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 (‚ÄìNH2) and carboxyl (‚ÄìCOOH) 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.