Decarboxylases aspartate decarboxylase

Aspartate undergoes /3-decarboxylation to /S-alanine unlike most amino acid decarboxylases, aspartate decarboxylase is not pyridoxal phosphate-dependent, but has a catalytic pyruvate residue, derived by postsynthetic modification of a serine residue (Section 9.8.1). Pantothenic acid results from the formation of a peptide bond between /3-alanine and pantoic acid. 

ASPARTYLCLUCOSAMINIDASE ASPARTATE AMINOTRANSFERASE ASPARTATE AMMONIA-LYASE ASPARTATE CARBAMOYLTRANSFERASE ASPARTATE a-DECARBOXYLASE ASPARTATE /3-DECARBOXYLASE ASPARTATE KINASE d-ASPARTATE OXIDASE ASPARTATE RACEMASE... 

D-aspartic acid DL-aspartic acid L-aspartate decarboxylase... 

Also Tanabe have extended the use of that aspartic acid producing process by using the L-aspartic acid as the substrate for L-alanine production using P. dacunae cells with L-aspartate decarboxylase activity. This process has been operating since 1982 using sequential colunms of iimnobihsed E. coli and P. dacunae cells (Chibata, Tosa and Takamatsu, 1987). Also, DL-aspartic acid can be used as the feed in this process. Then, D-aspartic acid is obtained as an additional product, for which there is a modest demand. 

Aspartate aminotransferase 284, 285 j6-Aspartate decarboxylase 81, 285 Aspartate transcarbamoylase 298, 360 Aspartyl proteases—see carboxyl proteases Aspirin 66, 67 Association rate constants collision theory 54, 158,159 electrostatic enhancement 159-161... 

The intermediate 9.14 is probably generated during the suicide inhibition of /3-aspartate decarboxylase,21 aspartate aminotransferase,22 and alanine racemase23,24 by /3-chloroalanine. These enzymes are inactivated by the intermediate, since they have not evolved to cope with it during the normal course of reaction. 

Tanabe produces L-alanine from L-aspartate (see above) by decarboxylation with the help of i-aspartate-//-decarboxylase (E.C. 4.1.1.12) from Pseudomonas dacunhae (Figure 7.18). 

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. 

A similar process is also used for the production of L-malic acid from fumarate, in this case using a hydratase enzyme derived from Brevibacterium ammoniagenes. Another variation of the Tanabe technology involves the synthesis of L-alanine from L-aspartic acid through the use of immobilized whole cells (P dacunae) containing aspartate-decarboxylase. 

Scheme XVIII. PLP-substrate Schiff s base geometry for a single-base mechanism (A) and possible geometry for a two-base mechanism (B) for aspartate-/ -decarboxylase.

Other pyruvate-containing enzymes include aspartate -decarboxylase from Escherichia coli, the enzyme that catalyzes the formation of -alanine for the synthesis of pantothenic acid (Section 12.2.4) proline reductase from Clostridium sticklandiv, phosphatidylserine decarboxylase from E. coli and phenylalanine aminotransferase from Pseudomonas fluorescens. Phospho-pantetheinoyl cysteine decarboxylase, involved in the synthesis of coenzyme A (Section 12.2.1), and S-adenosylmethionine decarboxylase seem to be the only mammalian pyruvoyl enzymes (Snell, 1990). 

Figure 12.3. Biosynthesis ofpantothenic acid. Oxo-pantoate hydroxymethyltransferase, EC 2.1.2.11 dehydropantoate reductase, EC 1.1.1.169 and aspartate -decarboxylase, EC 4.1.1.12.

It is noteworthy that the biocatalytic formation of a methyl group via decarboxylation can also be realized on technical scale. A decarboxylation of L-aspar-agine in the presence of an aspartate //-decarboxylase allows an efficent synthesis of L-alanine [86]. 

Lin C-T, Li J-Z, Wu J-Y (1983) Immunocytochemical localization of L-glutamate decarboxylase, gamma-aminobutyric acid transaminase, cysteine sulfinic acid decarboxylase, aspartate aminotransferase and somatostatin in rat retina. Brain Res 270 273-283. 

The biocatalytic synthesis can be extended towards the production of L-alanine when using additionally an L-aspartate decarboxylase for a subsequent decarboxylation step. Such a process has been reported by Tanabe Seiyaku, and gave the desired L-alanine in 86% yield and with 99% ee [37]. A key feature of the decarboxylase process is the high substrate concentration of 2.5 M, and a space-time yield of 170 g/(L d) of L-alanine. Based on this two-step approach, L-alanine has been produced in annual amounts of ca. 60 tons [32b, 37]. 

L-Alanine is produced from L-aspartate by a one-step enzymatic method using aspartate -decarboxylase ... 

Pyruvoyl cofactor is derived from the posttranslational modification of an internal amino acid residue, and it does not equilibrate with exogenous pyruvate. Enzymes that possess this cofactor play an important role in the metabolism of biologically important amines from bacterial and eukaryotic sources. These enzymes include aspartate decarboxylase, arginine decarboxylase," phosphatidylserine decarboxylase, . S-adenosylmethionine decarboxylase, histidine decarboxylase, glycine reductase, and proline reductase. ... 

The enzyme aspartate decarboxylase (EC 4.1.1.11) will decarboxylate aminomalonic acid in H20 to yield (25)-[2- HJglycine and will also transaminate glyoxylic acid in H20 to yield (2K)-[2- H]]glycine (78). The chirality of the product was assayed using the pro-S specific D-amino acid oxidase (EC 1.4.3.3). 

Figure 2 The stability of the Ijnmoblllzed organism containing aspartate- -decarboxylase was assessed by contlnoous infusion of 1.5M aspartate (pH 8.5), 0.1 mM pyrldozal-5-lHiosphate, 0.5 mM sodium pyruvate at 37°C through a 750 ml volume continuous stirred reactor containing 75 mL of catalyst (0.2g Pseudomonas daeunhae/ml beads) with the rate adjusted to provide 99% conversion.

Also known as beta-alanine because of its similarity to the canonical amino acid L-lysine, it has been overproduced in E. coli. A strain was prepared, which included an aspartate decarboxylase gene panD) from C. glutamicum, overexpression of aspartase (aspA) and phosphoenolpyruvate carboxylase (ppc), and acetyl-CoA synthase (acs) and it resulted in total titers of 32 g 1 after 39 h from rich media supplemented by glucose and ammonium sulfate [61]. 

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