On the Structure and Reaction Mechanism of Human Acireductone Dioxygenase

Anna Miłaczewska, Ewa Kot, José A. Amaya, Thomas M. Makris, Marcin Zając, Józef Korecki, Aleksandr Chumakov, Bartosz Trzewik, Sylwia Kędracka-Krok, Władek Minor, Maksymilian Chruszcz, Tomasz Borowski

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22 Scopus citations

Abstract

Acireductone dioxygenase (ARD) is an intriguing enzyme from the methionine salvage pathway that is capable of catalysing two different oxidation reactions with the same substrate depending on the type of the metal ion in the active site. To date, the structural information regarding the ARD–acireductone complex is limited and possible reaction mechanisms are still under debate. The results of joint experimental and computational studies undertaken to advance knowledge about ARD are reported. The crystal structure of an ARD from Homo sapiens was determined with selenomethionine. EPR spectroscopy suggested that binding acireductone triggers one protein residue to dissociate from Fe2+, which allows NO (and presumably O2) to bind directly to the metal. Mössbauer spectroscopic data (interpreted with the aid of DFT calculations) was consistent with bidentate binding of acireductone to Fe2+ and concomitant dissociation of His88 from the metal. Major features of Fe vibrational spectra obtained for the native enzyme and upon addition of acireductone were reproduced by QM/MM calculations for the proposed models. A computational (QM/MM) study of the reaction mechanisms suggests that Fe2+ promotes O−O bond homolysis, which elicits cleavage of the C1−C2 bond of the substrate. Higher M3+/M2+ redox potentials of other divalent metals do not support this pathway, and instead the reaction proceeds similarly to the key reaction step in the quercetin 2,3-dioxygenase mechanism.

Original languageEnglish
Pages (from-to)5225-5237
Number of pages13
JournalChemistry - A European Journal
Volume24
Issue number20
DOIs
StatePublished - 6 Apr 2018
Externally publishedYes

Keywords

  • EPR spectroscopy
  • Mössbauer spectroscopy
  • acireductone dioxygenase
  • protein structures
  • reaction mechanisms

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