N-Glutamate

Poly-y-benzyl -n-glutamate -635 Ethylene dichloride 0 Hydrazine... 

This shows that three more constraints are needed. If we view the three reactions as the points of a triangle, we can view the three constraints as the sides of the triangle. There are a number of ways to do this, but the three constraints used here are coni n(atp) + n(asparagineL) con2 n(atp) -t- n(glutamate) con3 n(aspartate) + n(ppi)... 

Fig. 8. Moffitt plots at two different values of Xo, 212 and 216 m, for the dispersions of a copolymer of 6% i.-tyrosine with n-glutamic acid (PTGA) from 700 m i down to 240 m/i.. The plots based upon 212 m/i are an extension of the visible and near ultraviolet data represented in detail in Fig. 7. Helical form in 0.1 M phosphate buffer,...

In addition to n-alanine and n-glutamate, many bacterial cell walls also contain meso-diaminopimelate (DAP) [2]. DAP is produced by epimerization from l,l-DAP to d,l-DAP by the cofactor independent diaminopimelate epimerase [97, 98]. The structure of this enzyme has been solved and two cysteines in the active site were proposed to be the acid-base catalysts [99]. The pattern of label incorporation from tritiated water is consistent with a two-base mechanism [97]. The enzyme has been shown to be stoichiometrically inhibited by the thiol alkylating agent aziDAP [97]. Interestingly, DAP epimerase has an equilibrium constant of 2 (Keq = [d,l]/[l,l]) duc to the statistically expected higher concentration of the [d,l] form at equilibrium between these species [100]. 

Changes in percent of and amounts of in amino acids in tea leaves during aerobic or anaerobic incubation after feeding N-glutamic acid for 6 hours... 

Although D-amino acids do not generally occur in proteins, they do serve some special functions in the structure of bacterial cell walls and peptide antibiotics. Bacterial peptidoglycans (see Fig. 20-23) contain both D-alanine and n-glutamate. D-Amino acids arise directly from the l isomers by the action of amino acid racemases, which have pyridoxal phosphate as cofactor (see Fig. 18-6). Amino acid racemization is uniquely important to bacterial metabolism, and enzymes such as... 

Commercial preparations of pig heart glutamate-oxaloacetate transaminase have been screened for their ability to transaminate various a-keto acids with l-[ N]glutamate (32). In addition to l-[ N]aspartate, enzyme preparations were able to catalyze the formation of labeled tyrosine, phenylalanine, leucine, and dihydroxyphenylalanine, as demonstrated by HPLC (17). However, these amino acids have not yet been obtained in radiopure form by this method. The -keto acid analogs of valine and tryptophan were not transaminated by the enzyme preparations. Glutamate-oxaloacetate transaminases obtained from several commercial sources have varying abilities to transaminate the -keto acid... 

Label concentrations in the heart and submaxillary salivary glands were similar to those for l-[ N]glutamate (35). 

Fig. 1 A, PTC-amino acid standard (200 pmol), including phosphoserine (PH-S), aspartate (N), glutamate (D), phosphothreonine (PH-T), hydroxyproline (OH-P), galactosamine (Gal), serine (S), glycine (G), histidine (H), arginine (R), threonine (T), alanine (A), proline (P), tyrosine (Y), valine (V), methionine (M), cysteine (C), isoleucine (I), leucine (L), norleucine (NLE, 1 nmol internal standard), phenylalanine (F), excess reagent (Re), and lysine (K). B, Analysis of a human fingerprint, taken up from a watch glass using a mixture of water and ethanol.

More specific labelling may be obtained in a biosynthetic process using enzymic methods of synthesis. The preparation of amino acids by the reductive amination of 2-keto acids is well known. Indeed, the synthesis of N-labelled amino acids by this route is among the earliest literature on the preparation of compounds labelled with stable isotopes [73], Such reductions can be carried out enzymically and L - [a- N] glutamic acid has been prepared in good yield from 2-oxoglutaric acid and N-labelled ammonium chloride in the presence of reduced nicotinamide adenine dinucleotide phosphate [74],... 

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