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Glutamate is a very major constituent of a wide variety of proteins; consequently it is one of the most abundant amino acids in the human body. [1] Glutamate is formally classified as a non-essential amino acid, because it can be synthesized (in sufficient quantities for health) from α-ketoglutaric acid, which is produced as part of the citric acid cycle by a series of reactions whose ...
Glutamate (the conjugate base of glutamic acid) is abundant in the human body, but particularly in the nervous system and especially prominent in the human brain where it is the body's most prominent neurotransmitter, the brain's main excitatory neurotransmitter, and also the precursor for GABA, the brain's main inhibitory neurotransmitter. [2]
In biochemistry, the glutamate–glutamine cycle is a cyclic metabolic pathway which maintains an adequate supply of the neurotransmitter glutamate in the central nervous system. [1] Neurons are unable to synthesize either the excitatory neurotransmitter glutamate , or the inhibitory GABA from glucose .
Excessive glutamate release can overstimulate the brain and lead to excitotoxicity causing cell death resulting in seizures or strokes. [22] Excitotoxicity has been implicated in certain chronic diseases including ischemic stroke , epilepsy , amyotrophic lateral sclerosis , Alzheimer's disease , Huntington disease , and Parkinson's disease .
Glutamate is also a neurotransmitter (see below), which makes it one of the most abundant molecules in the brain. Malignant brain tumors known as glioma or glioblastoma exploit this phenomenon by using glutamate as an energy source, especially when these tumors become more dependent on glutamate due to mutations in the gene IDH1. [21] [22
Stylized depiction of an activated NMDAR. Glutamate is in the glutamate-binding site and glycine is in the glycine-binding site. The allosteric site, which modulates receptor function when bound to a ligand, is not occupied. NMDARs require the binding of two molecules of glutamate or aspartate and two of glycine [1] [2]
Glutamate is a prime example of an excitotoxin in the brain, and it is also the major excitatory neurotransmitter in the central nervous system of mammals. [14] During normal conditions, glutamate concentration can be increased up to 1mM in the synaptic cleft, which is rapidly decreased in the lapse of milliseconds. [15]
When disturbed, an accumulation of glutamate occurs as a result of a mutation in the glutamate transporters, which act like pumps to clear glutamate from the synapse. This causes glutamate concentration to be several times higher in the blood than in the brain; in turn, the body must act to maintain equilibrium between the two concentrations by ...