Of glutamic acid

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)... 

Equation 1 has AG° = +14 kJ and is endergonic The mam reason for this is that one of the very stable carboxylate groups of glutamic acid is converted to a less stable amide function... 

The 7 glutamyl phosphate formed m this step is a mixed anhydride of glutamic acid and phosphoric acid It is activated toward nucleophilic acyl substitution and gives glutamine when attacked by ammonia... 

Crystallization Method. Such methods as mechanical separation, preferential crystallisation, and substitution crystallisation procedures are included in this category. The preferential crystallisation method is the most popular. The general procedure is to inoculate a saturated solution of the racemic mixture with a seed of the desired enantiomer. Resolutions by this method have been reported for histidine (43), glutamic acid (44), DOPA (45), threonine (46), A/-acetyl phenylalanine (47), and others. In the case of glutamic acid, the method had been used for industrial manufacture (48). 

The a-carbon of glutamic acid is chiral. A convenient and effective means to determine the chemical purity of MSG is measurement of its specific rotation. The specific optical rotation of a solution of 10 g MSG in 100 mL of 2 A/HQ is +25.16. Besides L-glutamic acid [56-86-0] D-glutamic acid [6893-26-1] and the racemic mixture, DL-glutamic acid [617-65-2] are known. Unique taste modifying characteristics are possessed only by the L-form. 

Certain amino acids and their derivatives, although not found in proteins, nonetheless are biochemically important. A few of the more notable examples are shown in Figure 4.5. y-Aminobutyric acid, or GABA, is produced by the decarboxylation of glutamic acid and is a potent neurotransmitter. Histamine, which is synthesized by decarboxylation of histidine, and serotonin, which is derived from tryptophan, similarly function as neurotransmitters and regulators. /3-Alanine is found in nature in the peptides carnosine and anserine and is a component of pantothenic acid (a vitamin), which is a part of coenzyme A. Epinephrine (also known as adrenaline), derived from tyrosine, is an important hormone. Penicillamine is a constituent of the penicillin antibiotics. Ornithine, betaine, homocysteine, and homoserine are important metabolic intermediates. Citrulline is the immediate precursor of arginine. 

Calculate the pH at which the y-carboxyl group of glutamic acid is two-thirds dissociated. 

The glutarimide best known to the lay public, thalidomide (40), owes its reputation not to efficacy, but to the wholly unanticipated and tragic teratogenic effects elicited by this compound. It might be noted that the very efficacy and lack of the usual barbiturate side effects shown by this drug led to its prescription as a hypnotic for expectant mothers. Condensation of the phthalimide of glutamic acid (39) with ammonia at elevated... 

Mention should also be made of glutamic acid and invert sugar which are used in foodstuffs and demand the use of hydrochloric acid-resistant material in manufacture, and of the essential flavouring oils which should preferably be stored and prepared in stainless steel and aluminium equipment. 

Examining the mass spectrum of glutamic acid-TBDMS shows two high-mass ions that are 28 mass units apart (see Figure 9.3). By adding 57 (C4H9) Daltons to the m/z 432 ion, the MW of the... 

Ward and Mason157) explain these effects by direct hydrogen bonds between the hydroxy group of hydroxyproline in position 3 and the carboxylic side chain of glutamic acid in the adjacent chains. From the sequence we know that in the case of parallel and... 

Glutamic acid is a component of many proteins, such as those in dairy products, meat, legumes, and mushrooms. However, only the free form of glutamic acid or glutamates has an effect on the glutamate receptors. When bound to other amino acids in a protein, it does not stimulate glutamate receptors. 

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]. 

Sidechain conservatism may be split up into at least two kinds 1) substitutions which conserve sidechain bonding forces - providing similar electrostatic, hydrophilic, or hydrogen bonding interactions, and 2) substitutions conserving secondary structure propensity. For instance, substitution of glutamic acid with aspartic acid conserves charge, but this could have a considerable effect upon the secondary structure propensity of the peptide. 

Next, an ammonia moiecuie reacts with the phosphorylated form of glutamic acid, producing phosphoric acid and giutamine ... 

Asada, H, Kawamura, Y, Maruyama, K, Kume, H, Ding, RG, Kanbara, N, Kuzume, H, Sanbo, M, Yagi, T and Obata, K (1997) Cleft palate and decreased brain y-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase. Proc. Natl. Acad. Sci. USA 94 6496-6499. 

The reaction mechanism for glutamate racemase has been studied extensively. It has been proposed that the key for the racemization activity is that the two cysteine residues of the enzyme are located on both sides of the substrate bound to the active site. Thus, one cysteine residue abstracts the a-proton from the substrate, while the other detivers a proton from the opposite side of the intermediate enolate of the amino acid. In this way, the racemase catalyzes the racemization of glutamic acid via a so-called two-base mechanism (Fig. 15). 

R=Me or COOEt) failed.2-Amino-4-phosphonobutanoic acid, the phosphonic acid analogue of glutamic acid, has been obtained in resolved forms by the action of papain, followed by aniline, on 2-benzoylamino-4-(diethoxyphosphinyl)butanoic acid when anilide occurs preferentially for the L- compound. Enantiomers of 4-amino-4-phosphonobutanoic acid were obtained by resolution... 

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