Microbial ethylene-forming enzyme (EFE) converts the C3-C4 fragment of the ubiquitous primary metabolite, 2-oxoglutarate (2OG), to its namesake alkene product. This reaction is very different from the simple decarboxylation of 2OG to succinate promoted by related enzymes and has inspired disparate mechanistic hypotheses. We show that EFE produces stereochemically random (equal cis and trans) 1,2-[²H₂]-ethylene from (3S,4R)-[²H₂]-2OG, appends an oxygen from O₂ upon the C1-derived (bi)carbonate, and can be diverted to ω-hydroxylated monoacid products by modifications to 2OG or the enzyme. These results implicate an unusual radical-polar hybrid mechanism involving iron(II)-coordinated acylperoxycarbonate and alkylcarbonate intermediates. The mechanism explains how EFE accesses a high-energy carboxyl radical to initiate its fragmentation cascade, and it hints at new capabilities of 2OG-dependent enzymes that may await discovery and exploitation.

中文翻译：

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铁加氧酶从 2-酮戊二酸中切除乙烯的混合自由基-极性途径

微生物乙烯形成酶 (EFE) 将普遍存在的初级代谢物 2-酮戊二酸 (2OG) 的 C3-C4 片段转化为其同名的烯烃产物。该反应与相关酶促进的 2OG 到琥珀酸的简单脱羧反应非常不同，并引发了不同的机制假设。我们表明 EFE从 ( 3S,4R )-[ ² H _{2 ]-2OG 产生立体化学随机（等于顺式和反式）1,2-[} ² H _{2 ]-乙烯，从 O 2}中附加一个氧在 C1 衍生的 (bi)carbonate 上，并且可以通过对 2OG 或酶的修饰转移到 ω-羟基化的单酸产物。这些结果暗示了一种不寻常的自由基-极性混合机制，涉及铁 (II) 配位的酰基过氧碳酸酯和烷基碳酸酯中间体。该机制解释了 EFE 如何访问高能羧基自由基以启动其碎片级联反应，并暗示可能等待发现和利用的 2OG 依赖性酶的新功能。