Electron paramagnetic resonance detection of intermediates in the enzymatic cycle of an extradiol dioxygenase.
Electron paramagnetic resonance detection of intermediates in the enzymatic cycle of an extradiol dioxygenase.
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DOI：
10.1021/ja8052255
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发表时间：
2008-11-05
影响因子：
15
通讯作者：
Hendrich, Michael P.
中科院分区：
文献类型：
--
作者：
Gunderson, William A.;Zatsman, Anna I.;Emerson, Joseph P.;Farquhar, Erik R.;Que, Lawrence, Jr.;Lipscomb, John D.;Hendrich, Michael P.
外源性儿茶酚双加氧酶催化底物芳香环的裂解，结合O2中的两个氧原子。这些酶在自然界中对于从芳香族化合物中回收大量碳是重要的。催化中心含有铁或锰，由两个组氨酸和一个谷氨酸或天冬氨酸残基组成的三联体配位。以往的研究表明，Fe(II)和Mn(II)可以在不同生物体的酶中互换，从而催化相似的底物反应。结合定量电子顺磁共振光谱和快速冷冻−猝灭实验，我们可以在酶翻转其天然底物时跟踪四种不同锰物种的浓度，包括催化循环中的关键金属中间体。观察到两种中间体：一种是锰(III)-自由基物种，它是锰超氧化物或锰底物自由基；另一种是参与循环限速步骤的独特的锰(II)物种，它可能是锰-烷基过氧基。
Extradiol catecholic dioxygenases catalyze the cleavage of the aromatic ring of the substrate with incorporation of both oxygen atoms from O2. These enzymes are important in nature for the recovery of large amounts of carbon from aromatic compounds. The catalytic site contains either Fe or Mn coordinated by a facial triad of two His and one Glu or Asp residues. Previous studies have shown that Fe(II) and Mn(II) can be interchanged in enzymes from different organisms to catalyze similar substrate reactions. In combination, quantitative electron paramagnetic resonance spectroscopy and rapid freeze−quench experiments allow us to follow the concentrations of four different Mn species, including key metal intermediates in the catalytic cycle, as the enzyme turns over its natural substrate. Two intermediates are observed: a Mn(III)-radical species which is either Mn-superoxide or Mn-substrate radical, and a unique Mn(II) species which is involved in the rate-limiting step of the cycle and may be Mn-alkylperoxo.
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影响因子：
15
作者：
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通讯作者：
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影响因子：
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