O–H Activation by an Unexpected Ferryl Intermediate during Catalysis by 2-Hydroxyethylphosphonate Dioxygenase

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• 作者：Spencer C. Peck ; Chen Wang ; Laura M. K. Dassama ; Bo Zhang ; Yisong GuoLauren J. Rajakovich ; J. Martin Bollinger Jr. ; Carsten Krebs ; Wilfred A. van der Donk
• 刊名：Journal of the American Chemical Society
• 出版年：2017
• 出版时间：February 8, 2017
• 年：2017
• 卷：139
• 期：5
• 页码：2045-2052
• 全文大小：466K
• ISSN：1520-5126

文摘

Activation of O–H bonds by inorganic metal-oxo complexes has been documented, but no cognate enzymatic process is known. Our mechanistic analysis of 2-hydroxyethylphosphonate dioxygenase (HEPD), which cleaves the C1–C2 bond of its substrate to afford hydroxymethylphosphonate on the biosynthetic pathway to the commercial herbicide phosphinothricin, uncovered an example of such an O–H-bond-cleavage event. Stopped-flow UV–visible absorption and freeze-quench Mössbauer experiments identified a transient iron(IV)-oxo (ferryl) complex. Maximal accumulation of the intermediate required both the presence of deuterium in the substrate and, importantly, the use of ²H₂O as solvent. The ferryl complex forms and decays rapidly enough to be on the catalytic pathway. To account for these unanticipated results, a new mechanism that involves activation of an O–H bond by the ferryl complex is proposed. This mechanism accommodates all available data on the HEPD reaction.