consist of leucine, valine and isoleucine (and occasionally threonine). BCAAs are essential amino acids whose carbon structure is marked by a branch point at the beta-carbon position. BCAAs are critical to human life and are particularly involved in stress, energy and muscle metabolism. BCAA supplementation as therapy, both oral and intravenous, in human health and disease holds great promise. BCAAs have different metabolic routes, with valine going solely to carbohydrates (glucogenic), leucine solely to fats (ketogenic) and isoleucine being both a glucogenic and a ketogenic amino acid. The different metabolism accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg and 16 mg/kg of valine, leucine and isoleucine respectively. Like other branched-chain amino acids, the catabolism of valine starts with the removal of the amino group by transamination, giving alpha-ketoisovalerate, an alpha-keto acid, which is converted to isobutyryl-CoA through oxidative decarboxylation by the branched-chain α-ketoacid dehydrogenase complex. This is further oxidised and rearranged to succinyl-CoA, which can enter the citric acid cycle. Furthermore, these amino acids have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. Many types of inborn errors of BCAA metabolism exist, and are marked by various abnormalities. The most common form is the maple syrup urine disease, marked by a characteristic urinary odor. Other abnormalities are associated with a wide range of symptoms, such as mental retardation, ataxia, hypoglycemia, spinal muscle atrophy, rash, vomiting and excessive muscle movement. Most forms of BCAA metabolism errors are corrected by dietary restriction of BCAA and at least one form is correctable by supplementation with 10 mg of biotin daily. BCAA are decreased in patients with liver disease, such as hepatitis, hepatic coma, cirrhosis, extrahepatic biliary atresia or portacaval shunt. Valine in particular, has been established as a useful supplemental therapy to the ailing liver. Valine, like other branched-chain amino acids, is associated with insulin resistance: higher levels of valine are observed in the blood of diabetic mice, rats, and humans (PMID: 25287287). Mice fed a valine deprivation diet for one day have improved insulin sensitivity and feeding of a valine deprivation diet for one week significantly decreases blood glucose levels (PMID: 24684822). In diet-induced obese and insulin resistant mice, a diet with decreased levels of valine and the other branched-chain amino acids results in reduced adiposity and improved insulin sensitivity (PMID: 29266268). In sickle-cell disease, valine substitutes for the hydrophilic amino acid glutamic acid in hemoglobin. Because valine is hydrophobic, the hemoglobin does not fold correctly. Hypervalinemia is another example of an inborn error of metabolism involving valine.

An alpha-amino acid that is pyrrolidine bearing a carboxy substituent at position 2." []

Proline (Pro), also known as L-proline is an alpha-amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. Proline is one of 20 proteinogenic amino acids, i.e., the amino acids used in the biosynthesis of proteins. Proline is found in all organisms ranging from bacteria to plants to animals. It is classified as an aliphatic, non-polar amino acid. Proline is sometimes called an imino acid, although the IUPAC definition of an imine requires a carbon-nitrogen double bond. Proline is a non-essential amino acid that is synthesized from glutamic acid. It is an essential component of collagen and is important for proper functioning of joints and tendons. Proline is derived from the amino acid L-glutamate in which glutamate-5-semialdehyde is first formed by glutamate 5-kinase and glutamate-5-semialdehyde dehydrogenase (which requires NADH or NADPH). This semialdehyde can then either spontaneously cyclize to form 1-pyrroline-5-carboxylic acid, which is reduced to proline by pyrroline-5-carboxylate reductase, or turned into ornithine by ornithine aminotransferase, followed by cyclization by ornithine cyclodeaminase to form proline. L-Proline has been found to act as a weak agonist of the glycine receptor and of both NMDA and non-NMDA ionotropic glutamate receptors. It has been proposed to be a potential endogenous excitotoxin/neurotoxin. Studies in rats have shown that when injected into the brain, proline non-selectively destroys pyramidal and granule cells (PMID: 3409032 ). Therefore, under certain conditions proline can act as a neurotoxin and a metabotoxin. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of proline are associated with at least five inborn errors of metabolism, including hyperprolinemia type I, hyperprolinemia type II, iminoglycinuria, prolinemia type II, and pyruvate carboxylase deficiency. People with hyperprolinemia type I often do not show any symptoms even though they have proline levels in their blood between 3 and 10 times the normal level. Some individuals with hyperprolinemia type I exhibit seizures, intellectual disability, or other neurological or psychiatric problems. Hyperprolinemia type II results in proline levels in the blood between 10 and 15 times higher than normal, and high levels of a related compound called pyrroline-5-carboxylate. Hyperprolinemia type II has signs and symptoms that vary in severity and is more likely than type I to involve seizures or intellectual disability.

Sucrose is a nonreducing disaccharide composed of glucose and fructose linked via their anomeric carbons. It is obtained commercially from sugarcane (Saccharum officinarum), sugar beet (Beta vulgaris), and other plants and used extensively as a food and a sweetener. Sucrose is derived by crushing and extracting sugarcane with water or by extracting sugar beet with water, evaporating, and purifying with lime, carbon, and various liquids. Sucrose is also obtainable from sorghum. Sucrose occurs in low percentages in honey and maple syrup. Sucrose is used as a sweetener in foods and soft drinks, in the manufacture of syrups, in invert sugar, confectionery, preserves and jams, demulcent, pharmaceutical products, and caramel. Sucrose is also a chemical intermediate for detergents, emulsifying agents, and other sucrose derivatives. Sucrose is widespread in the seeds, leaves, fruits, flowers, and roots of plants, where it functions as an energy store for metabolism and as a carbon source for biosynthesis. The annual world production of sucrose is in excess of 90 million tons mainly from the juice of sugar cane (20%) and sugar beet (17%). In addition to its use as a sweetener, sucrose is used in food products as a preservative, antioxidant, moisture control agent, stabilizer, and thickening agent. BioTransformer predicts that sucrose is a product of 6-O-sinapoyl sucrose metabolism via a hydrolysis-of-carboxylic-acid-ester-pattern1 reaction occurring in human gut microbiota and catalyzed by the liver carboxylesterase 1 (P23141) enzyme (PMID: 30612223).

Norvaline is a non-proteinogenic branched-chain amino acid with the chemical formula C5H11NO2, isomeric with valine. It has previously been reported to be a natural component of an antifungal peptide of Bacillus subtilis. Norvaline and other modified branched chain amino acids have received attention in recent studies, as they appear to be incorporated in some recombinant proteins found in E. coli. This amino acid is often made synthetically.

D-proline is an isomer of the naturally occurring amino acid, L-Proline. D-amino acids have been found in relatively high abundance in human plasma and saliva (PMID: 16480744). These amino acids may be of bacterial origin, but there is also evidence that they are endogenously produced through amino acid racemase activity (PMID: 1426150).

There are two forms of glutamic acid found in nature: L-glutamic acid and D-glutamic acid. D-glutamic acid, is not endogenously produced in higher mammals. It is found naturally primarily in the cell walls of certain bacteria. D-glutamate is also present in certain foods e.g., soybeans and also arises from the turnover of the intestinal tract microflora, whose cell walls contain significant D-glutamate. Unlike other D-amino acids, D-glutamate is not oxidized by the D-amino acid oxidases, and therefore this detoxification pathway is not available for handling D-glutamate. Likewise, D-glutamic acid, when ingested, largely escapes most deamination reactions (unlike the L-counterpart). Free D-glutamate is found in mammalian tissue at surprisingly high levels, with D-glutamate accounting for 9% of the total glutamate present in liver. D-glutamate is the most potent natural inhibitor of glutathione synthesis identified to date and this may account for its localization to the liver, since circulating D-glutamate may alter redox stabiity (PMID 11158923). Certain eels are known to use D-glutamic acid as a phermone for chemical communication. D-Glutamic acid has been found to be a metabolite of Lactobacillus (PMID: 22754309).

Neurine is a citraconoyl group.

2S-amino-pentanoic acid

N-Methyl-a-aminoisobutyric acid, also known as 2-(methylamino)isobutyrate or AMAIB, belongs to the class of organic compounds known as alpha amino acids. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). N-Methyl-a-aminoisobutyric acid is a drug. N-Methyl-a-aminoisobutyric acid is a metabolite that is actively incorporated into the cell by the actions of Interleukin 1-beta and Interleukin 6 via sodium dependent transport systems (PMID 16202926).

DL-Glutamate, also known as E or DL-glutamic acid, belongs to the class of organic compounds known as glutamic acid and derivatives. Glutamic acid and derivatives are compounds containing glutamic acid or a derivative thereof resulting from reaction of glutamic acid at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). DL-Glutamate exists in all living organisms, ranging from bacteria to humans. DL-Glutamate is found, on average, in the highest concentration within a few different foods, such as red bell peppers, milk (cow), and wheats and in a lower concentration in eggplants, romaine lettuces, and nanking cherries. DL-Glutamate has also been detected, but not quantified, in a few different foods, such as apples, broccoli, and lettuces.

A glycosylglucose formed by an alpha-(1->6)-linkage between D-galactose and D-glucose." []

Pyridoxine, also known vitamin B6, is commonly found in food and is used as a dietary supplement. Pyridoxine is an essential nutrient, meaning the body cannot synthesize it, and it must be obtained from the diet. Sources in the diet include fruit, vegetables, and grain. Although pyridoxine and vitamin B6 are still frequently used as synonyms, especially by medical researchers, this practice is sometimes misleading (PMID: 2192605). Technically, pyridoxine is one of the compounds that can be called vitamin B6 or it is a member of the family of B6 vitamins. Healthy human blood levels of pyridoxine are 2.1 - 21.7 ng/mL. Pyridoxine is readily converted to pyridoxal phosphate which is a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids and aminolevulinic acid. Pyridoxine assists in the balancing of sodium and potassium as well as promoting red blood cell production. Therefore pyridoxine is required by the body to make amino acids, carbohydrates, and lipids. It is linked to cancer immunity and helps fight the formation of homocysteine. It has been suggested that pyridoxine might help children with learning difficulties, and may also prevent dandruff, eczema, and psoriasis. In addition, pyridoxine can help balance hormonal changes in women and aid in immune system. Lack of pyridoxine may cause anemia, nerve damage, seizures, skin problems, and sores in the mouth (Wikipedia). Deficiency of pyridoxine, though rare because of widespread distribution in foods, leads to the development of peripheral neuritis in adults and affects the central nervous system in children (DOSE - 3rd edition). As a supplement pyridoxine is used to treat and prevent pyridoxine deficiency, sideroblastic anaemia, pyridoxine-dependent epilepsy, certain metabolic disorders, problems from isoniazid, and certain types of mushroom poisoning. Pyridoxine in combination with doxylamine is used as a treatment for morning sickness in pregnant women.

A disaccharide formed by a (1<->1)-glycosidic bond between two units of D-glucose." []

L-4-Hydroxyglutamate semialdehyde is an intermediate in Arginine and proline metabolism. L-4-Hydroxyglutamate semialdehyde is the 4th to last step in the synthesis of Glyoxylate and is converted from L-erythro-4-Hydroxyglutamate via the enzyme 1-pyrroline-5-carboxylate dehydrogenase (EC 1.5.1.12). It is then converted to L-1-Pyrroline-3-hydroxy-5-carboxylate via enzymtic reaction.

An N-acylneuraminic acid where the N-acyl group is specified as acetyl." []

Galactinol belongs to the class of organic compounds known as O-glycosyl compounds. These are glycoside in which a sugar group is bonded through one carbon to another group via an O-glycosidic bond. Galactinol is an extremely weak basic (essentially neutral) compound (based on its pKa). Galactinol is an intermediate in galactose metabolism. Galactinol is the fourth-to-last step in the synthesis of D-galactose and the third-to-last step in the synthesis of D-glucose and D-fructose. Galactinol is converted from UDP-galactose via the enzyme inositol 3-alpha-galactosyltransferase (EC 2.4.1.123). It is then converted into raffinose via the enzyme raffinose synthase (EC 2.4.1.82).

N-Methyl-D-aspartic acid is an amino acid derivative acting as a specific agonist at the NMDA receptor, and therefore mimics the action of the neurotransmitter glutamate on that receptor. In contrast to glutamate, NMDA binds to and regulates the above receptor only, but not other glutamate receptors. NMDA is a water-soluble endogenous metabolite that plays an important role in the neuroendocrine system of species across Animalia (PMID:18096065). It was first synthesized in the 1960s (PMID:14056452). NMDA is an excitotoxin; this trait has applications in behavioural neuroscience research. The body of work utilizing this technique falls under the term "lesion studies." Researchers apply NMDA to specific regions of an (animal) subject's brain or spinal cord and subsequently test for the behaviour of interest, such as operant behaviour. If the behaviour is compromised, it suggests that the destroyed tissue was part of a brain region that made an important contribution to the normal expression of that behaviour. Examples of antagonists of the NMDA receptor are ketamine, amantadine, dextromethorphan (DXM), riluzole, and memantine. They are commonly referred to as NMDA receptor antagonists (PMID:28877137).

Endogenous Metabolite Geigy vol. 3 p. 96

Gluconic acid, also known as D-gluconic acid, D-gluconate or (2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanoic acid (also named dextronic acid), is the C1-oxidized form of D-glucose where the aldehyde group has become oxidized to the corresponding carboxylic acid. Gluconic acid belongs to the class of organic compounds known as sugar acids and derivatives. Sugar acids and derivatives are compounds containing a saccharide unit which bears a carboxylic acid group. In aqueous solution, gluconic acid exists in equilibrium with the cyclic ester glucono delta-lactone. Gluconic acid occurs naturally in fruit, honey, kombucha tea and wine. The salts of gluconic acid are known as "gluconates". Gluconic acid, gluconate salts, and gluconate esters occur widely in nature because such species arise from the oxidation of glucose. Gluconic acid exists in all living species, ranging from bacteria to plants to humans. The metabolism of gluconate is well characterized in prokaryotes where it is known to be degraded following phosphorylation by gluconokinase. Glucokinase activity has also been detected in mammals, including humans (PMID: 24896608). Gluconic acid is produced in the gluconate shunt pathway. In the gluconate shunt, glucose is oxidized by glucose dehydrogenase (also called glucose oxidase) to furnish gluconate, the form in which D-gluconic acid is present at physiological pH. Subsequently, gluconate is phosphorylated by the action of gluconate kinase to produce 6-phosphogluconate, which is the second intermediate of the pentose phosphate pathway. This gluconate shunt is mainly found in plants, algae, cyanobacteria and some bacteria, which all use the Entner–Doudoroff pathway to degrade glucose or gluconate; this generates 2-keto-3-deoxygluconate-6-phosphate, which is then cleaved to generate pyruvate and glyceraldehyde 3-phosphate. Glucose dehydrogenase and gluconate kinase activities are also present in mammals, fission yeast, and flies. Gluconic acid has many industrial uses. It is used as a drug as part of electrolyte supplementation in total parenteral nutrition. It is also used in cleaning products where it helps cleaning up mineral deposits. Gluconic acid or Gluconic acid is used to maintain the cation-anion balance on electrolyte solutions. In humans, gluconic acid is involved in the metabolic disorder called the transaldolase deficiency. Gluconic acid has been found to be a metabolite in Aspergillus (Hugo Vanden Bossche, D.W.R. Mackenzie and G. Cauwenbergh. Aspergillus and Aspergillosis, 1987).

L-2-Amino-5-hydroxypentanoic acid is found in pulses. L-2-Amino-5-hydroxypentanoic acid is present in jack bean seeds (Canavalia ensiformis

Fructose is a levorotatory monosaccharide and an isomer of glucose. Although fructose is a hexose (6 carbon sugar), it generally exists as a 5-member hemiketal ring (a furanose)." []

Adenosine monophosphate, also known as 5'-adenylic acid and abbreviated AMP, is a nucleotide that is found in RNA. It is an ester of phosphoric acid with the nucleoside adenosine. AMP consists of the phosphate group, the pentose sugar ribose, and the nucleobase adenine. AMP can be produced during ATP synthesis by the enzyme adenylate kinase. AMP has recently been approved as a 'Bitter Blocker' additive to foodstuffs. When AMP is added to bitter foods or foods with a bitter aftertaste it makes them seem 'sweeter'. This potentially makes lower calorie food products more palatable.

Keto-D-sorbose is a D-sorbose. It is an enantiomer of a keto-L-sorbose. D-sorbose is a natural product found in Sparganium stoloniferum with data available. A ketose sugar that is commonly used in the commercial synthesis of ASCORBIC ACID.

alpha-D-Glucose, also known as alpha-dextrose or alpha-D-GLC, belongs to the class of organic compounds known as hexoses. These are monosaccharides in which the sugar unit is a is a six-carbon containing moeity. alpha-D-Glucose exists in all living species, ranging from bacteria to humans. Outside of the human body, alpha-D-Glucose has been detected, but not quantified in several different foods, such as lemon grass, sourdoughs, mixed nuts, sweet rowanberries, and ginsengs. This could make alpha-D-glucose a potential biomarker for the consumption of these foods. D-Glucopyranose having alpha-configuration at the anomeric centre.

Trehalose, also known as mycose, is a 1-alpha (disaccharide) sugar found extensively but not abundantly in nature. It is thought to be implicated in anhydrobiosis - the ability of plants and animals to withstand prolonged periods of desiccation. The sugar is thought to form a gel phase as cells dehydrate, which prevents disruption of internal cell organelles by effectively splinting them in position. Rehydration then allows normal cellular activity to be resumed without the major, generally lethal damage that would normally follow a dehydration/reyhdration cycle. Trehalose is a non-reducing sugar formed from two glucose units joined by a 1-1 alpha bond giving it the name of alpha-D-glucopyranoglucopyranosyl-1,1-alpha-D-glucopyranoside. The bonding makes trehalose very resistant to acid hydrolysis, and therefore stable in solution at high temperatures even under acidic conditions. The bonding also keeps non-reducing sugars in closed-ring form, such that the aldehyde or ketone end-groups do not bind to the lysine or arginine residues of proteins (a process called glycation). The enzyme trehalase, present but not abundant in most people, breaks it into two glucose molecules, which can then be readily absorbed in the gut. Trehalose is an important components of insects circulating fluid. It acts as a storage form of insect circulating fluid and it is important in respiration. Trehalose has also been found to be a metabolite of Burkholderia, Escherichia and Propionibacterium (PMID:12105274; PMID:25479689) (krishikosh.egranth.ac.in/bitstream/1/84382/1/88571%20P-1257.pdf).

D-Tagatose (CAS: 87-81-0), a rare natural hexoketose, is an isomer of D-galactose. D-Tagatose occurs naturally in Sterculia setigera gum, and it is also found in small quantities in various foods such as sterilized and powdered cow's milk, hot cocoa, and a variety of cheeses, yogurts, and other dairy products. It can be synthesized from D-galactose by isomerization under alkaline conditions in the presence of calcium. D-Tagatose has numerous health benefits, including promotion of weight loss; no glycemic effect; anti-plaque, non-cariogenic, anti-halitosis, prebiotic, and anti-biofilm properties; organ transplants; enhancement of flavor; improvement of pregnancy and fetal development; obesity treatment; and reduction in symptoms associated with type 2 diabetes, hyperglycemia, anemia, and hemophilia (PMID:17492284).

1-AMINOCYCLOBUTANE CARBOXYLIC ACID is a L-alpha-amino acid.