Phenylalanine ammonia-lyase: The use of its broad substrate specificity for mechanistic investigations and biocatalysis - Synthesis of L-arylalanines

Andreas Gloge, Jerzy Zoń, Ágnes Kövári, László Poppe, János Rétey

Research output: Contribution to journalArticle

74 Citations (Scopus)

Abstract

Several fluoro-and chlorophenylalanines were found to be good substrates of phenylalanine ammonialyase (PAL/EC 4.3.1.5) from parsley. The enantiomerically pure L-amino acids were obtained in good yields by reaction of the corresponding cinnamic acids with 5M ammonia solution (buffered to pH 10) in the presence of PAL. The kinetic constants for nine different fluoro-and chlorophenylalanines do not provide a rigorous proof for but are consistent with the previously proposed mechanism comprising an electrophilic attack of the methylidene-imidazolone cofactor of PAL at the aromatic nucleus as a first chemical step. In the resulting Friedel-Crafts-type σ complex the β-protons are activated for abstraction and consequently the pro-S is abstracted by an enzymic base. Results from semi-empirical calculations combined with a proposed partial active site model showed a correlation between the experimental kinetic constants and the change in polarization of the pro-S Cβ-H bond and heat of formation of the σ complexes, thus making the electrophilic attack at the neutral aromatic ring plausible. Furthermore, while 5-pyrimidinylalanine was found to be a moderately good substrate of PAL, 2-pyrimidinylalanine was an inhibitor.

Original languageEnglish
Pages (from-to)3386-3390
Number of pages5
JournalChemistry - A European Journal
Volume6
Issue number18
DOIs
Publication statusPublished - Sep 15 2000

Keywords

  • Chemoenzymatic synthesis
  • Enzyme inhibitors
  • Enzyme mechanism
  • Halogenated l-phenylalanines
  • Lyases

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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