Glutamine synthesis and

One example of a naturally occurring diazirine, duazomycin A (137 Scheme 11.20), has been reported, isolated in 1985 from a Streptomyces species during a screen for herbicidal compounds [196], It was fotind to inhibit de novo starch synthesis and it was suggested that this is due to direct inhibition of protein synthesis. Duazomycin A is structurally related to 6-diazo-5-oxo-L-norleucine (138), also reported as a natural product from Streptomyces [197], which acts as a glutamine antagonist and inhibits purine biosynthesis [198],... 

Formation of glutamine is catalyzed by mitochondrial glutamine synthase (Figure 29-7). Since amide bond synthesis is coupled to the hydrolysis of ATP to ADP and P , the reaction strongly favors glutamine synthesis. One function of glutamine is to sequester ammonia in a nontoxic form. 

Hyperammonemia Type 2. A deficiency of ornithine transcarbamoylase (reaction 2, Figure 29-9) produces this X chromosome-linked deficiency. The mothers also exhibit hyperammonemia and an aversion to high-protein foods. Levels of glutamine are elevated in blood, cerebrospinal fluid, and urine, probably due to enhanced glutamine synthesis in response to elevated levels of tissue ammonia. 

Bridging the 40-A gap between glutamine hydrolysis and GIn-tRNA " synthesis 396... 

The rate of synthesis of some amino acids that are normally considered to be indispensable is not sufficient under conditions when the demand for them is increased (e.g. after severe trauma, major surgery or during sepsis). These amino acids include glutamine, cysteine and. 

Figure 21.23 The positions where the nitrogen atoms of glutamine glycine and aspartate are repaired for nucleotide synthesis. Glutamine also gives rise to aspartate via glutaminolysis (Chapter 8). (See Appendix 20.1 and Figure 20.8).

Lydon J, Duke SO, Inhibitots of glutamine synthesis, in Singh BK (ed.). Plant Amino Acids Biochemistry and Biotechnology, Marcel Dekket, New York, pp. 445— 464,1999. 

The synthesis and characterization of water-soluble "random" copolymers containing t-valine with either A -O-hydroxypropyD-L-glutamine or / -(A-hydroxybutyD-L-glutamine are described, and the thermally induced helix-coil transitions of these copolymers in water are studied. The incorporation of /.-valine is found to decrease the helix content of the polymer at low temperatures and increase it at high temperatures. The Zimm-Bragg parameters o and s for the helix-coil transition in poly(t-valine) in water are deduced from an analysis of the melting curves of the copolymers. The values of s, computed for o = 1 x 1CI-4, are s 0.85 (273 K), 0.93 (293 K), 1.00 (313 K), 1.06 (333 Kl. 

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