C(sp<sup>3</sup>)−H Hydroxylation in Diiron β‐Hydroxylase CmlA Transpires by Amine‐Assisted O<sub>2</sub> Activation Avoiding Fe<sup>IV</sup><sub>2</sub>O<sub>2</sub> Species
Jiarui Lu, Wenzhen Lai, Hui Chen
Abstract
Abstract Through QM/MM modeling, we discovered that C(sp 3 )−H β ‐ hydroxylation in the diiron hydroxylase CmlA transpires by traceless amine‐assisted O 2 activation. Different from the canonical diiron hydroxylase sMMO, this aliphatic‐amine‐assisted O 2 activation avoids generating the high‐valent diferryl Fe IV 2 O 2 species, but alternatively renders a diferric Fe III 2 O species as the reactive oxidant. From this unprecedented O 2 activation mode, the derived C(sp 3 )−H hydroxylation mechanism in CmlA also differs drastically from the toluene aromatic C(sp 2 )−H hydroxylation in the diiron hydroxylase T4MO. This substrate‐modulated O 2 activation in CmlA has rich mechanistic implications for other diiron hydroxylases with an amine group adjacent to the C−H bond under hydroxylation in substrates, such as hDOHH. Furthermore, the adapted coordination environment of the diiron cofactor upon O 2 binding in CmlA opens up more structural and mechanistic possibilities for O 2 activation in non‐heme diiron enzymes.