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|Jmol-3D images||Image 1|
|Molar mass||146.11 g/mol|
|Melting point||115 °C|
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
α-Ketoglutaric acid is one of two ketone derivatives of glutaric acid. (The term "ketoglutaric acid," when not further qualified, almost always refers to the alpha variant. β-Ketoglutaric acid varies only by the position of the ketone functional group, and is much less common.)
α-Ketoglutarate is a key intermediate in the Krebs cycle, coming after isocitrate and before succinyl CoA. Anaplerotic reactions can replenish the cycle at this juncture by synthesizing α-ketoglutarate from transamination of glutamate, or through action of glutamate dehydrogenase on glutamate.
Formation of amino acids
Glutamine is synthesized from glutamate by glutamine synthase, which utilizes an ATP to form glutamyl phosphate; this intermediate is attacked by ammonia as a nucleophile giving glutamine and inorganic phosphate.
Another function is to combine with nitrogen released in the cell, therefore preventing nitrogen overload.
α-Ketoglutarate is one of the most important nitrogen transporters in metabolic pathways. The amino groups of amino acids are attached to it (by transamination) and carried to the liver where the urea cycle takes place.
α-Ketoglutarate is transaminated, along with glutamine, to form the excitatory neurotransmitter glutamate. Glutamate can then be decarboxylated (requiring vitamin B6) into the inhibitory neurotransmitter GABA.
Relationship to molecular oxygen
Acting as a co-substrate, it also plays important function in oxidation reactions involving molecular oxygen.
Molecular oxygen (O2) directly oxidizes many compounds to produce useful products in an organism, such as antibiotics, etc., in reactions catalyzed by oxygenases. In many oxygenases, α-ketoglutarate helps the reaction by being oxidized together with the main substrate. In fact, one of the α-ketoglutarate-dependent oxygenases is an O2 sensor, informing the organism the oxygen level in its environment.
In combination with molecular oxygen, alpha-ketoglutarate is one of the requirements for the hydroxylation of proline to hydroxyproline in the production of Type 1 Collagen.
α-Ketoglutaric acids is sold as a dietary supplement and to body builders as AKG or a-KG with the claim that it improves peak athletic performance. This claim is based on studies that show excess ammonia in the body can combine with alpha-ketoglutarate, reducing problems associated with ammonia toxicity. However, the only studies that show alpha-ketoglutarate can reduce ammonia toxicity have been performed in hemodialysis patients.
α-Ketoglutarate can be produced by:
- Oxidative decarboxylation of isocitrate by isocitrate dehydrogenase;
- Oxidative deamination of glutamate by glutamate dehydrogenase.
Alpha-ketoglutarate can be used to produce:
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles. [§ 1]
- The interactive pathway map can be edited at WikiPathways: "TCACycle_WP78".
|Citric Acid Cycle Metabolic Pathway|
|Acetyl-CoA||NADH + H+||NAD+||H2O||FADH2||FAD||CoA + ATP(GTP)||Pi + ADP(GDP)|
|+||H2O||NADH + H+ + CO2|
|H2O||H2O||NAD(P)+||NAD(P)H + H+||CO2|