D-Glutamate

D-glutamic acid L-glutamic acid Glu decarboxylase + Glu racemase iMctohac. brevis 207... 

The existence of protein receptors in the tongues of mice and cows have been shown. Monosodium L-glutamate MSG [142-47-2] is utilized as a food flavor enhancer in various seasonings and processed foods. D-Glutamate is tasteless. L-Aspartic acid salt has a weaker taste of umami. Glycine and L-alanine are slightly sweet. The relationship between taste and amino acid stmcture has been discussed (222). 

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. 

Protein Arginine d Glutamic Acid d e Histidine b d e Lysine b d Ornithine d TJrrosine ... 

Mohadger, Y., and Wilkes, G. L., The effect of casting solvent on the material properties of polyCY-methyl-D-glutamate), J. Polym. Sci. Polvm. Phys. Ed., 14. 963-980, 1976. 

Fig. 8.1 Biosynthesis of peptidoglycan. The large circles represent A -acetylglucosamine orN-acetylmuramic acid to the latter is linked initially a pentapeptide chain comprising L-alanine, D-glutamic acid and meso-diaminopiraelic acid (small circles) terminating in two D-alanine residues (small, darker circles). The lipid molecule is undecaprenyl phosphate. In the initial (cytoplasm) stage where inhibition by the antibiotic D-cycloserine is shown, two molecules of Dalanine (small circles) are converted by an isomerase to the D-forms (small, darker circles), alter which a ligase joins the two D-alanines together to produce a D-alanyl-D-alanine dipeptide.

Figure 10 Capillary ion analysis of 30 anions 1 = thiosulfate, 2 = bromide, 3 = chloride, 4 = sulfate, 5 = nitrite, 6 = nitrate, 7 = molybdate, 8 = azide, 9 = tungstate, 10 = monofluorophosphate, 11 = chlorate, 12 = citrate, 13 = fluoride, 14 = formate, 15 = phosphate, 16 = phosphite, 17 = chlorite, 18 = galactarate, 19 = carbonate, 20 = acetate, 21 = ethanesulphonate, 22 = propionate, 23 = propanesulphonate, 24 = butyrate, 25 = butanesulphonate, 26 = valerate, 27 = benzoate, 28 = D-glutamate, 29 = pentane-sulphonate and 30 = D-gluconate. Experimental conditions fused silica capillary, 60 cm (Ld 52 cm) x 50 p i.d., voltage 30 kV, indirect UV detection at 254 nm, 5 mM chromate, 0.5 mM NICE-Pak OFM Anion-BT, adjusted to pH 8.0, with 100 mM NaOH. (From Jones, W. R. and Jandik, R, /. Chromatogr., 546, 445,1991. With permission.)...

Figure 14 Chiral separation of dansyl amino acids by chiral polyacrylamide gel electrophoresis. Peak identification 1 = dansyl-L-glutamic acid, 2 = dansyl-D-glutamic acid, 3 = dansyl-L-serine, 4 = dansyl-D-serine, 5 = dansyl-L-leucine, 6 = dansyl-D-leu-cine. (From Guttman, A., Paulus, A., Cohen, A. S., Grinberg, N. and Karger, B. L., /. Chromatogr., 448, 41, 1988. With permission.)...

FIGURE 3.8 Kainate and AMPA activate different current responses in the different classes of kainate and AMPA receptors (a) the AMPA receptor, GluRl (b) and (c) kainate receptors (d) glutamate + glycine activation of the NMDA receptor. The current response is characterized by a slow onset and offset compared to the kainate and AMPA receptors. 

Rundlett, K.L., Armstrong, D.W. (1994). Evaluation of free D-glutamate in processed foods. Chirality 6, 227-282. 

King EC, Watkins WJ, Blacker AJ et al (1998) Covalent modification in aqueous solution of poly-y-D-glutamic acid from Bacillus licheniformis. J Polvin Sci A Polym Chem 36 1995-1999... 

Prodhomme EJF, Tutt AL, Glennie MJ et al (2003) Multivalent conjugates of poly-y-D-glutamic acid from Bacillus licheniformis with antibody F(ab ) and glycopeptide ligands. Bioconjug Chem 14 1148-1155... 

Schneerson R, Kubler-Kielb J, Liu TY et al (2003) Poly(y-D-glutamic acid) protein conjugates induce IgG antibodies in mice to the capsule of Bacillus anthracis a potential addition to the anthrax vaccine. Proc Natl Acad Sci USA 100 8945-8950... 

Wang TT, Fellows PF, Leighton TJ et al (2004) Induction of opsonic antibodies to the gamma-D-glutamic acid capsule of Bacillus anthracis by immunization with a synthetic peptide-carrier protein conjugate. FEMS Immunol Med Microbiol 40 231-237... 

Joyce J, Cook J, Chabot D et al (2006) Immunogenicity and protective efficacy of Bacillus anthracis poly-y-D-glutamic acid capsule covalently coupled to a protein carrier using a novel triazine-based conjugation strategy. J Biol Chem 281 4831 -843... 

Kubler-Kielb J, Liu TY, Mocca C et al (2006) Additional conjugation methods and immunogenicity of Bacillus anthracis poly-y-D-glutamic acid-protein conjugates. Infect Immun 74 4744 1749... 

Scheme 2 Antibiotics related to penicillin. Note that in sulfazecin, 8, the dipeptide unit contains D-glutamate and D-alanine...

A further modification is a single (3-lactam ring as found in the mon-obactams. Characteristically, there is a sulfonate residue (derived from sulfate) on the nitrogen atom. An example is sulfazecin 8 from Pseudomonas acidophila and P. mesoacidophila. This material also contains a dipeptide unit of D-glutamate and D-alanine (Scheme 2). Pharmaceutical chemists have synthesized many variations on the (3-lactam structure and have devised semisynthetic processes. The resulting materials are not natural products and are beyond the scope of this article. 

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