Structure of the key species in the enzymatic oxidation of methane to methanol.
Structure of the key species in the enzymatic oxidation of methane to methanol.
复制标题
甲烷酶氧化甲醇的酶促氧化中的关键物种的结构。
DOI：
10.1038/nature14160
复制
发表时间：
2015-02-19
期刊：
影响因子：
64.8
通讯作者：
Proshlyakov, Denis A.
中科院分区：
文献类型：
--
作者：
Banerjee, Rahul;Proshlyakov, Yegor;Lipscomb, John D.;Proshlyakov, Denis A.
甲烷单加氧酶（MMO）催化甲烷氧化细菌中甲烷向甲醇的O2依赖性转化，从而防止每年约10亿吨这种强效温室气体的大气排放。可溶形式MMO（sMMO）的关键反应循环中间体被称为化合物Q（Q）。Q含有一个独特的双核FeIV簇，它与甲烷反应，打破一个异常强大的105 kcal mol−1 C-H键，并插入一个氧原子。除了在MMO的颗粒形式中发现的生物氧化剂之外，没有其他生物氧化剂能够进行这种催化。尽管有许多光谱、计算和合成模型研究，Q的结构仍然存在争议。一个明确的结构分配，可以从共振拉曼振动光谱，但尽管在过去的二十年的努力，没有振动光谱的Q尚未获得。在这里，我们报告的核心结构的Q和以下产品的复杂性，化合物T，使用时间分辨共振拉曼光谱（TR 3）。TR 3允许通过其独特的振动签名，通过延长信号平均短寿命的物种的中间体的指纹。我们报告明确的证据表明，Q具有双-μ-氧代金刚石核结构，并表明，这两个桥氧起源于O2。这一观察结果有力地支持了O-O键断裂的均裂机制。我们还表明，T保留一个氧原子从O2作为一个桥接配体，而其他氧原子被纳入到产品。捕获Q的极端氧化电位对于生物修复和开发基于甲烷的替代燃料和化学工业原料的合成方法具有极大的当代兴趣。从这里报道的结构中洞察Q的形成和反应性是利用这种潜力的重要一步。
Methane monooxygenase (MMO) catalyses the O2-dependent conversion of methane to methanol in methanotrophic bacteria, thereby preventing the atmospheric egress of approximately one billion tons of this potent greenhouse gas annually. The key reaction cycle intermediate of the soluble form of MMO (sMMO) is termed compound Q (Q). Q contains a unique dinuclear FeIV cluster that reacts with methane to break an exceptionally strong 105 kcal mol−1 C-H bond and insert one oxygen atom. No other biological oxidant, except that found in the particulate form of MMO, is capable of such catalysis. The structure of Q remains controversial despite numerous spectroscopic, computational and synthetic model studies. A definitive structural assignment can be made from resonance Raman vibrational spectroscopy but, despite efforts over the past two decades, no vibrational spectrum of Q has yet been obtained. Here we report the core structures of Q and the following product complex, compound T, using time-resolved resonance Raman spectroscopy (TR3). TR3 permits fingerprinting of intermediates by their unique vibrational signatures through extended signal averaging for short-lived species. We report unambiguous evidence that Q possesses a bis-μ-oxo diamond core structure and show that both bridging oxygens originate from O2. This observation strongly supports a homolytic mechanism for O-O bond cleavage. We also show that T retains a single oxygen atom from O2 as a bridging ligand, while the other oxygen atom is incorporated into the product. Capture of the extreme oxidizing potential of Q is of great contemporary interest for bioremediation and the development of synthetic approaches to methane-based alternative fuels and chemical industry feedstocks. Insight into the formation and reactivity of Q from the structure reported here is an important step towards harnessing this potential.
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