Dehydrogenase phenylalanine

Two reactions for the production of L-phenylalanine that can be performed particularly well in an enzyme membrane reactor (EMR) are shown in reaction 5 and 6. The recently discovered enzyme phenylalanine dehydrogenase plays an important role. As can be seen, the reactions are coenzyme dependent and the production of L-phenylalanine is by reductive animation of phenylpyruvic add. Electrons can be transported from formic add to phenylpyruvic add so that two substrates have to be used formic add and an a-keto add phenylpyruvic add (reaction 5). Also electrons can be transported from an a-hydroxy add to form phenylpyruvic add which can be aminated so that only one substrate has to be used a-hydroxy acid phenyllactic acid (reaction 6). 

A typical example of these analytical systems is a manifold using bacterial luciferase for L-phenylalanine assay [228] developed with two separate nylon coils, as shown in Figure 3. The first one contained the specific L-phenylalanine dehydrogenase (L-PheDH) enzyme. 

Some enzymes with improved single amino acid specificity are commercially available. An example is phenylalanine dehydrogenase (EC 1.4.1.1), derived from bacterial sources, which acts on phenylalanine with the simultaneous conversion of NAD to NADH. Quantitation of the phenylalanine is based on determining the amount of NADH produced using standard procedures. In the direct methods, the absorbance at 340 nm is measured, whereas in the colorimetric methods, the reaction is coupled to an electron acceptor... 

Synthesis of Substituted Derivatives of L-Phenylalanine and of other Non-natural L-Amino Acids Using Engineered Mutants of Phenylalanine Dehydrogenase... 

We have used a series of biocatalysts produced by site-directed mutations at the active site of L-phenylalanine dehydrogenase (PheDH) of Bacillus sphaericus, which expand the substrate specificity range beyond that of the wild-type enzyme, to catalyse oxidoreduc-tions involving various non-natural L-amino acids. These may be produced by enantiose-lective enzyme-catalysed reductive amination of the corresponding 2-oxoacid. Since the reaction is reversible, these biocatalysts may also be used to effect a kinetic resolution of a D,L racemic mixture. ... 

Seah, S.Y.K., Britton, K.L., Rice, D.W., Asano, Y. and Engel, P.C., Single amino acid substitution in Bacillus sphacricus phenylalanine dehydrogenase dramatically increases its discrimination between phenylalanine and tyrosine substrates. Biochemistry, 2002, 41, 11390. 

Busca, P., Paradisi, E., Moynihan, E., Maguire, A.R. and Engel, P.C., Enantioselective synthesis of non-natural amino acids using phenylalanine dehydrogenases modified by site-directed mutagenesis. Org. Biomol. Chem., 2004, 2, 2684. 

L-Phenylalanine dehydrogenase in chiral L-amino acid synthesis 76... 

In a similar exercise with D-methionine, Findrik and Vasic-Racki used the D-AAO of Arthrobacter, and for the second-step conversion of oxoacid into L-amino acid, used L-phenylalanine dehydrogenase (L-PheDH), which has a sufficiently broad specificity to accept L-methionine and its corresponding oxoacid as substrates. Efficient quantitative conversion in this latter reaction requires recycling of the cofactor NAD into NADH, and for this the commercially available formate dehydrogenase (FDH) was used (Scheme 2). 

OCTANOL DEHYDROGENASE OCTOPINE DEHYDROGENASE PHENYLALANINE DEHYDROGENASE POLY(ADP-RIBOSE) SYNTHETASE (or, SYNTHASE)... 

PHENYLALANINE AMINOTRANSFERASE PHENYLALANINE AMMONIA-LYASE PHENYLALANINE DECARBOXYLASE PHENYLALANINE DEHYDROGENASE PHENYLALANINE MONOOXYGENASE PHENYLALANINE RACEMASE PHENYLALANINE AMINOTRANSFERASE AROMATIC AMINO ACID AMINOTRANSFERASE... 

PHENYLALANINE AMMONIA-LYASE DEHYDROALANINE BOROHYDRIDE REDUCTION PHENYLALANINE DECARBOXYLASE PHENYLALANINE DEHYDROGENASE Phenylalanine(histidine) aminotransferase, PHENYLALANINE AMINOTRANSFERASE PHENYLALANINE HYDROXYLASE (Phenylalanine Monooxygenase)... 

PHENYLALANINE DEHYDROGENASE PREPHENATE DEHYDRATASE PHENYLPYRUVATE SYNTHASE PHI (< or4))... 

Bacillus sphaericus phenylalanine dehydrogenase mutant (on celite)... 

HicDH = Hydroxycaproate dehydrogenase PheDH = Phenylalanine dehydrogenase Scheme 6.14 Enzymatic conversion of an a-hydroxy acid to an a-amino acid. 

J. J. Venit, L. J. Szarka, and R. N. Patel, Synthesis of allysine ethylene acetal using phenylalanine dehydrogenase from Thermoactinomyces intermedius, Enzyme Microb. Technol. 2000b, 26, 348-358. 

Reductive amination reactions of keto acids are performed with amino acid dehydrogenases. NAD-dependent leucine dehydrogenase from Bacillus sp. is of interest for the synthesis of (S)-fert.-leucine [15-17]]. This chiral compound has found widespread application in asymmetric synthesis and as a building block of biologically active substances. The enzyme can also be used for the chemoenzy-matic preparation of (S)-hydroxy-valine [18] and unnatural hydrophobic bran-ched-chain (S)-amino acids. NAD-dependent L-phenylalanine dehydrogenase from Rhodococcus sp. [19] has been used for the synthesis of L-homophenyl-alanine ((S)-2-Amino-4-phenylbutanoic acid) [9]. These processes with water-soluble substrates and products demonstrate that the use of coenzymes must not... 

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