title: CuIand H2O2Inactivate and FeIIInhibits [Fe]-Hydrogenase at Very Low Concentrations.
abstract: [Fe]-Hydrogenase (Hmd) catalyzes reversible hydride transfer from H2. It harbors an iron-guanylylpyridinol as a cofactor with an FeIIthat is ligated to one thiolate, two COs, one acyl-C, one pyridinol-N, and solvent. Here, we report that CuIand H2O2inactivate Hmd (half-maximal rates at 1 μM CuIand 20 μM H2O2) and that FeIIinhibits the enzyme with very high affinity (Ki=40 nM). Infrared and EPR studies together with competitive inhibition studies with isocyanide indicated that CuIexerts its inhibitory effect most probably by binding to the active site iron-thiolate ligand. Using the same methods, it was found that H2O2binds to the active-site iron at the solvent-binding site and oxidizes FeIIto FeIII. Also it was shown that FeIIreversibly binds away from the active site iron, with binding being competitive to the organic hydride acceptor; this inhibition is specific for FeIIand is reminiscent of that for the [FeFe]-hydrogenase second iron, which specifically interacts with H2.
authors.affiliation: Max-Planck-Institute für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse 10, 35043 Marburg (Germany).
authors.forename: Ryota
authors.initials: R
authors.lastname: Hidese
authors.affiliation: Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany).
authors.forename: Kenichi
authors.initials: K
authors.lastname: Ataka
authors.affiliation: Max Planck Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr (Germany).
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.affiliation: Max-Planck-Institute für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse 10, 35043 Marburg (Germany).|PRESTO, Japan Science and Technology Agency (JST), Saitama 332-0012 (Japan).
authors.forename: Seigo
authors.initials: S
authors.lastname: Shima
keywords: EPR spectroscopy; IR spectroscopy; hydrogenases; inhibitors; iron-guanylylpyridinol cofactor