Glutamic acid reactions

Glutamine is an oi amino acid found in proteins. In mammals, glutamine is a non-essential amino acid, meaning it does not need to be present in the diet. Glutamine is classified as an amide because it is an amide derivative of glutamic acid (Reaction 1 below). Glutamine is a very important compound in transamination reactions. 

Synonyms Glutamic acid, reaction prods, with glucose... 

L-Glutamic acid, N-(l-oxohexadecyl)- Glutamic acid palmitamide. See Palmitoyl glutamic acid Glutamic acid, reaction prods, with glucose. 

Affinity labeling experiments with bromoacetyl compounds are biased by two important limitations, which often make them inferior to comparable photoaffinity labels. The number of properly oriented amino acid functional groups that can undergo a nucleophilic displacement reaction in the active site of a protein is limited to histidine, lysine, tyrosine, cysteine, and glutamic acid. Reactions are strongly influenced by the intrinsic piC of the respective amino acid residue and by the pH of the incubation mixture. It should be noted that bromoacetyl compounds can also react with RNA . The other limitation is that the time point for the affinity labeling reaction to occur cannot be freely chosen. One can only incubate the reactants and let them react for a given time. Reactions are usually quite slow and take considerable time for completion, which can vary between 1 and 20 hr. - ... 

The 20 ammo acids listed m Table 27 1 are biosynthesized by a number of different path ways and we will touch on only a few of them m an introductory way We will exam me the biosynthesis of glutamic acid first because it illustrates a biochemical process analogous to a reaction we discussed earlier m the context of amine synthesis reductive ammatwn (Section 22 10)... 

The reaction is very slow in neutral solution, but the equiUbrium shifts toward the lactam rather than glutamic acid. Under strongly acidic or alkaline conditions, the ring-opening reaction requires a very short time (10). Therefore, neutralization of L-glutamic acid should be performed cautiously because intramolecular dehydration is noticeable even below 190°C. 

The first L-folic acid synthesis was based on the concept of a thiee-component, one-pot reaction (7,22). Ttiainino-4(3JT)-pyrirnidinone [1004-45-7] (10) was reacted simultaneously with C -dibromo aldehyde [5221-17-0] (11) and j )-aminoben2oyl-L-glutamic acid [4271-30-1] (12) to yield fohc acid (1). 

Radiolabeled folate provides a powerful tool for folate bioavaHabiUty studies in animals and for diagnostic procedures in humans. Deuteration at the 3- and 5-positions of the central benzene ring of foHc acid (31) was accompHshed by catalytic debromination (47,48) or acid-cataly2ed exchange reaction (49). Alternatively, deuterium-labeled fohc acid (32) was prepared by condensing pteroic acid with commercially available labeled glutamic acid (50). 

Folic acid is synthesized both in microorganisms and in plants. Guanosine-5-ttiphosphate (GTP) (33), -aminobenzoic acid (PABA), and L-glutamic acid are the precursors. Reviews are available for details (63,64). The sequence of reactions responsible for the enzymatic conversion of GTP to 7,8-dihydrofohc acid (2) is shown. 

In E. coli GTP cyclohydrolase catalyzes the conversion of GTP (33) into 7,8-dihydroneoptetin triphosphate (34) via a three-step sequence. Hydrolysis of the triphosphate group of (34) is achieved by a nonspecific pyrophosphatase to afford dihydroneopterin (35) (65). The free alcohol (36) is obtained by the removal of residual phosphate by an unknown phosphomonoesterase. The dihydroneoptetin undergoes a retro-aldol reaction with the elimination of a hydroxy acetaldehyde moiety. Addition of a pyrophosphate group affords hydroxymethyl-7,8-dihydroptetin pyrophosphate (37). Dihydropteroate synthase catalyzes the condensation of hydroxymethyl-7,8-dihydropteroate pyrophosphate with PABA to furnish 7,8-dihydropteroate (38). Finally, L-glutamic acid is condensed with 7,8-dihydropteroate in the presence of dihydrofolate synthetase. 

The side chains of the 20 different amino acids listed in Panel 1.1 (pp. 6-7) have very different chemical properties and are utilized for a wide variety of biological functions. However, their chemical versatility is not unlimited, and for some functions metal atoms are more suitable and more efficient. Electron-transfer reactions are an important example. Fortunately the side chains of histidine, cysteine, aspartic acid, and glutamic acid are excellent metal ligands, and a fairly large number of proteins have recruited metal atoms as intrinsic parts of their structures among the frequently used metals are iron, zinc, magnesium, and calcium. Several metallo proteins are discussed in detail in later chapters and it suffices here to mention briefly a few examples of iron and zinc proteins. 

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 ... 

The best results were obtained with L-aspartic add as the amino donor for P. denitrificam and phenylpyruvic add as the amino acceptor. With L-aspartic add, conversion of phenylpyruvic add exceeded 90%. This may be attributed to absence of feedback inhibition of the reaction due to metabolism of file reaction product, oxaloacetic add. When using glutamic acid the conversion of phenylpyruvic add did not exceed 60%. 

This reaction requires the formation of an hydroxide ion, as in the enzyme reaction. A proper reference reaction for the first step in the enzyme would then be simply the proton transfer from a water molecule to a glutamic acid in solution ... 

In some cases, the use of a large excess of alcohol is an option to drive the reaction to completion. Alcoholysis of glutamic acid dimethyl ester derivatives with acylase I was regio- and enantioselective (Figure 6.15). An excess of butanol was used as nucleophile and solvent [62]. 

In subsequent experiments (66), this locked substrate was used to obtain evidence for the hypothesis (67) that enzyme-bound y-glutamyl phosphate 14 is an intermediate in the enzyme-catalyzed reaction. All attempts to isolate this acyl phosphate 14 have failed (66), presumably because of the marked tendency of this intermediate to cyclize to pyrrolidonecarboxyUc acid, 15, and to hydrolyze to glutamic acid. 

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