Glutamic acid pathways

The 20 fflnino acids listed in Table 27.1 are biosynthesized by a number of different pathways, and we will touch on only a few of them in an introductory way. We will examine the biosynthesis of glutamic acid first because it illustrates a biochemical process analogous to a reaction we discussed earlier in the context of amine synthesis, reductive amination (Section 22.10). 

C14-0083. Although the ATP-ADP reaction is the principal energy shuttle in metabolic pathways, many other examples of coupled reactions exist. For example, the glutamic acid-glutamine reaction discussed in the text can couple with the acetyl phosphate reaction shown in Example 14-10. Write the balanced equation for the coupled reaction operating in the direction of overall spontaneity and calculate A G ° for the overall process. 

Akhtar et al. [20] have studied the identification of photoproducts of fohc acid and their degradation pathways in aqueous solution using preparative TLC. An aqueous solution of folic acid irradiated with UV at pH 2.4 to 10.0 for 6 h was subjected to TLC analysis, which gave separation of fohc add (Rj 0.67), p-woi-nobenzolyl-L-glutamic acid (Figure 10.12). The photolyzed solutions were... 

Note that the strength of the correlations is increased by the fact that the citric acid pathway is today isolated in mitochondria derived from a distinct early life form and linked to both aspartate and glutamate, in which A and C are dominant amino-acid carriers, while glycolysis and the pentose shunt are cytoplasmic, where U and G are more dominant amino-acid carriers. 

The first example of a dynamic flux analysis was a study performed in the 1960s [269]. In the yeast Candida utilis, the authors determined metabolic fluxes via the amino acid synthesis network by applying a pulse with 15N-labeled ammonia and chasing the label with unlabeled ammonia. Differential equations were then used to calculate the isotope abundance of intermediates in these pathways, with unknown rate values fitted to experimental data. In this way, the authors could show that only glutamic acid and glutamine-amide receive their nitrogen atoms directly from ammonia, to then pass it on to the other amino acids. 

It interferes with metabolic pathways of amino acids leading from glutamic acid to the citric acid (Krebs) cycle and urea. 

These examples illustrate that biomolecules may act as catalysts in soils to alter the structure of organic contaminants. The exact nature of the reaction may be modified by interaction of the biocatalyst with soil colloids. It is also possible that the catalytic reaction requires a specific mineral-biomolecule combination. Mortland (1984) demonstrated that py ridoxal-5 -phosphate (PLP) catalyzes glutamic acid deamination at 20 °C in the presence of copper-substituted smectite. The proposed pathway for deamination involved formation ofa Schiff base between PLP and glutamic acid, followed by complexation with Cu2+ on the clay surface. Substituted Cu2+ stabilized the Schiff base by chelation of the carboxylate, imine nitrogen, and the phenolic oxygen. In this case, catalysis required combination of the biomolecule with a specific metal-substituted clay. 

The diverse origin of two structurally similar compounds is exemplified by the (3 -lactam antibiotics isopenicillin N (1) and clavulanic acid (2). While these molecules are structurally and functionally similar, they are derived by quite different routes. Isopenicillin N is formed by the direct cyclization of the tripeptide (3) (B-80MI10400) while clavulanic acid appears to be elaborated directly from a three-carbon intermediate of the glycolytic pathway (possibly phosphoenolpyruvate, 4) and glutamic acid (5) (B-80M110401). 

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