Glutamate metabolism, pathways

Although the GOGAT reaction consumes one NADPH it produces two molecules of glutamate that can yield, via GDH, two NADPH that can in turn serve as an electron source for the anti-oxidative enzymes glutathione reductase (GR) and thioredoxin reductase (TrxR see p. 264-266) glutamine could also be used in pyrimidine biosynthesis. (The glutamate metabolic pathway can be found online at http //sites.huji.ac. il/malaria/maps/glutamatemetpath.html last accessed 16 July 2008.)... 

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. 

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

Gibbs M. E. and Hertz L. (2005). Importance of glutamate-generating metabolic pathways for memory consolidation in chicks. J. Neurosci. Res. 81 293-300. 

Figure 11 Nitrogen sources and metabolic pathways in marine phytoplankton. Solid circles are transporters. Boxes are the catalytic enzymes and open circles are metals associated with each enzyme. Ur, Urease NR, Nitrate Reductase NiR, Nitrite Reductase AAOx, amino acid oxidase AmOx, amine oxidase GS-GOGAT, Glutamine Synthetase- Glutamate oxy-glutarate aminotransferase (or glutamate synthase).

Phenylketonuria (PKU) is an inborn error of metabolism by which the body is unable to convert surplus phenylalanine (PA) to tyrosine for use in the biosynthesis of, for example, thyroxine, adrenaline and noradrenaline. This results from a deficiency in the liver enzyme phenylalanine 4-mono-oxygenase (phenylalanine hydroxylase). A secondary metabolic pathway comes into play in which there is a transamination reaction between PA and a-keto-glutaric acid to produce phenylpyruvic acid (PPVA), a ketone and glutamic acid. Overall, PKU may be defined as a genetic defect in PA metabolism such that there are elevated levels of both PA and PPVA in blood and excessive excretion of PPVA (Fig. 25.7). 

As with glutamic acid production, some modification of the normal metabolic pathway of C. glutamicum imposed by the fermentation conditions, is necessary in order to accumulate lysine in the medium. At present, worldwide production of L-lysine by fermentation routes totals some 70,000 tonnes annually, about 40% of this by Japan. About 9,000 tonnes of racemic lysine (DL mixture) per year is also produced synthetically from petrochemical sources. One interesting synthetic substrate for DL-lysine is caprolactam (or 6-amino-caproic acid), a starting material, which is readily available on a tonnage scale from its use as a nylon monomer. 

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