Enzymatic Methane Hydroxylation: sMMO and pMMO
59
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
O
HC
O
O
CH
3
H
O
H
H
O
C
H
O
N
H
N
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
O
HC
O
O
H
CH
3
O
H
H
O
C
H
O
N
H
N
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
O
HC
O
O
CH
3
O
H
H
O
C
H
O
N
H
N
H
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
H
O
O
CH
3
O
C
H
O
N
H
N
H
O
O
HC
H
Hydroxo intermediate
MMOH
Q + CH
4
MMOH
red + CH
4 + O
2
0.0
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
O
HC
O
O
O
H
H
O
C
H
O
N
H
N
CH
4
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
O
CH
O
O
O
H
H
O
C
H
O
N
H
N
Fe
O
C
H
O
Fe
O
O
CH
N
NH
O
O CH
O
H
H
O
C
H
O
N
H
N
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
O
HC
O
O
O
H
H
O
C
H
O
N
H
N
Fe
O
C
H
O
Fe
O
O
CH
N
NH
O
O
CH
O
O
O
H
H
O
CH
O
N
HN
Methane complex
End-on peroxo complex
+ CH
4
Side-on peroxo complex
+ CH
4
Fe
O
C
H
O
Fe
O
O
HC
N
NH
O
H
O
O
CH
3
O
C
H
O
N
H
N
H
O
O CH
H
MMOH
T
Methanol complex
TS1
TS2
Fig. 8
Potential energy diagram for dioxygen activation and methane hydroxylation by MMOH
Q in the broken-symmetry singlet state at B3LYP calculations.
Energy relative to MMOH
red
+ O
2
+ CH
4 are in kcal/mol. MMOH
Q has coordinatively unsaturated diiron active site corresponding to that in Fig. 4c. Reproduced
from Ref. [52] by permission of Wiley Ltd.