Amino Acid Isomerization in the Production of l -Phenylalanine from d -Phenylalanine by Bacteria

Abstract

To establish an advantageous method for the production of l -amino acids, microbial isomerization of d - and dl -amino acids to l -amino acids was studied. Screening experiments on a number of microorganisms showed that cell suspensions of Pseudomonas fluorescens and P. miyamizu were capable of isomerizing d - and dl -phenylalanines to l -phenylalanine. Various conditions suitable for isomerization by these organisms were investigated. Cells grown in a medium containing d -phenylalanine showed highest isomerization activity, and almost completely converted d - or dl -phenylalanine into l -phenylalanine within 24 to 48 hr of incubation. Enzymatic studies on this isomerizing system suggested that the isomerization of d - or dl -phenylalanine is not catalyzed by a single enzyme, “amino acid isomerase,” but the conversion proceeds by a two step system as follows: d -pheylalanine is oxidized to phenylpyruvic acid by d -amino acid oxidase, and the acid is converted to l -phenylalanine by transamination or reductive amination.

Cytotoxic and Antihaptotactic Beauvericin Analogues from Precursor-Directed Biosynthesis with the Insect Pathogen Beauveria bassiana ATCC 7159

“…Feeding with enantiomerically pure (>99%) l -3-fluorophenylalanine and d -3-fluorophenylalanine were equally efficient in producing 5 – 7 , in apparent contradiction to the above result and to those of Peeters et al, who have shown that purified beauvericin synthetase (albeit from a different B. bassiana strain) is unable to utilize d -Phe for the synthesis of beauvericin ( 1 ). However, in vivo interconversion of d and l amino acids, including Phe, using isomerase or racemase, or an oxidase–transaminase pair of enzymes, is well-documented in microorganisms. Another precursor analogue, dl -2-fluorophenylalanine, was similarly found to be inhibitory to fungal growth in concentrations exceeding 1.0 mM.…”

Catalytic Deracemization Reactions

“…The history of deracemization started from 1965, when Chibata et al found that cell suspension of Pseudomonas miyamizu was capable of converting racemic phenylalanine into d -phenylalanine completely . Detailed studies revealed a two-step process involving enzymatic oxidation and transamination.…”

“…The first example on this category was realized in 1965 through biocatalysis thanks to the compartment effect of enzyme in the modulating redox process. 12 However, it was not until 2005 that chemo-catalysis was successfully applied in deracemization through a one-pot two-step dehydrogenation and hydrogenation of alcohols. 13 Notable extension to nonalcoholic substrates has since been developed by the works of Toste, 14 Zhou, 15 Liu 16 et al In these chemical energy-driven deracemizations, stoichiometric amounts of redox reagents are sacrificed, diminishing the overall reaction economy.…”

“…Most successes along this line were met with redox-labile substrates such as alcohols and amines. The first example on this category was realized in 1965 through biocatalysis thanks to the compartment effect of enzyme in the modulating redox process . However, it was not until 2005 that chemo-catalysis was successfully applied in deracemization through a one-pot two-step dehydrogenation and hydrogenation of alcohols .…”

“…The history of deracemization started from 1965, when Chibata et al found that cell suspension of Pseudomonas miyamizu was capable of converting racemic phenylalanine into D-phenylalanine completely. 12 Detailed studies revealed a two-step process involving enzymatic oxidation and transamination. Living cells including bacteria, fungi, yeasts, and plants were subsequently reported to be viable for deracemization of amines and alcohols.…”