68
T. Yumura et al.
0.0(0.7)
2.8
(3.4)
18.9
(19.7)
9.1
(9.8)
OXO + CH 4
19.7
(19.8)
1
2
TS1
TS2
3
Tyr-O
Cu II
Cu III
H
O
O
Tyr-O
Cu I
Cu II
HO
H
O
CH 3
TS1
TS2
2
3
1.224
1.287
2.452
OXO
2.262
2.514
1
.9
5
5
2.539
1.915
2 .2 2 3
2.281
Tyr-OH
Cu II
Cu II
HO
O
CH 3
4
2.939
2.940
2.9 07
3.5 31
2.787
2 .4 6 7
Tyr-O
Cu II
Cu II
H
O
O
H
CH 3
Tyr-O
Cu II
Cu III
H
O
O
H
H 3 C
Tyr-O
Cu II
Cu II
H
O
HO CH 3
Fig. 16 Energy diagram for the conversion of methane to methanol by the (μ-O) (μOH)Cu(II)Cu(III) species of pMMO in the triplet (singlet) state at the B3LYP level. Units in
kcal/mol. Reprinted with the permission from Ref. [116]. Copyright 2013 American Chemical
Society
(μ-O)(μ-OH)Cu(II)Cu(III) active site, being higher than that in the recombination
step (10.6 kcal/mol). DFT calculations suggested that the Tyr374 residue plays an
important role in enhancing the reactivity of the bis(μ-oxo) dicopper active site due
to an H-atom transfer from the residue. The above DFT findings on the methane
hydroxylation on pMMO are also important to give a useful hint to understand