Editing Glutamic acid (section)

=== Metabolism ===
Glutamate is a key compound in cellular [[metabolism]]. In humans, dietary [[proteins]] are broken down by digestion into [[amino acids]], which serve as metabolic fuel for other functional roles in the body. A key process in amino acid degradation is [[transamination]], in which the amino group of an amino acid is transferred to an α-[[Keto acid|ketoacid]], typically catalysed by a [[transaminase]]. The reaction can be generalised as such:

: R<sub>1</sub>-amino acid + R<sub>2</sub>-α-[[Keto acid|ketoacid]] ⇌ R<sub>1</sub>-α-ketoacid + R<sub>2</sub>-amino acid

A very common α-keto acid is [[α-ketoglutarate]], an intermediate in the [[citric acid cycle]]. Transamination of α-ketoglutarate gives glutamate. The resulting α-ketoacid product is often a useful one as well, which can contribute as fuel or as a substrate for further metabolism processes. Examples are as follows:

: [[alanine]] + α-ketoglutarate ⇌ [[pyruvate]] + glutamate

: [[aspartate]] + α-ketoglutarate ⇌ [[oxaloacetate]] + glutamate

Both [[pyruvate]] and [[oxaloacetate]] are key components of cellular metabolism, contributing as substrates or intermediates in fundamental processes such as [[glycolysis]], [[gluconeogenesis]], and the [[citric acid cycle]].

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]],<ref name="springerlink" /> as follows:

: glutamate + H<sub>2</sub>O + [[Nicotinamide adenine dinucleotide phosphate|NADP]]<sup>+</sup> → α-ketoglutarate + [[Nicotinamide adenine dinucleotide phosphate|NADPH]] + NH<sub>3</sub> + H<sup>+</sup>

Ammonia (as [[ammonium]]) is then excreted predominantly as [[urea]], synthesised in the [[liver]]. Transamination can thus be linked to deamination, effectively allowing nitrogen from the amine groups of amino acids to be removed, via glutamate as an intermediate, and finally excreted from the body in the form of urea.

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]].<ref>{{cite journal|last1=van Lith|first1=SA|last2=Navis|first2=AC|last3=Verrijp|first3=K|last4=Niclou|first4=SP|last5=Bjerkvig|first5=R|last6=Wesseling|first6=P|last7=Tops|first7=B|last8=Molenaar|first8=R|last9=van Noorden|first9=CJ|last10=Leenders|first10=WP|title=Glutamate as chemotactic fuel for diffuse glioma cells: are they glutamate suckers?|journal=Biochimica et Biophysica Acta (BBA) - Reviews on Cancer|date=August 2014|volume=1846|issue=1|pages=66–74|pmid=24747768|doi=10.1016/j.bbcan.2014.04.004|url=https://orbilu.uni.lu/handle/10993/60245 }}</ref><ref>{{cite journal|last1=van Lith|first1=SA|last2=Molenaar|first2=R|last3=van Noorden|first3=CJ|last4=Leenders|first4=WP|title=Tumor cells in search for glutamate: an alternative explanation for increased invasiveness of IDH1 mutant gliomas|journal=Neuro-Oncology|date=December 2014|volume=16|issue=12|pages=1669–1670|pmid=25074540|doi=10.1093/neuonc/nou152|pmc=4232089}}</ref>

{{see also|Glutamate–glutamine cycle}}