Amino acids L-aspartate

There are numerous further appHcations for which maleic anhydride serves as a raw material. These appHcations prove the versatiHty of this molecule. The popular artificial sweetener aspartame [22839-47-0] is a dipeptide with one amino acid (l-aspartic acid [56-84-8]) which is produced from maleic anhydride as the starting material. Processes have been reported for production of poly(aspartic acid) [26063-13-8] (184—186) with appHcations for this biodegradable polymer aimed at detergent builders, water treatment, and poly(acryHc acid) [9003-01-4] replacement (184,187,188) (see Detergency). 

Oxaloacetate + a-amino acid--> L-aspartate + a-keto acid... 

Aspartame is the generic name for IV-ai-aspartyl-L-phenylalanine methyl ester. It is composed of two amino acids, L-aspartic acid and L-phenylalanine, joined by a methyl ester link. It was discovered in 1965 by J. Schlatter at the G.D. Searle Laboratories. It is a white crystalline product and its solubility in water is 10 g/1 at 20°C this figure increases at elevated temperatures and in acidic conditions (Ajinomoto Aspartame Technical Bulletin, 2003). It is sparingly soluble in other solvents. 

Lyases are an attractive group of enzymes from a commercial perspective, as demonstrated by then-use in many industrial processes.240 They catalyze the cleavage of C-C, C-N, C-O, and other bonds by means other than hydrolysis, often forming double bonds. For example, two well-studied ammonia lyases, aspartate ammonia lyase (aspartase) (E.C. 4.3.1.1) and phenylalanine ammonia lyase (PAL) (E.C. 4.3.1.5), catalyze the trans-elimination of ammonia from the amino acids, l-aspartate and L-phenylalanine, respectively. Most commonly used in the synthetic mode, the reverse reaction has been used to prepare the L-amino acids at the ton scale (Schemes 19.30 and 19.31).240 242 These reactions are conducted at very high substrate concentrations such that the equilibrium is shifted, resulting in very high conversion to the amino acid products. 

Another example, also reported by Ugi and co-workers, is the combination of an Ugi five center 4-component reaction (U-5C-4CR) with a Passerini-3CR (Scheme 16) [102]. This one-pot procedure uses an a-amino acid (L-aspartic acid, 168) as a 2-center-1-component input, which explains the origin of the U-5C-4CR. 

Alitame [L-a-aspartyl-N-(2,2,4,4-tetramethyl-3-thietanyl)-D-alaninamide] is a sweetener based on an amino acid. It is a very intense sweetener, possessing a sweetening power of about 2000 times that of sucrose. It also exhibits a clean sweet taste similar to sucrose. Although it is metabolized, so little is needed that its caloric contribution is insignificant. Alitame is prepared from the amino acids, L-aspartic acid, D-alamine, and a novel amine [9]. 

The fact that impurities can be incorporated by growth on a particular face is exploited in doping of organic materials for electronic use. For example, triglycine sulfate crystals are doped throughout the lattice with alanine by growth only on the 010 face held in a crystal holder (White et al. 1976). A number of amino acids (L-aspartic, L-valine, L-leucine and L-phenylalanine) have been observed to be incorporated into the lattice of glutamic acid... 

Alitame [II] is nutritive, but due to its intense sweetness, the amounts used are small enough for it to be considered and classified as a nonnutritive sweetener. Alitame is formed from the amino acids L-aspartic acid and o-alanine with a novel amide moiety (formed from 2,2,4,4-tetra-methylthienanylamine). Alitame exhibits superior stability under a variety of conditions because of its unique amide group. Alitame has been approved... 

L-threonine belongs to the aspartic family of amino acids. L-aspartate is synthesized from oxaloacetate, an intermediate of TCA cycle, by aspartate transaminase (Table 14.1) that is encoded by the aspC gene in E. coli (Fotheringham et al. 1986) and by aspA in C. glutamicum (Marienhagen et al. 2(X)5). On substrates of carbohydrates,... 

Aspartame was discovered by accident by Jim Schlatter, a chemist at G.D. Searle in 1965. Jim Schlatter was working on drugs for the treatment of gastric ulcers when he spilled some aspartyl-phenylalanine on his hand. He later licked his finger and noticed the sweet taste of the compound, which later became aspartame. Aspartame is the methyl ester of the dipeptide of the natural amino acids L-aspartic acid and L-phenylalanine. There are four possible diastereoiso-mers for aspartame but aspartame is the only one having sweetening properties. The taste of aspartame would not have been predictable based on its amino acid constituents. 

Enzymatic Process. Chemically synthesized substrates can be converted to the corresponding amino acids by the catalytic action of an enzyme or the microbial cells as an enzyme source, t - Alanine production from L-aspartic acid, L-aspartic acid production from fumaric acid, L-cysteine production from DL-2-aminothiazoline-4-catboxyhc acid, D-phenylglycine (and D-/> -hydtoxyphenylglycine) production from DL-phenyUiydantoin (and DL-/)-hydroxyphenylhydantoin), and L-tryptophan production from indole and DL-serine have been in operation as commercial processes. Some of the other processes shown in Table 10 are at a technical level high enough to be useful for commercial production (24). Representative chemical reactions used ia the enzymatic process are shown ia Figure 6. 

It is a peptide containing 27 amino acid residues containing the amino acids L-histidine (His) L-aspartic acid (Asp) L-serine (Ser) glycine (Gly) L-threonine (Thr) L-phenyl-alanine (Phe) L-glutamic acid (Glu) L-glutamine [Glu(NHj)] L-leucine (Leu) L-arginine (Arg) L-alanine (Ala) and L-valinamide (Va -NHj). 

The elimination of the amino donor, L-aspartic acid, resulted in an almost complete reduction of activity. Neither cell permeabilisation nor cofactor (pyridoxalphosphate) addition were essential for L-phenylalanine production. Maximum conversion yield occurred (100%, 22 g r) when the amino donor concentration was increased. Aspartic add was a superior amino donor to glutamic add 35 g l 1 was used. 

A possible explanation for the superiority of the amino donor, L-aspartic add, has come from studies carried out on mutants of E. coli, in which only one of the three transaminases that are found in E. coli are present. It is believed that a branched chain transaminase, an aromatic amino add transaminase and an aspartate phenylalanine aspartase can be present in E. coli. The reaction of each of these mutants with different amino donors gave results which indicated that branched chain transminase and aromatic amino add transminase containing mutants were not able to proceed to high levels of conversion of phenylpyruvic add to L-phenylalanine. However, aspartate phenylalanine transaminase containing mutants were able to yield 98% conversion on 100 mmol l 1 phenylpyruvic acid. The explanation for this is probably that both branched chain transaminase and aromatic amino acid transminase are feedback inhibited by L-phenylalanine, whereas aspartate phenylalanine transaminase is not inhibited by L-phenylalanine. In addition, since oxaloacetate, which is produced when aspartic add is used as the amino donor, is readily converted to pyruvic add, no feedback inhibition involving oxaloacetate occurs. The reason for low conversion yield of some E. coli strains might be that these E. cdi strains are defident in the aspartate phenylalanine transaminase. 

L-Asparaginase, an enzyme derived from E. coli or Erwinia carotovora, has been employed in cancer chemotherapy where its selectivity depends upon the essential requirement of some tumours for the amino acid L-asparagine. Normal tissues do not require this amino acid and thus the enzyme is administered with the intention of depleting tumour cells of asparagine by converting it to aspartic acid and ammonia. Whilst L-asparaginase showed promise in a variety of experimentally induced tumours, it is only useful in humans for the treatment of acute lymphoblastic leukaemia, although it is sometimes used for myeloid leukaemia. 

The amino acid L-glutamate is the main excitatory neurotransmitter of the central nervous system (Fonnum, 1984). Glutamate exerts its excitatory effects either by activation of several G-protein-coupled metabotropic glutamate receptors or by induction of ion fluxes by different classes of ionotropic receptors. The NMDA receptor is one of those glutamate-gated ion channels which got its name from its selective artificial agonist NMDA (N-methyl-D-aspartate) and which controls slow but persistent ion fluxes of Na+, K+, and Ca2+ across the cell membrane. 

Separation of three amino acids (l-valine, L-alanine, and L-aspartic acid, 300 pM) have been detected using 0.5 mM Ru(bpy)2+ in the run buffer. The ECL emission intensity can be enhanced by increasing the voltage across the electrodes. However, with the floating electrodes, such an increase could only be achieved by increasing the separation voltage [725],... 

The details of the pathway for de novo biosynthesis are shown in Fig. 15-16. The amino acid L-glutamine is the substrate providing nitrogen atoms for reactions 1, 4 and 14, catalyzed by amido phosphoribosyltransferase, FGAM synthetase and GMP synthetase, respectively. Glycine is a substrate at reaction 2, and L-aspartate at reactions 7 and 11. P-Rib-PP is a substrate and activator for amidophosphoribosyltransferase, which is subject to inhibition by AMP. IMP and GMP and by polyglutamate derivatives of dihydrofolate. 

It is also possible to convert nonchiral readily available industrial organic chemicals into valuable chiral natural-analogue products. This is demonstrated by the conversion of achiral fumaric acid to L(-)-malic acid with fumarase as the active enzyme. The same compound is converted to the amino acid L(-h)-aspartic acid by Escherichia bacteria that contain the enzyme aspartase. If pseudomonas bacteria are added, another amino acid L-alanine is formed (Eq. 9.10). 

Asparaginase is an enzyme that acts by breaking down the amino acid L-asparagine to aspartic acid and ammonia. It interferes with the growth of malignant cells that cannot synthesize L-asparagine. Its action is reportedly specific for the Gi phase of the cell cycle. It is used mainly for the induction of remissions in acute lymphoblastic leukemia. 

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