Multiple forms of the catalytic centre, Cu-z, in the enzyme nitrous oxide reductase from Paracoccus pantotrophus

Tim Rasmussen, B C Berks, J N Butt, A J Thomson

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Abstract

Nitrous oxide reductase catalyses the reduction of nitrous oxide to dinitrogen at a unique tetranuclear copper site, called Cu-z, which has a central inorganic sulphide ligand. Limited incubation with oxygen during the preparation of nitrous oxide reductase from Paracoccus pantotrophus results in changed redox properties of the catalytic centre by comparison with anaerobic preparations. While the anaerobically purified enzyme has a cataltic centre which performs a single electron step at a midpoint potential of E-m = +60 mV versus the standard hydrogen electrode (n = 1) the altered centre shows no redox change under similar experimental conditions. Spectroscopic properties of this 'redox fixed' centre are similar to spectra of the reduced redox active' form of Cu-z, although the positions and intensities of a number of transitions are changed in the optical spectrum. These observations are interpreted in terms of two forms of the catalytic centre. called Cu-z and Cu-z*. The structural relationship between these forms is unclear. EPR and magnetic circular dichroism spectra suggest that the basic Cu4S structure is common to both. Curiously. steady-state activity of the aerobic enzyme preparation is slightly increased despite the fact the catalytic centre does not undergo detectable redox changes.

Original languageEnglish
Pages (from-to)807-815
Number of pages9
JournalBiochemical Journal
Volume364
Issue number3
Publication statusPublished - 15 Jun 2002

Keywords

  • copper
  • denitrification
  • magnetic circular dichroism
  • oxygen sensitivity
  • redox titration
  • RESONANCE RAMAN-SPECTROSCOPY
  • ELECTRON-TRANSFER CENTER
  • PSEUDOMONAS-STUTZERI
  • CYTOCHROME-C
  • A CENTER
  • THIOSPHAERA-PANTOTROPHA
  • MULTICOPPER ENZYME
  • N2O REDUCTASE
  • COPPER SITES
  • GROUND-STATE
  • redox titration
  • RESONANCE RAMAN SPECTROSCOPY
  • ELECTRON TRANSFER CENTER
  • PSEUDOMONAS STUTZERI
  • THIOSPHAERA PANTOTROPHA
  • GROUND STATE

Cite this

Rasmussen, T., Berks, B. C., Butt, J. N., & Thomson, A. J. (2002). Multiple forms of the catalytic centre, Cu-z, in the enzyme nitrous oxide reductase from Paracoccus pantotrophus. Biochemical Journal, 364(3), 807-815.