Mono‐iron hydrogenase ([Fe]‐hydrogenase) reversibly catalyzes the transfer of a hydride ion from H₂ to methenyltetrahydromethanopterin (methenyl‐H₄MPT⁺) to form methylene‐H₄MPT. Its iron guanylylpyridinol (FeGP) cofactor plays a key role in H₂ activation. Evidence is presented for O₂ sensitivity of [Fe]‐hydrogenase under turnover conditions in the presence of reducing substrates, methylene‐H₄MPT or methenyl‐H₄MPT⁺/H₂. Only then, H₂O₂ is generated, which decomposes the FeGP cofactor; as demonstrated by spectroscopic analyses and the crystal structure of the deactivated enzyme. O₂ reduction to H₂O₂ requires a reductant, which can be a catalytic intermediate transiently formed during the [Fe]‐hydrogenase reaction. The most probable candidate is an iron hydride species; its presence has already been predicted by theoretical studies of the catalytic reaction. The findings support predictions because the same type of reduction reaction is described for ruthenium hydride complexes that hydrogenate polar compounds.

中文翻译：

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还原性底物存在下[Fe]-加氢酶的双氧敏感性

单铁加氢酶（[Fe]-加氢酶）可逆地催化氢离子从H ₂转移至亚甲基四氢甲蝶呤（methenyl-H ₄ MPT ⁺），形成亚甲基-H ₄ MPT。其胍基铁吡啶铁（FeGP）辅因子在H ₂活化中起关键作用。提出了在存在还原性底物，亚甲基-H ₄ MPT或亚甲基-H ₄ MPT ⁺ / H ₂的情况下，在周转条件下[Fe]-加氢酶的O ₂敏感性的证据。只有这样，H ₂ O ₂产生，分解FeGP辅因子；如通过光谱分析和失活酶的晶体结构所证明的。O ₂还原为H ₂ O ₂需要还原剂，它可以是[Fe]-加氢酶反应过程中短暂形成的催化中间体。最可能的候选物质是氢化铁。通过催化反应的理论研究已经预测了其存在。该发现支持预测，因为描述了氢化极性化合物的氢化钌配合物的相同类型的还原反应。