title: Electrochemical definitions of O2 sensitivity and oxidative inactivation in hydrogenases.
abstract: A new strategy is described for comparing, quantitatively, the ability of hydrogenases to tolerate exposure to O2 and anoxic oxidizing conditions. Using protein film voltammetry, the inherent sensitivities to these challenges (thermodynamic potentials and rates of reactions) have been measured for enzymes from a range of mesophilic microorganisms. In the absence of O2, all the hydrogenases undergo reversible inactivation at various potentials above that of the H+/H2 redox couple, and H2 oxidation activities are thus limited to characteristic "potential windows". Reactions with O2 vary greatly; the [FeFe]-hydrogenase from Desulfovibrio desulfuricans ATCC 7757, an anaerobe, is irreversibly damaged by O2, surviving only if exposed to O2 in the anaerobically oxidized state (which therefore affords protection). In contrast, the membrane-bound [NiFe]-hydrogenase from the aerobe, Ralstonia eutropha, reacts reversibly with O2 even during turnover and continues to catalyze H2 oxidation in the presence of O2.
authors.affiliation: Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.
authors.forename: Kylie A
authors.initials: KA
authors.lastname: Vincent
authors.forename: Alison
authors.initials: A
authors.lastname: Parkin
authors.forename: Oliver
authors.initials: O
authors.lastname: Lenz
authors.forename: Simon P J
authors.initials: SP
authors.lastname: Albracht
authors.forename: Juan C
authors.initials: JC
authors.lastname: Fontecilla-Camps
authors.forename: Richard
authors.initials: R
authors.lastname: Cammack
authors.forename: Bärbel
authors.initials: B
authors.lastname: Friedrich
authors.forename: Fraser A
authors.initials: FA
authors.lastname: Armstrong
mesh_terms: D000693:Anaerobiosis; D004563:Electrochemistry; D004789:Enzyme Activation; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D010100:Oxygen