7,-Glutamic acid

A cyclic, internal amide derivative of glutamic acid is pyrrolidone carboxylic acid (also known as pyroglu-tamic acid or 2-oxoproline). Some proteins (e.g., heavy chains of immunoglobulins Chapter 35) and peptides (e.g., thyrotropin-releasing hormone Chapter 33) have py-roglutamic acid as their N-terminal amino acid residue. 

Acrylnitrile is catalytically formylated with CO/H2 and the resultant aldehyde is transformed through a Strecker reaction into glutamic acid dinitrile which yields D,L-glutamic acid after alkaline hydrolysis. Separation of the racemate is achieved by preferential crystallization of the L-form from an oversaturated solution after seeding with L-glutamic acid  

A fermentation procedure with various selected strains of microorganisms (Brevibacterium flavum, Brev. roseum, Brev. saccharolyticum) provides L-glutamic acid in yields of 50 g/l of fermentation liquid  

Separation of isomers is done at the a-amino caprolactam (Acl) step through the sparingly soluble salt of the L-component with L-pyrrolidone carboxylic acid (Pyg)  

The wet gluten (about 1300 g. ) is placed (Note 3) in a 5-I. round-bottom flask and covered with 1600 cc. of concentrated hydrochloric acid (sp. gr. 1.19). This reaction mixture is then warmed on the steam bath until the purple color disappears (about two hours). A reflux condenser is then attached and the solution is boiled gently over a flame for about eighteen hours. The hot solution is filtered with suction (Note 4) and the black residue of melanin is washed with about 200 cc. of water. The combined filtrate and washings are concentrated under reduced pressure until the volume is reduced to about 1500 cc. This solution is allowed to cool to room temperature and the crystals of glutamic acid hydrochloride filtered and washed with two 30-cc. portions of 95 per cent ethyl alcohol saturated with hydrogen chloride. The washings are discarded (Note 5) and the 

In order to obtain free glutamic acid, 183 g. (1 mole) of the above hydrochloride is dissolved in 750 cc. of distilled water and treated with 500 cc. of 2 N sodium carbonate solution. After standing over night, the free acid which has crystallized is filtered and washed with ice water until free of sodium chloride. The mother liquor and washings are united and concentrated to 300-350 cc. and again allowed to stand over night. The crystals so obtained are filtered and washed with ice-water. The total yield of colorless crystals which melt at 197-198° (corr.) is 109-120 g. (74-82 per cent of the theoretical amount). 

The yield of glutamic acid hydrochloride varies somewhat with the brand of flour. The results described in this procedure were obtained with Gold Medal flour. 

The water should have a temperatue of 20-25° in order to avoid unduly chilling the hands. Instead of washing the starch out of the gluten as described in the procedure, it is sometimes found convenient to place the flour in a muslin sack and wash the starch out through the meshes. This procedure usually requires a somewhat longer time. 

The gluten is best introduced by first replacing all the air in the flask by steam, and then allowing the suction caused by the condensation of the steam to draw in the mass in one portion. 

Department of Bioinformatic Engineering, Graduate Schooi of information Science and 

1 Triggers for Glutamic Acid Overproduction in Corynebacterium Glutamicum 

2 Metabolic Change and Its Molecular Mechanism During Glutamic Acid Production by Corynebacterium Glutamicmn 

1 Metabolic Flux Redistribution by the Induction of Glutamic Acid Production in Corynebacterium Glutamicum 

2 The Importance of Anaplerotic Reactions in Glutamic Acid Production by Corynebacterium Glutamicum 

---

MSG, C8H8NNa04,H20. Flavouring agent extensively used as a food additive. Prepared from natural or synthetic L-glutamic acid. 

The data led to tire cycle shown in figure C2.7.8. Here, only tire active site on tire interior enzyme surface (section C2.6) is depicted, consisting of R groups including aspartic acid, glutamic acid and otliers, represented witli tire shortliand Asp, Glu etc tire subscripts represent tlie positions on tlie polypeptide chain. 

Glycine itself is almost neutral, and requires very little sodium hydroxide to give a pink colour with phenolphthalein some other amino-acids, e.g., glutamic acid, aspartic acid, etc., are definitely more acidic and consequently require more alkali for this purpose cf. footnote, p. 380). 

Another example is a chiral olefinic alcohol, which is disconnected at the double bond by a refro-Wittig transform. In the resulting 4-hydroxypentanal we recognize again glutamic acid, if methods are available to convert regio- and stereoselectively... 

Some ammo acids have side chains that bear acidic or basic groups As Table 27 3 indicates these ammo acids are characterized by three values The third pK reflects the nature of the side chain Acidic ammo acids (aspartic and glutamic acid) have acidic side chains basic ammo acids (lysine arginine and histidine) have basic side chains The isoelectric points of the ammo acids m Table 27 3 are midway between the pK values of the zwitterion and its conjugate acid Take two examples aspartic acid and lysine Aspartic acid has an acidic side chain and a pi of 2 77 Lysine has a basic side chain and a pi of 9 74... 

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)... 

Glutamic acid is formed m most organisms from ammonia and a ketoglutaric acid a Ketoglutaric acid is one of the intermediates m the tricarboxylic acid cycle (also called the Krebs cycle) and arises via metabolic breakdown of food sources carbohy drates fats and proteins... 

Ammonia reacts with the ketone carbonyl group to give an mine (C=NH) which is then reduced to the amine function of the a ammo acid Both mine formation and reduc tion are enzyme catalyzed The reduced form of nicotinamide adenine diphosphonu cleotide (NADPH) is a coenzyme and acts as a reducing agent The step m which the mine is reduced is the one m which the chirality center is introduced and gives only L glutamic acid... 

L Glutamic acid is not an essential ammo acid It need not be present m the diet because animals can biosynthesize it from sources of a ketoglutaric acid It is however a key intermediate m the biosynthesis of other ammo acids by a process known as transamination L Alanine for example is formed from pyruvic acid by transamination from L glutamic acid... 

In transamination an amine group is transferred from L glutamic acid to pyruvic acid An outline of the mechanism of transamination is presented m Figure 27 4... 

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... 

Nevertheless the biosynthesis of glutamine proceeds from glutamic acid The dif ference is that the endergonic process m Equation 1 is coupled with the strongly exer gome hydrolysis of ATP... 

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... 

---