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O–H Activation by an Unexpected Ferryl Intermediate during Catalysis by 2-Hydroxyethylphosphonate Dioxygenase
- Peck, Spencer
C., Wang, Chen, Dassama, Laura M. K., Zhang, Bo, Guo, Yisong, Rajakovich, Lauren J., Bollinger, J. Martin, Krebs, Carsten, van der Donk, Wilfred A.
- Journal of the American Chemical Society 2017 v.139 no.5 pp. 2045-2052
- absorption, biochemical pathways, catalytic activity, chemical bonding, deuterium, deuterium oxide, glufosinate, iron, solvents
- 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.