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.

中文翻译：

---

外二醇双加氧酶酶促循环中中间体的电子顺磁共振检测

Extradiol 儿茶酚双加氧酶催化底物芳环的裂解，同时从 O2 中引入两个氧原子。这些酶在自然界中对于从芳香族化合物中回收大量碳很重要。催化位点包含 Fe 或 Mn，由两个 His 和一个 Glu 或 Asp 残基的面部三元组协调。先前的研究表明，Fe(II) 和 Mn(II) 可以在来自不同生物体的酶中互换，以催化类似的底物反应。结合定量电子顺磁共振波谱和快速冷冻淬灭实验，我们可以跟踪四种不同 Mn 物种的浓度，包括催化循环中的关键金属中间体，因为酶翻转其天然底物。观察到两个中间体：