The reaction mechanism of iron and manganese superoxide dismutases studied by theoretical calculations

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We have studied the detailed reaction mechanism of iron and manganese superoxide dismutase with density functional calculations on realistic active-site models, with large basis sets and including solvation, zero-point, and thermal effects. The results indicate that the conversion of O-2(-) to O-2 follows an associative mechanism, with O-2 directly binding to the metal, followed by the protonation of the metal-bound hydroxide ion, and the dissociation of O-3(2). All these reaction steps are exergonic. Likewise, we suggest that the conversion of O-2(-) to H2O2 follows an at least a partly second-sphere pathway. There are small differences in the preferred oxidation and spin states, as well as in the geometries, of Fe and Mn, but these differences have little influence on the energetics, and therefore on the reaction mechanism of the two types of superoxide dismutases. For example, the two metals have very similar reduction potentials in the active-site models, although they differ by 0.7 V in water solution. The reaction mechanisms and spin states seem to have been designed to avoid spin conversions or to facilitate them by employing nearly degenerate spin states. (c) 2006 Wiley Periodicals, Inc.


  • Lubomir Rulisek
  • Kasper Jensen
  • Kristoffer Lundgren
  • Ulf Ryde
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Theoretical Chemistry


  • superoxide dismutase, iron, manganese, reaction mechanisms
Original languageEnglish
Pages (from-to)1398-1414
JournalJournal of Computational Chemistry
Issue number12
Publication statusPublished - 2006
Publication categoryResearch

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Theoretical Chemistry (S) (011001039)