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The glutamate/GABA–glutamine cycle is a metabolic pathway that describes the release of either glutamate or GABA from neurons which is then taken up into astrocytes (non-neuronal glial cells). In return, astrocytes release glutamine to be taken up into neurons for use as a precursor to the synthesis of either glutamate or GABA. [2]
The critic acid cycle can then produce 2-oxoglutarate, which can be used to make glutamate, which can in turn be made into GABA, continuing the cycle. [8] GABA is a very important neurotransmitter in animal brains, and a low concentration of GABA in mammalian brains has been linked to several neurological disorders, including Alzheimer's ...
Hydrolysis of the amino group of glutamine yielding glutamate and ammonium. Catalyzing enzyme: glutaminase (EC 3.5.1.2) 2. Glutamate can be excreted or can be further metabolized to α-ketoglutarate. For the conversion of glutamate to α-ketoglutarate three different reactions are possible: Catalyzing enzymes: glutamate dehydrogenase (GlDH), EC ...
Glutamate also serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABA-ergic neurons. This reaction is catalyzed by glutamate decarboxylase (GAD). [ 28 ] GABA-ergic neurons are identified (for research purposes) by revealing its activity (with the autoradiography and immunohistochemistry methods) [ 29 ...
GABA is also the primary inhibitory neurotransmitter in the cerebral cortex and has the highest level of expression within it. [15] The GABA affinity (K m) of the mouse isoform of GAT1 is 8 μM. [16] In the brain of a mature mammal, glutamate is converted to GABA by the enzyme glutamate decarboxylase (GAD) along with the addition of vitamin B6.
Most neurons secrete with glutamate or GABA. Glutamate is excitatory, meaning that the release of glutamate by one cell usually causes adjacent cells to fire an action potential. (Note: Glutamate is chemically identical to the MSG commonly used to flavor food.) GABA is an example of an inhibitory neurotransmitter. Monoamine neurotransmitters:
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Glutamate is synthesized in the central nervous system from glutamine as part of the glutamate–glutamine cycle by the enzyme glutaminase. This can occur in the presynaptic neuron or in neighboring glial cells. Glutamate itself serves as metabolic precursor for the neurotransmitter GABA, via the action of the enzyme glutamate decarboxylase.