Glutamine reactions

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. 

The regulation of PRA synthesis from PRPP and glutamine (reaction 1) and PRPP and anmonia (reaction 2) was examined in cell-free preparations of human lymphocytes. ... 

Factor XIII. Factor XIII circulates in the blood as a zymogen composed of two pairs of different polypeptide chains designated A and B. Inert Factor XIII has a molecular weight of 350,000 daltons and is converted to its active transglutaminase form in the presence of thrombin and calcium. Activated Factor XIII, Xllla, induces an irreversible amide exchange reaction between the y-glutamine and S-lysine side chains of adjacent fibrin... 

A mixture of 37.6 g of N-acetyl-L-glutamine and 1.000 ml of water is heated to 40°C, and 900 ml of an isopropanol solution containing 40 g of aluminum isopropoxide isadded to the warm mixture with stirring. The stirring is continued for 10 minutes. The reaction mixture is filtered and the filtrate is concentrated under reduced pressure. Isopropanol is added to the aqueous solution and the salt precipitates in the solution. The precipitates are collected by filtration and upon drying, 48.5 g of the crystalline-like aluminum salt of N-acetyl-L-glutamine are obtained. 

Ammonia is accepted by glutamic acid in an energy (ATP consuming) step, and converted to glutamine. This reaction is catalysed by glutamate synthetase (GS) and can be written as ... 

An alternative to modifying the functional group attached to fibrils is to utilise the chemistry present in the amino acid side chains. Furthermore, as peptides often undergo specific modification by enzymes in vivo, these could be harnessed for synthetic purposes. Qll (Ac-QQKFQFQFEQQ-Am, a fibril-forming peptide based on Pi 1-2), was coupled to lysine-based molecules by treatment with an enzyme (tissue transglutaminase, TGase) which results in a reaction between lysine and glutamine side chains [72] (Fig. 32). 

Figure 28-4. The asparagine synthetase reaction. Note similarities to and differences from the glutamine synthetase reaction (Figure 28-2).

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. 

Figure 29-7. The glutamine synthase reaction strongly favors glutamine synthesis.

Condensation of CO2, ammonia, and ATP to form carbamoyl phosphate is catalyzed by mitochondrial carbamoyl phosphate synthase I (reaction 1, Figure 29-9). A cytosolic form of this enzyme, carbamoyl phosphate synthase II, uses glutamine rather than ammonia as the nitrogen donor and functions in pyrimidine biosynthesis (see Chapter 34). Carbamoyl phosphate synthase I, the rate-hmiting enzyme of the urea cycle, is active only in the presence of its allosteric activator JV-acetylglutamate, which enhances the affinity of the synthase for ATP. Formation of carbamoyl phosphate requires 2 mol of ATP, one of which serves as a phosphate donor. Conversion of the second ATP to AMP and pyrophosphate, coupled to the hydrolysis of pyrophosphate to orthophosphate, provides the driving... 

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. 

Several reactions of IMP biosynthesis require folate derivatives and glutamine. Consequently, antifolate drugs and glutamine analogs inhibit purine biosynthesis. 

For example, the amino acid glutamine is synthesized in cells by the reaction of ammonia with another amino acid, glutamic acid ... 

Figure 4.4 Release of amino acids from cortical slices exposed to 50 mM K+. Measurements by HPEC and fluorescence detection after reaction of amino acids with o-phthalaldehyde 1, aspartate 2, glutamate 3, asparagine 4, serine 5, glutamine 6, histidine 7, homoserine (internal standard) 8, glycine 9, threonine 10, arginine 11, taurine 12, alanine 13, GABA 14, tyrosine. Glutamate concentration is almost 1 pmol/gl which represents a release rate of 30 pmol/min/mg tissue...

The tertiary structure of glutamate racemase has already been resolved and it has also been shown that a substrate analog glutamine binds between two cysteine residues. These data enabled us to predict that the new proton-donating amino acid residue should be introduced at position 74 instead of Gly for the inversion of enantioselectivity of the decarboxylation reaction. 

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