Carboxylic acids 2-Oxoglutaric acid

Also, the carboxylation of oxoglutaric acid to form isocitric acid catalyzed by isocitric acid dehydrogenase (ICDH) can be driven electrochemically using methyl viologen as mediator without reduced pyridine nucleotides as cofactors. Thus, electrolysis at — 0.95 V vs SCE of a 0.2 M tris buffer solution (pH 7.7)... 

Fig. 20. Electroenzymatic carboxylation of oxoglutaric acid with isocitric acid dehydrogenase (ICDH) using ferredoxin (Fd) as mediator and poly-L-lysine as promoter... 

The thallium benzoate and thallium 2-oxocarboxylates are available via the reaction of thallium acetate with benzoic acid or the 2-oxocarboxylic acids, due to the lower values of these acids (benzoic acid 4.22, benzoylformic acid 1.2, 2-oxoglutaric acid 31/5.14, pyruvic acid 2.49) compared to acetic acid (4.76) (167). The free acetic acid is distilled off with water as an azeotrope and the thallium carboxylates are obtained in high purity. 

Lysine is not only a constituent of proteins. It can also be trimethylated and converted to carnitine (p. 944). In mammals some specific lysyl side chains of proteins undergo N-trimethylation and proteolytic degradation with release of free trimethyllysine (Eq. 24-30) 278/279 The free trimethyllysine then undergoes hydroxylation by a 2-oxoglutarate-Fe2+-ascorbate-dependent hydroxylase (Eq. 18-51) to form P-hydroxytrimethyllysine, which is cleaved by a PLP-dependent enzyme (Chapter 14). The resulting aldehyde is oxidized to the carboxylic acid and is converted by a second 2-oxoglutarate-Fe2+-ascorbate-dependent hydroxylase to carnitine (Eq. 24-30 see also Eq. 18-50). 

CjiHioOs, Mr 222.20, mp. 135-137 °C. An intermediate in the biosynthesis of 1,4-dihydroxynaphthalene-2-carboxylic acid, which in turn is a precursor of alizarin(e), menaquinone (vitamin K3), and vitamin K] (phylloquinone). The biosynthesis proceeds from isochorismic acid and 2-oxoglutaric acid. 

The acidic amino acids, aspartic acid and glutamic acid, represent the aminated forms of oxaloacetic and a-oxoglutaric acids respectively and have two carboxyl groups but only one amino group. Like other amino acids, when they are present in peptide chains the amino group... 

Carboxyethylquinoxalinol and 3-carboxypropylquinoxalinol, formed from 2-oxoglutaric and 2-oxoadipic acids respectively, are reported to be stable to decarboxylation (Langenbeck et aL, 1975), and the derivatives form a useful group of compounds for the determination of most 2-oxocarboxylic acids. However, other carboxylic acids cannot be determined simultaneously as is usual when oxime and substituted oxime derivatives (Section 3.2.1) are used, although it may be advantageous occasionally to determine the 2-oxo acids separately in this way. 

Three modifications of the conventional oxidative citric acid cycle are needed, which substitute irreversible enzyme steps. Succinate dehydrogenase is replaced by fumarate reductase, 2-oxoglutarate dehydrogenase by ferredoxin-dependent 2-oxoglutarate oxidoreductase (2-oxoglutarate synthase), and citrate synthase by ATP-citrate lyase [3, 16] it should be noted that the carboxylases of the cycle catalyze the reductive carboxylation reactions. There are variants of the ATP-driven cleavage of citrate as well as of isocitrate formation [7]. The reductive citric acid... 

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