Details

Autor(en) / Beteiligte

• Lubitz, Wolfgang
• van Gastel, Maurice
• Gärtner, Wolfgang
• Sigel, Roland K. O
• Sigel, Helmut
• Sigel, Astrid

Titel

Nickel Iron Hydrogenases

Ist Teil von

• Nickel and Its Surprising Impact in Nature, 2007, p.279-322

Ort / Verlag

Chichester, UK: John Wiley & Sons, Ltd

Erscheinungsjahr

2007

Link zum Volltext

Quelle

Wiley-Blackwell Online Books - All Titles (includes Withdrawn titles)

Beschreibungen/Notizen

• Recent research in the field of [NiFe] hydrogenases is reviewed. An introduction is given to the biochemistry and molecular biology of this enzyme including its constitution, cellular location, the encoding genes, and the maturation pathways. Site‐directed mutations are discussed that were constructed to alter the active site, the electron transfer or proton translocation pathways or the gas channel(s) of this protein. The crystallization and X‐ray structure analyses of [NiFe] hydrogenase from various species are presented, yielding a detailed structural picture of the enzyme, in particular of the bimetallic (NiFe) center and its unusual ligand sphere. The various redox states of the catalytic cycle as well as the activation and deactivation processes are described. These can be followed by FTIR spectroscopy using shifts of the vibrational frequencies of the CN and CO ligands attached to the Fe of the active site. Spectroelectrochemical methods allow the determination of the midpoint potentials, pH dependences, and activation barriers of the reactions. Details of the electronic structure of the active site are revealed by EPR spectroscopy and related techniques such as ENDOR and ESEEM/HYSCORE. These methods are sensitive tools for detecting the magnetic interactions of paramagnetic states which occur in the reactions. Density functional theory calculations are shown to be valuable to determine spectroscopic parameters of the intermediates of the enzymatic cycle and relate them to structure and function. A new technique, protein film voltammetry, is discussed that has greatly contributed to a better understanding of this enzyme, in particular with regard to the potential‐ and pH‐dependent reaction with the substrate (H 2 /H + ) and gases (e.g., O 2 , CO) that inhibit the enzyme. Based on the various data a large number of intermediates could be identified and characterized for the [NiFe] hydrogenase. Finally, the mechanisms proposed in the literature for the activation and deactivation of the enzyme and the catalytic cycle are discussed.