Subhendu Roy and Johannes Kästner*
Institute for Theoretical Chemistry University of Stuttgart Pfaffenwaldring 55, 70569 Stuttgart (Germany)
Angew. Chem. Int. Ed. 2015, 54, 1 – 6
Abstract: Salicylate 1,2-dioxygenase (SDO) is the first enzyme
to be discovered to catalyze the oxidative cleavage of a mono-
hydroxylated aromatic compound, namely salicylate, instead
of the well-known electron-rich substrates. We have investi-
gated the mechanism of dioxygen activation in SDO by QM/
MM calculations. Our study reveals that the non-heme FeII
center in SDO activates salicylate and O2 synergistically
through a strong covalent interaction to facilitate the reductive
cleavage of O2. A covalent salicylate–FeII–O2 complex is the
reactive oxygen species in this case, and its electronic structure
is best described as being between the two limiting cases,
FeII-O2 and FeII-O2.-, with partial electron transfer from the
activated salicylate to O2 via the Fe center. Thus SDO employs
a synergistic strategy of substrate and oxygen activation to
carry out the catalytic reaction, which is unprecedented in the
family of iron dioxygenases. Moreover, O2 activation in SDO
happens without the assistance of a proton source. Our study
essentially shows a new mechanistic possibility for O2 activation.
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