数据之源，洞见之始

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.

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).

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.

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.

HON is a L-alpha-amino acid. 5-Hydroxy-4-oxonorvaline is a natural product found in Streptomyces akiyoshiensis with data available.

A member of the class of oxindoles that is oxindole (1,3-dihydro-2H-indol-2-one) in which one of the hydrogens at position 3 has been replaced by a methyl group." []

This compound belongs to the family of Benzyl Cyanides. These are organic compounds containing an acetonitrile with one hydrogen replaced by a phenyl group

3-Hydroxy-2-oxoindole is an oxidized indole derivative. Indoles are compounds containing an indole moiety, which consists of pyrrole ring fused to benzene to form 2,3-benzopyrrole. 3-hydroxy-2-oxoindole is a naturally occurring indole metabolite found in human urine (PMID: 11722560). It is a reduced form of the more abundant naturally occurring indole metabolite known as isatin (which is derived from the gut microbial metabolism of tryptophan). 3-hydroxy-2-oxoindole is generated via the activity of the enzyme known as isatin reductase, which is found in the liver and kidney (PMID: 11722560). It exhibits modest monoamine oxidase A and B inhibitory activity.

A 1,5-dicarboxylic acid compound having a 3-amino substituent. It has been isolated from the extracts of the algae, Chondria armata." []

5,6-Dihydroxyindole is a substrate for Tyrosinase.

2,3-dihydroxyindole is a dihydroxyindole.

Putative proline-derived Maillard product formed in model reactions with proline or pyrroline and ascorbic acid.

Putative proline-derived Maillard product formed in model reactions with proline and ascorbic acid.

5-methoxyindole is a member of indoles.

1-(2-Furanylmethyl)-1H-pyrrole is found in alcoholic beverages. 1-(2-Furanylmethyl)-1H-pyrrole is one of the constits. of the aroma of coffee also present in bread, roasted almond, popcorn, malt, roasted chicken, beer and sandalwood oil. 1-(2-Furanylmethyl)-1H-pyrrole is a flavour ingredien

This compound belongs to the family of Short-chain Keto Acids and Derivatives. These are keto acids with an alkyl chain the contains less than 6 carbon atoms

7-Methyl-6,7-dihydrocyclopenta[c]pyridin-5-one has been reported in Harpagophytum zeyheri with data available.

Fagomine is an alkaloid found in the seeds of Castanospermum australe (commonly known as the Black Bean or the Moreton Bay Chestnut) (PMID: 25583438). Castanospermum australe is a large evergreen tree of the legume family native to the east coast of Australia in Queensland and New South Wales, and to the Pacific islands of Vanuatu, New Caledonia, and the island of New Britain (Papua New Guinea). The seeds are poisonous, but become edible when carefully prepared by roasting, cutting up into small pieces, leaching with running water for several days, and pounding into flour (Wikipedia).

N,n-dimethylanthranilic acid is a member of the class of compounds known as aminobenzoic acids. Aminobenzoic acids are benzoic acids containing an amine group attached to the benzene moiety. N,n-dimethylanthranilic acid is soluble (in water) and a weakly acidic compound (based on its pKa). N,n-dimethylanthranilic acid can be found in fig, which makes n,n-dimethylanthranilic acid a potential biomarker for the consumption of this food product.

A member of the class of hydroxypiperidines that is piperidine carrying a hydroxymethyl substituent at position 2 as well as two hydroxy substituents at positions 3 and 4 (the 2R,3R,4S-diastereomer)." []

3,4-Pyrrolidinediol, 2-(hydroxymethyl)-1-methyl-, (2R,3R,4R)- is a natural product found in Angylocalyx pynaertii with data available. A very potent liver carcinogen.

p-Synephrine is an endogenous amine in plasma, in variable levels with a tendency to be higher in hypertensive patients (PMID 8255371).

Daunosamine is a hexosamine and a trideoxyhexose derivative. Daunosamine is a natural product found in Streptomyces peucetius with data available.

NAPQI is a metabolite of acetaminophen. NAPQI (N-acetyl-p-benzoquinone imine) is a toxic byproduct produced during the xenobiotic metabolism of the analgesic paracetamol (acetaminophen). It is normally produced only in small amounts, and then almost immediately detoxified in the liver. However, under some conditions in which NAPQI is not effectively detoxified (usually in case of paracetamol overdose), it causes severe damage to the liver. (Wikipedia)