Open AccessO–H Activation by an Unexpected Ferryl Intermediate during Catalysis by 2-Hydroxyethylphosphonate Dioxygenase
Author(s) -
Spencer C. Peck,
Chen Wang,
Laura M. K. Dassama,
Bo Zhang,
Yisong Guo,
Lauren J. Rajakovich,
J. Martin Bollinger,
Carsten Krebs,
Wilfred A. van der Donk
Publication year - 2017
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.6b12147
Subject(s) - chemistry , dioxygenase , bond cleavage , catalysis , photochemistry , substrate (aquarium) , catalytic cycle , stereochemistry , solvent , cleavage (geology) , reaction mechanism , enzyme , organic chemistry , oceanography , geotechnical engineering , fracture (geology) , engineering , geology
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 2 H 2 O 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.