Ketoglutaric add

Bromocresol purple (5.2...6.8) glutamic and ketoglutaric adds [217], halide and halate anions [91,218,219] preservatives [220,221] products of pyrolysis of epoxy resins [222] 5-aminodibenzocyclo-heptane derivatives [223] phenylalkanolamines, eph-edrine [224]... 

Thermal polylysine catalyzes the formation of glutamic acid from a-ketoglutaric add with urea and Cu2+ 24). A reaction mixture of CuS04, urea, a-ketoglutaric acid (0.1 mM each) and 10 mg of proteinoid in 6 ml of pH 7.0 buffer is incubated at 37.5 °C for 24 hours. The glutamic acid formed in the reaction mixture was identified on an amino acid analyzer after desalting on an ion-exchange column 24>. 

Thermal polylysine also catalyzes the formation of a-ketoglutaric acid from glutamic acid with CuCl25). A reaction mixture of lysine-rich proteinoid (20 mg), 14C(U)-l-glutamate (0.1 mM), and CuCl (0.1 mM) in 6 ml of Britton-Robinson buffer (pH 7.0) is incubated at 37.5 °C for 2 hours. More than 40 % of the radioactivity used is recorded in a-ketoglutaric add by paperchromatography of the reaction mixture25 . Free lysine and Leuehs poly-L-lysine have no activity 2S). The reaction obeys Michaelis-Menten kinetics at optimum pH 7.0 25). 

Shiio, I., Otsuka, S., and Tsunoda, T. (1959) Glutamic add formation from glucose by bacteria. II. Glutamic acid and a-ketoglutaric add formation by Brevibacterium flavum No. 2247. /. Biochem., 46 (12), 1597-1605. 

Apparently the entry of citric acid into the scheme can be explained by the conversion of citrate into a-ketoglutarate under the action of a citric dehydrogenase. But an examination of the formulas of citric acid and a-ketoglutaric add shows that dtric dehydrogenase cannot convert the first into the second in one step. 

The succinyl-CoA condenses with glycine, at the a-carbon atom, to form a-amino-j8-ketoadipic acid which is then decarboxylated to S-amino-levulinic acid. The latter is deaminated to ketoglutaraldehyde which is oxidized to ketoglutaric add. This compound enters the tricarboxylic acid cycle or is decarboxylated to succinic acid. In one revolution of the cycle one molecule of glycine is completely oxidized to CO, and water. 

This procea for the fixation of COg is very important. Two examples are, fixation by pyruvic acid to form oxaloacetic acid, and fixation of COg by a-ketoglutaric add. The former is the mechanism for the synthesis of dicarboxyUc acids and the latter for the synthesis of tricarboxylic adds. 

The chief source of glutamic add is a-ketoglutaric add produced in the Krebs cycle. This add can itself only arise in the oxidative decarboxylation of isocitric acid, for the decarboxylation of a-ketoglutarate to give succinate is irreversible. This is the sole pathway for the formation of glutamic add from carbohydrate. 

The amino group is derived from ammonia fixed to a-ketoglutaric add by glutamic dehydrogenase, or from the amino group of another amino add, transferred by transamination. 

Tabaka K, Kimura K, Yamaguchi Y (1969) Process for producing L-glutamic add and a-ketoglutaric add. US Patent 3450599, Kyowa Hakko Kogyo, Tokyo Tongwen X, Weihua Y (2002) Citric acid production by electrodialysis with bipolar membranes. Chem Eng Process 41(6) 519-524... 

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