Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Aspartase 25.35 - -Aspartate

Thus, for aspartase (aspartate ammonia-lyase) the reaction direction is L-aspartate - fumarate + NH 3. The enzyme uses L-aspartate but not the D-enantiomer the product is fumarate not maleate. Hence, this enzyme has strict substrate and product selectivity. For greater detail, this could read strict substrate enantioselectivity and product diastereoselectivity. If necessary, information concerning prochirality could be conveyed in the same way for this same enzyme there is substrate diastereoselectivity for the protons at C-3. [Pg.76]

Figure 17-12. Enzymatic production of D-alanine by combination of aspartase, aspartate racemase, and D-amino acid aminotransferase reactions. Figure 17-12. Enzymatic production of D-alanine by combination of aspartase, aspartate racemase, and D-amino acid aminotransferase reactions.
The transport of ammonia appears to occur through cell wall ammonia membrane channels called ammonia transporters (Amt proteins). Ammonia, having been transported, is, at least in principle, capable of being utilized by, for example, the enzyme aspartase (aspartate ammonia-lyase, EC 4.3.1.1) that catalyzes the reversible deamination of aspartate (Asp, D) to fumarate (Equation 12.2). [Pg.1132]

These molecules are derived from aspartic acid, itself formed from members of the Krebs cycle. In plants and micro-organisms fumaric acid is combined with ammonia in the presence of aspartase, whilst in mammals which do not possess aspartase, aspartic acid is formed by reductive deamination of oxaloacetate in a reaction of imknown mechanism. [Pg.245]

Similarly, Bacterium cadaveris includes the enzyme L-aspartase (aspartate ammonia lyase). This microorganism can be fixed to a PNH3 electrode and the enzyme catalyses the following reaction for the determination of aspartate [238] ... [Pg.150]

L-aspartic acid fumaric acid + NH aspartase E. coii ... [Pg.292]

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. [Pg.268]

Of industrial importance at present is die biotransformation of fumarate to L-aspartic add by Escherichia cdi aspartase. Modified versions have been developed, such as the continuous production of L-aspartic add using duolite-ADS-aspartase. A conversion higher than 99% during 3 months on a production scale has been achieved. [Pg.286]

L-aspartic add has been produced on an industrial scale by the Tanabe Seiyaku Co Ltd, Japan, in a batch wise process using whole cells of Escherichia coli with high aspartase activity. In this process, L-aspartic add is produced from fumaric add and ammonia using aspartase, as described in Figure A8.13. [Pg.287]

Many enzymes have absolute specificity for a substrate and will not attack the molecules with common structural features. The enzyme aspartase, found in many plants and bacteria, is such an enzyme [57], It catalyzes the formation of L-aspartate by reversible addition of ammonia to the double bond of fumaric acid. Aspartase, however, does not take part in the addition of ammonia to any other unsaturated acid requiring specific optical and geometrical characteristics. At the other end of the spectrum are enzymes which do not have specificity for a given substrate and act on many molecules with similar structural characteristics. A good example is the enzyme chymotrypsin, which catalyzes hydrolysis of many different peptides or polypeptides as well as amides and esters. [Pg.221]

This enzyme [EC 4.3.1.1], also known as aspartase and fumaric aminase, catalyzes the conversion of aspartate to fumarate and ammonia. [Pg.68]

Figure 25. Trace enantiomer analysis of L-aspartic acid (obtained by enzymatic amination of fumarate with L-aspartase and determined as the A -trifluoroacetyl-O-methyl ester) on i.-Chirasil-Val31 [20 mx0.25 mm (i.d.) glass capillary column, 90 CC, 0.4 bar hydrogen] with detection by GLC MS selected ion monitoring (mj 198.1) and multiscanning chromatography (MSC, 8 scans)186. Figure 25. Trace enantiomer analysis of L-aspartic acid (obtained by enzymatic amination of fumarate with L-aspartase and determined as the A -trifluoroacetyl-O-methyl ester) on i.-Chirasil-Val31 [20 mx0.25 mm (i.d.) glass capillary column, 90 CC, 0.4 bar hydrogen] with detection by GLC MS selected ion monitoring (mj 198.1) and multiscanning chromatography (MSC, 8 scans)186.
L-aspartic acid by ammonia addition to fumaric acid by aspartase (from E. coli)... [Pg.416]

Other enzymes that catalyze elimination reactions that produce fumarate are aspartate ammonia-lyase (aspartase),63 argininosuccinate lyase (Fig. 24-10, reaction g),64/65 and adenylosuccinate lyase... [Pg.685]

Fig. 25-15). In every case it is NH3 or an amine, rather than an OH group, that is eliminated. However, the mechanisms probably resemble that of fumarate hydratase. Sequence analysis indicated that all of these enzymes belong to a single fumarase-aspartase family.64 65 The three-dimensional structure of aspartate ammonia-lyase resembles that of fumarate hydratase, but the catalytic site lacks the essential HI 88 of fumarate hydratase. However, the pKa values deduced from the pH dependence of Vmax are similar to those for fumarase.64 3-Methylaspartate lyase catalyzes the same kind of reaction to produce ammonia plus czs-mesaconate.63 Its sequence is not related to that of fumarase and it may contain a dehydroalanine residue (Chapter 14).66... [Pg.685]

Ash, amount from tissue 31 Asparagine (Asn, N) 53s Aspartase 526 Aspartate 737s... [Pg.907]

Owing to the commercialization of Aspartame the demand for i-aspartic acid increased steeply. i-Aspartate can be produced by enantioselective addition of ammonia to fumaric acid catalyzed by aspartase (E.C. 4.3.1.1) (Figure 7.17). [Pg.180]

Naidja, A., and Huang, P. M. (1996). Deamination of aspartic acid by aspartase-Ca-montmorillonite complex. J. Mol. Catal. A Chem. 106, 255-265. [Pg.140]

Historically, L-aspartic acid was produced by hydrolysis of asparagine, by isolation from protein hydrolysates, or by the resolution of chemically synthesized d,L-aspartate. With the discovery of aspartase (L-aspartate ammonia lyase, EC 4.3.1.1),57 fermentation routes to L-aspartic acid quickly superseded the initial chemical methods. These processes are far more cost effective than the fermentation routes, and aspartate is now made exclusively by enzymatic methods that use variations of the general approach outlined in Scheme 2.19.53-57-65... [Pg.24]

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. [Pg.379]

Aspartase exhibits incredibly strict substrate specificity and thus is of little use in the preparation of L-aspartic acid analogues. However, a number of L-phenylalanine analogues have been prepared with various PAL enzymes from the yeast strains Rhodotorula graminis, Rhodotorula rubra, Rhodoturula glutinis, and several other sources that have been cloned into E. call.243 241 Future work in this area will likely include protein engineering to design new enzymes that offer a broader substrate specificity such that additional L-phenylalanine analogues could be prepared. [Pg.380]

Alanine and aspartic acid are produced commercially utilizing enzymes. In the case of alanine, the process of decarboxylation of aspartic acid by the aspartate decarboxylase from Pseudomonas dacunhae is commercialized. The annual world production of alanine is about 200 tons. Aspartic acid is produced commercially by condensing fumarate and ammonia using aspartase from Escherichia coli. This process has been made more convenient with an enzyme immobilization technique. Aspartic acid is used primarily as a raw material with phenylalanine to produce aspartame, a noncaloric sweetener. Production and sales of aspartame have increased rapidly since its introduction in 1981. Tyrosine, valine, leucine, isoleucine, serine, threonine, arginine, glutamine, proline, histidine, cit-rulline, L-dopa, homoserine, ornithine, cysteine, tryptophan, and phenylalanine also can be produced by enzymatic methods. [Pg.1360]

Aspartase. Tanabe Seiyaku has used aspartase in lysed E. coli cells immobilized by entrapment in polyacrylamide (3) or K-carra-geenan (38) for production of aspartic acid since 1973. Using a substrate stream containing 1 M ammonium fumarate and 1 mM Mg2+ at pH 8.5 and 37°C, a continuous, automated bioreactor with a 120-day half-life will produce L-aspartate at 60% of the cost of a batch fermentation (3). Recently, a process for immobilization of the cells in polyurethane has also been described (37). [Pg.249]

Examples of the use of immobilized enzymes in food processing and analysis have been listed by Olson and Richardson (1974) and Hultin (1983). L-aspartic acid and L-malic acid are produced by using enzymes contained in whole microorganisms that are immobilized in a polyacrylamide gel. The enzyme aspartase from Escherichia coli is used for the production of aspartic acid. Fumarase from Brevibacterium ammoni-agenes is used for L-malic acid production. [Pg.319]

Thus, in the action of the enzyme aspartase, fumaric acid, 39, is transformed into L-aspartic acid, 40. This process can be considered as a result of three steps ... [Pg.68]

Such interference falls into two classes competitive substrates and substances that either aaivate or inhibit the enzyme. With some enzymes, such as urease, the only substrate that reacts at reasonable rate is urease hence, the urease-coated electrode is specific for use (59, 165). Likewise, uricase acts almost specifically on uric acid (167), and aspartase on aspartic acid (8, 168). Others, such as penicillinase and amino oxidase, are less specific (63,169,170). Alcohol oxidase responds to methanol, ethanol, and allyl alcohol (171, 172). Hence, in using electrodes of these enzymes, the analyte must be separated if two or more are present (172). Assaying L-amino acids by using either the decarboxylative or the deaminating enzymes, each of which acts specifically on a different amino... [Pg.88]

The industrial preparation of L-aspartic acid by the amination of ( )-2-butenedioic acid (fumaric acid) made use of some form of immobilized aspartase (free cell), which were replaced by microbial whole cells, resulting in reduced costs and simplified operations 38a d. [Pg.747]


See other pages where Aspartase 25.35 - -Aspartate is mentioned: [Pg.867]    [Pg.79]    [Pg.403]    [Pg.17]    [Pg.312]    [Pg.287]    [Pg.93]    [Pg.107]    [Pg.1378]    [Pg.2]    [Pg.13]    [Pg.180]    [Pg.180]    [Pg.52]    [Pg.209]    [Pg.110]    [Pg.91]    [Pg.1409]    [Pg.255]    [Pg.747]    [Pg.747]   
See also in sourсe #XX -- [ Pg.407 ]




SEARCH



Aspartase

© 2024 chempedia.info