Structure and biocatalytic scope of thermophilic flavin-dependent halogenase and flavin reductase enzymes

Org Biomol Chem. 2016 Oct 4;14(39):9354-9361. doi: 10.1039/c6ob01861k.

Abstract

Flavin-dependent halogenase (Fl-Hal) enzymes have been shown to halogenate a range of synthetic as well as natural aromatic compounds. The exquisite regioselectively of Fl-Hal enzymes can provide halogenated building blocks which are inaccessible using standard halogenation chemistries. Consequently, Fl-Hal are potentially useful biocatalysts for the chemoenzymatic synthesis of pharmaceuticals and other valuable products, which are derived from haloaromatic precursors. However, the application of Fl-Hal enzymes, in vitro, has been hampered by their poor catalytic activity and lack of stability. To overcome these issues, we identified a thermophilic tryptophan halogenase (Th-Hal), which has significantly improved catalytic activity and stability, compared with other Fl-Hal characterised to date. When used in combination with a thermostable flavin reductase, Th-Hal can efficiently halogenate a number of aromatic substrates. X-ray crystal structures of Th-Hal, and the reductase partner (Th-Fre), provide insights into the factors that contribute to enzyme stability, which could guide the discovery and engineering of more robust and productive halogenase biocatalysts.

MeSH terms

  • Bacillus subtilis / enzymology
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism
  • Catalytic Domain
  • Circular Dichroism
  • Crystallography, X-Ray
  • Enzyme Stability
  • FMN Reductase / chemistry*
  • FMN Reductase / metabolism*
  • Kinetics
  • Models, Molecular
  • Oxidoreductases / chemistry*
  • Oxidoreductases / metabolism*
  • Streptomyces / enzymology
  • Substrate Specificity
  • Transition Temperature

Substances

  • Bacterial Proteins
  • Oxidoreductases
  • tryptophan halogenase
  • FMN Reductase