Aspartic acid, deamination

Deamination. Aspartic acid and asparagine undergo a slow, reversible deamination reaction. The aspartic acid deamination reaction, which produces fumaric acid and ammonia, can be written as... 

Although the aspartic acid deamination reaction is slow and unimportant in present-day natural water systems, the reaction has geochemical implications, since it has been used to estimate the minimum NH4+ concentration in the oceans of the primitive earth (39). The argument is... 

E9.3 The deamination of aspartic acid is a reversible reaction catalyzed by the... 

Fischer s statement, cited above, that aspartic acid bears a simple relationship to the a-hydroxy acids and, consequently, to the sugars, was made with the explicit reservation that no Walden inversion may occur on deamination with nitrous acid (1896). This condition could not be retained. Furthermore, his conclusion that acetobromoglucose belongs to the /3-d series because it forms /3-D-glucosides is also inadmissible. It is amazing that these two cases seem to be the only ones in which he was misled by the then partially unknown, sometimes unfathomable phenomena of inversion. 

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

L-Asparaginase [a SPAR a gi nase] catalyzes the deamination of asparagine to aspartic acid and ammonia. The form of the enzyme used chemotherapeutically is derived from bacteria. 

Nitrogen incorporated into urea in the Ever originates from both intrahepatic and extrahep-atic sources. Urea contains two nitrogen atoms one is derived from ammonium, while the other is derived from aspartic acid. In Ever hepato-cytes, ammonium is generated by the oxidative deamination of glutamic acid, catalyzed by glutamate dehydrogenase,... 

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... 

Aspartase is ubiquitous in nature and has been studied in many bacterial species with the specific aim of using the enzyme to make L-aspartic acid [5,7-14], It catalyzes the reversible deamination of aspartic acid to fumaric acid (Scheme 2). This in vivo reaction precedes exclusively in the direction of fumarate, but in vitro it is readily reversible and can go to 100% completion. Much of the early characterization of aspartase was conducted on enzyme purified from strains of Escherichia coli B and W [15,16] and, for this reason, many of the early commercial processes were developed using the E. coU aspartase. 

The various decomposition reactions outlined in the preceeding section would remove amino acid from the buffered solutions, and if these reactions were significant compared with the k values, Equation 9 would have to be modified. Since the racemization was studied under anaerobic conditions, the decarboxylation and deamination reactions are the only important amino acid decomposition reactions. With the exception of the deamination of aspartic acid, the decomposition rates of the other amino acids studied were negligible compared with the racemization rate of the amino acid. Integration of Equation 9 yields... 

The rate of racemization of aspartic acid as a function of pH at 117.2°C is shown in Figure 1. The rates were calculated from Equation 12. The rates of deamination of aspartic acid at each pH value were calculated from the data given by Bada and Miller (38). The results in Figure 1 are the average values for samples heated for at least two... 

The same scaffold was used to design catalysts for pyridoxal phosphate-dependent deamination of aspartic acid to form oxaloacetate, one half of the transamination reaction [8], and oxaloacetate decarboxylation [14]. Catalysis was due to binding of pyridoxal phosphate in close proximity to His residues capable of rate limiting 1,3 proton transfer. A two-residue catalytic site containing one Arg and one Lys residue was found to be the most efficient decarboxylation agent, more efficient per residue than the Benner catalyst, most likely due to a combination of efficient imine formation, pK depression and transition state stabilization. 

It was found that the major mechanism in radiolysis of diaminobutyric acid in oxygenated solution is oxidative deamination on < - or y-position. This is clear from a comparison of the decrease in the content of diaminobutyric acid (G/-M/2.65), with the yield of ammonia (G 2.1) and with the yields of deaminated products (S G 2.0). Aside from carbonyl substances and ketoamino acids, /2-alanine and aspartic acid have been found among the products of oxidative deamination. In oxygen-free atmosphere, two of the main radiation mechanisms are reductive deamination (G/-M/1.4 and G NH3 1.2) and recombination reactions leading to products of higher molecular weight. 

Bada, J.L. and Miller, S.L., 1968b. Equilibrium constant for the reversible deamination of aspartic acid. Biochemistry, 7 3403—3408. 

As mentioned in Section 1.1, the first diazotization of amines, followed by dediazoniation, was carried out by Piria in 1848, well before Griess discovered and isolated aromatic diazo compounds (1858). Piria added an impure HNO3 —HCl solution to a mixture of asparagine and aspartic acid in water and obtained malic acid (7-1). It was not possible for Piria, however, to realize that the primary reaction products were diazonium ions. Yet, Piria s process was one of the few types of reaction via aliphatic diazonium ions that became important for synthetic purposes, after Ingold s group (Brewster et al., 1950) discovered that a-amino acids undergo clean retentive deamination (see Sect. 7.7). 

The cost of L-malic acid can be dramatically reduced by preparing it from L-aspartic acid, the current price of which is only 53.70 for 2 Kg. This process requires only a single step, in which the amino group of aspartic acid is converted to the desired hydroxyl function under nitrous acid deamination conditions [2]. The configuration of the chiral center is retained, affording 1 with 97% ee. 

Nitrous acid deamination of D-aspartic acid (884) proceeds with retention of configuration to afford D-malic acid (885) directly and in high yield with 97% ee [2]. The cost of D-aspartic acid is approximately one-fifth that of D-malic acid. 

A racemase brings about inversion of the relatively cheap (L)-isomers of alanine or aspartic acid, but not of (D)-phenylalanine. Only (L)-phenylalanine is deaminated by an (L)-amino acid deaminase, whereas (D)-phenylalanme is not. The latter is generated by ammonia transfer from (D)-alanine or (D)-aspar-tic acid with a (D)-amino acid aminotransferase. The equilibria are moved in favour of the product, either by the metabolism of pyruvic acid or oxosuccinic acid. Since (L)-amino acid deaminases, like (D)-amino add aminotransferases, are non-specific, they also permit the preparation of a variety of other (D)-amino acids. [58]... 

Unlike the D-amino acid oxidase of Krebs, the D-aspartic oxidase is not inhibited by benzoate. Once the n-aspartate is deaminated, the residual carbon moiety is completely oxidized by the homogenate preparations. 

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. 

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