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Ring-cleaving dioxygenases with a cupin fold.

Susanne Fetzner1

  • 1Institute of Molecular Microbiology and Biotechnology, Westfalian Wilhelms University Münster, Münster, Germany. fetzner@uni-muenster.de

Applied and Environmental Microbiology
|January 31, 2012
PubMed
Summary
This summary is machine-generated.

Ring-cleaving dioxygenases, part of the cupin superfamily, degrade aromatic compounds. Some, like quercetinase, use various metal ions, suggesting substrate positioning is key, not just electron transfer.

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Area of Science:

  • Biochemistry
  • Microbial Metabolism
  • Enzymology

Background:

  • Ring-cleaving dioxygenases are crucial for aerobic microbial degradation of aromatic compounds.
  • Pathways often involve catecholic intermediates cleaved by intradiol or extradiol dioxygenases.
  • Alternative pathways utilize noncatecholic hydroxy-substituted aromatic carboxylic acids.

Purpose of the Study:

  • To investigate the catalytic mechanisms of cupin-type ring-cleaving dioxygenases.
  • To explore the role of the active-site metal ion in these enzymes.
  • To understand the function of quercetinase in flavonol degradation.

Main Methods:

  • Characterization of cupin-type dioxygenases.
  • Analysis of conserved amino acid motifs and metal ion coordination.
  • Investigation of quercetinase activity and metal ion usage.
  • Comparison with canonical extradiol dioxygenases.

Main Results:

  • Cupin-type dioxygenases feature a conserved β-barrel fold and metal-binding motifs.
  • Most use Fe(II) and proposed mechanisms resemble extradiol dioxygenases, involving electron transfer.
  • Bacterial quercetinases can utilize various metal ions, indicating metal redox properties are less critical.
  • The active-site metal may primarily stabilize substrates and transition states.

Conclusions:

  • The catalytic mechanism of cupin-type dioxygenases is diverse, with metal ion roles varying.
  • Quercetinase catalysis might involve direct electron transfer from substrate to O(2), with the metal aiding substrate positioning.
  • Further research into these dioxygenases can illuminate microbial degradation pathways and enzyme evolution.