Activation Thermodynamics and H/D Kinetic Isotope Effect of the Hox to HredH+ Transition in [FeFe] Hydrogenase

J Am Chem Soc. 2017 Sep 20;139(37):12879-12882. doi: 10.1021/jacs.7b04216. Epub 2017 Sep 6.

Abstract

Molecular complexes between CdSe nanocrystals and Clostridium acetobutylicum [FeFe] hydrogenase I (CaI) enabled light-driven control of electron transfer for spectroscopic detection of redox intermediates during catalytic proton reduction. Here we address the route of electron transfer from CdSe→CaI and activation thermodynamics of the initial step of proton reduction in CaI. The electron paramagnetic spectroscopy of illuminated CdSe:CaI showed how the CaI accessory FeS cluster chain (F-clusters) functions in electron transfer with CdSe. The Hox→HredH+ reduction step measured by Fourier-transform infrared spectroscopy showed an enthalpy of activation of 19 kJ mol-1 and a ∼2.5-fold kinetic isotope effect. Overall, these results support electron injection from CdSe into CaI involving F-clusters, and that the Hox→HredH+ step of catalytic proton reduction in CaI proceeds by a proton-dependent process.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cadmium Compounds / chemistry
  • Cadmium Compounds / metabolism*
  • Clostridium acetobutylicum / enzymology
  • Deuterium Exchange Measurement
  • Electron Transport
  • Hydrogenase / chemistry
  • Hydrogenase / metabolism*
  • Iron-Sulfur Proteins / chemistry
  • Iron-Sulfur Proteins / metabolism*
  • Kinetics
  • Molecular Conformation
  • Nanostructures / chemistry
  • Oxidation-Reduction
  • Selenium Compounds / chemistry
  • Selenium Compounds / metabolism*
  • Spectroscopy, Fourier Transform Infrared
  • Thermodynamics*

Substances

  • Cadmium Compounds
  • Iron-Sulfur Proteins
  • Selenium Compounds
  • cadmium selenide
  • iron hydrogenase
  • Hydrogenase