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

Lubomír Rulíšek, Kasper Planeta Kepp, Kristoffer Lundgren, Ulf Ryde

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

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.
Original languageEnglish
JournalJournal of Computational Chemistry
Volume27
Issue number12
Pages (from-to)1398-1414
ISSN0192-8651
DOIs
Publication statusPublished - 2006
Externally publishedYes

Keywords

  • Reaction mechanisms
  • Iron
  • Manganese
  • Superoxide dismutase

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