Vincent Kylie A, Parkin Alison, Lenz Oliver, Albracht Simon P J, Fontecilla-Camps Juan C, Cammack Richard, Friedrich Bärbel, Armstrong Fraser A
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.
J Am Chem Soc. 2005 Dec 28;127(51):18179-89. doi: 10.1021/ja055160v.
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.
本文描述了一种新策略，用于定量比较氢化酶耐受暴露于氧气和缺氧氧化条件的能力。使用蛋白质膜伏安法，已测量了一系列嗜温微生物的酶对这些挑战（热力学电位和反应速率）的固有敏感性。在没有氧气的情况下，所有氢化酶在高于H⁺/H₂氧化还原对的各种电位下都会发生可逆失活，因此H₂氧化活性仅限于特定的“电位窗口”。与氧气的反应差异很大；来自厌氧生物脱硫弧菌ATCC 7757的[FeFe] - 氢化酶会被氧气不可逆地破坏，只有在厌氧氧化状态下暴露于氧气时才能存活（因此提供了保护）。相比之下，需氧生物真养产碱菌的膜结合[NiFe] - 氢化酶即使在周转过程中也能与氧气发生可逆反应，并在有氧气存在的情况下继续催化H₂氧化。
