title: How Formaldehyde Inhibits Hydrogen Evolution by [FeFe]-Hydrogenases: Determination by ¹³C ENDOR of Direct Fe-C Coordination and Order of Electron and Proton Transfers.
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-(13)C 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.
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: Andreas
authors: A
authors: Bachmeier
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: Julian
authors: J
authors: Esselborn
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: Suzannah V
authors: SV
authors: Hexter
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: Tobias
authors: T
authors: Krämer
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: Kathrin
authors: K
authors: Klein
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: Thomas
authors: T
authors: Happe
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: John E
authors: JE
authors: McGrady
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: William K
authors: WK
authors: Myers
authors: †Inorganic Chemistry Laboratory and ‡Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.|§Lehrstuhl für Biochemie der Pflanzen, AG Photobiotechnologie and ∥Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, 44801 Bochum, Germany.
authors: Fraser A
authors: FA
authors: Armstrong
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005557:Formaldehyde / Q000494:pharmacology*; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D011522:Protons; D011789:Quantum Theory
chemical_list: D004791:Enzyme Inhibitors; D011522:Protons; D005557:Formaldehyde; D006859:Hydrogen; D006864:Hydrogenase