How formaldehyde inhibits hydrogen evolution by [FeFe]-hydrogenases: Determination by 13C ENDOR of direct Fe-C coordination and order of electron and proton transfers

Andreas Bachmeier, Julian Esselborn, Suzannah V. Hexter, Tobias Krämer, Kathrin Klein, Thomas Happe, John E. McGrady, William K. Myers, Fraser A. Armstrong

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5 Citations (Scopus)

Abstract

Formaldehyde (HCHO), a strong electrophile and a rapid and reversible inhibitor of hydrogen production by [FeFe]-hydrogenases, is used to identify the point in the catalytic cycle at which a highly reactive metal-hydrido species is formed. Investigations of the reaction of Chlamydomonas reinhardtii [FeFe]-hydrogenase with formaldehyde using pulsed-EPR techniques including electron-nuclear double resonance spectroscopy establish that formaldehyde binds close to the active site. Density functional theory calculations support an inhibited super-reduced state having a short Fe-13C bond in the 2Fe subsite. The adduct forms when HCHO is available to compete with H+ transfer to a vacant, nucleophilic Fe site: had H+ transfer already occurred, the reaction of HCHO with the Fe-hydrido species would lead to methanol, release of which is not detected. Instead, Fe-bound formaldehyde is a metal-hydrido mimic, a locked, inhibited form analogous to that in which two electrons and only one proton have transferred to the H-cluster. The results provide strong support for a mechanism in which the fastest pathway for H2 evolution involves two consecutive proton transfer steps to the H-cluster following transfer of a second electron to the active site.

Original languageEnglish
Pages (from-to)5381-5389
Number of pages9
JournalJournal of the American Chemical Society
Volume137
Issue number16
DOIs
Publication statusPublished - 29 Apr 2015

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

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    Bachmeier, A., Esselborn, J., Hexter, S. V., Krämer, T., Klein, K., Happe, T., McGrady, J. E., Myers, W. K., & Armstrong, F. A. (2015). How formaldehyde inhibits hydrogen evolution by [FeFe]-hydrogenases: Determination by 13C ENDOR of direct Fe-C coordination and order of electron and proton transfers. Journal of the American Chemical Society, 137(16), 5381-5389. https://doi.org/10.1021/ja513074m