2-Oxoglutaric acid production

The second function, and the one pertinent to this section, is the decarboxylation of oxalosuccinic acid to 2-oxoglutaric acid. This is simply a biochemical example of the ready decarboxylation of a P-ketoacid, involving an intramolecular hydrogen-bonded system. This reaction could occur chemically without an enzyme, but it is known that isocitric acid, the product of the dehydrogenation, is still bound to the enzyme isocitrate dehydrogenase when decarboxylation occurs. 

The reaction of alloxane hydrate (342) and 46a,c gives 100% yield of the products 343a,c upon milling at room temperature [104]. The solid-state reaction of 2-oxoglutaric acid (344) and 46a similarly gives a quantitative yield of the quinoxalinone 345 in the solid state upon heating of coground mixtures for 30 min to 120-125 °C [104]. 

The other product of reaction (35) is a keto acid, whose further fate depends on the exact nature of the R-group in it. Reactions of the type of (34) are catalysed by amino acid Oxidases. The second reaction (35) is spontaneous and requires no enzyme. The most important of the amino acid oxidases is glutamic dehydrogenase, which converts glutamic into a-oxoglutaric acid (generating NADH2 in the process) (36) ... 

Phylloquinone and menaquinone are derived from chorismic acid, which results from 3-phosphoenolpyruvic acid (a product of glycolysis) and D-erythrose 4-phosphate (a product of the pentose and Calvin cycles) as a starting compound for the biosynthesis of phenylalanine, tyrosine and tryptophan. It is transformed into iso-chorismic acid other carbon atoms are derived from 2-oxoglutaric acid. The side chain is provided by ph)4yl diphosphate or by polyprenyl diphosphates, which are formed from geranylgeranyl diphosphate. The final reaction is a methylation at C-2. 

Pyruvic acid and 2-oxoglutaric acid (formerly a-ketoglutaric acid) are generally present in wine (Table 8.5). They are secondary products of alcoholic fermentation. Considering their low K value, they can play an important role in the SO2 combination rate. For example, a wine containing 200 mg of pyruvic acid aud 100 mg of 2-oxoglutaric acid per liter has 93 mg of SO2 per liter bound to these acids for 20 mg of free SO2. 

Relationship between Enzyme Activity of the 2-Oxoglutarate Dehydrogenase Complex and Glutamic Acid Production... 

Figure 11.5 Metabolic pathways related to glutamic acid production in C glutamicum. ICDH, isocitrate dehydrogenase, ODHC, 2-oxoglutarate dehydrogenase complex GDH, glutamate dehydrogenase PPC, phosphoenolpyruvate carboxylase and PC, pyruvate carboxylase.

AcCoA is the building block of fatty acids, polyketides, and mevalonic acid (MVA), a cytosolic precursor of the C5 isoprene units for the biosynthesis of terpenes in the C,5 and Cj series (mind it is different from the MEP pathway, in product, and in cell location). Finally, AcCoA enters the citric acid or Krebs cycle, which leads to several precursors of amino acids. These are oxaloacetic acid, precursor of aspartic acid through transamination (thus toward lysine as a nitrogenated C N linear unit and methionine as a methyl supplier), and 2-oxoglutaric acid, precursor of glutamic acid (and subsequent derivatives such as ornithine as a nitrogenated C N linear unit). All these amino acids are key precursors in the biosynthesis of many alkaloids. 

On heating the parent acid of ester VI (from condensation of D-glucose with diethyl 3-oxoglutarate) in aqueous solution,11 following the procedure employed to obtain the corresponding derivative of ethyl acetoacetate XXVI, a sirup results. However, its change in optical activity shows a parallelism with that in analogous cases where crystalline products are isolated, and apparently indicates anhydride formation (see the last line in Table V). 

We should note at this point that the TCA cycle is more than just a means of producing NADH for oxidative phosphorylation. The pathway also provides a number of useful intermediates for other, often synthetic, pathways. For example, citrate is the starting substance for fat synthesis (Chapter 9) succinyl-CoA is required for haem production and 2-oxoglutarate and oxaloacetate in particular are involved with amino acid and pyrimidine metabolism. Pathways which have dual catabolic/anabolic functions are referred to as amphibolic . 

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