posted on 2024-01-03, 09:08authored byZhiwei Deng, Hao Su, Xiaodong Hou, Huibin Xu, Zhenbo Yuan, Xiang Sheng, Yijian Rao
An atypical nonheme iron-dependent dioxygenase BTG13
with a rare
iron coordination of four histidine residues and a carboxylated-lysine
(Kcx) was recently reported to catalyze the C4a–C10 bond cleavage of anthraquinone. However, the reaction mechanism
of BTG13 remains elusive. Herein, the detailed mechanism of BTG13
is studied using molecular dynamics simulations and density functional
theory calculations. The comprehensive mechanistic study shows that
the most favorable pathway for the C–C bond cleavage of anthraquinone
involves two unusual steps: (1) a hydrogen atom abstraction (HAA)
from an sp3-hybridized carbon of the substrate by FeIII–O2•– and (2)
an oxygen rebound to the substrate radical via homolytic O–O
bond cleavage, which activates FeIII–OOH to form
FeIVO species. Furthermore, our results reveal
that Kcx could increase the electron-donating ability of the ferrous
iron, thereby boosting the activation of dioxygen to form FeIII–O2•– species and facilitating
the following HAA and O–O bond cleavage processes. This study
advances the current knowledge of reactions catalyzed by iron-dependent
oxygenases.