Enzymatic Methane Hydroxylation:
sMMO and pMMO
Takashi Yumura, Takehiro Ohta, and Kazunari Yoshizawa
Abstract Catalytic function of methane monooxygenase (MMO) for the conversion
of methane to methanol at ambient pressure and temperature has fascinated many
researchers. This chapter will review quantum chemical approaches, especially by
means of density functional theory (DFT) calculations, to elucidate mechanisms for
the methane hydroxylation by active sites of MMO (soluble and particulate MMOs)
with a focus on how a methane C–H bond is activated. Because of the uncertainty
in the coordination environment of transition metal cations in the active site that
has a direct reactivity toward substrate methane, different computational models in
various spin states have been used. Reflecting from these differences, a variety of
mechanisms for the methane hydroxylation on MMO has been proposed: radicalrelated mechanisms (radical-rebound and nonsynchronous concerted mechanisms)
and nonradical mechanism. These proposed mechanisms will be compared. In addition, key factors in determining the reactivity of MMO will be discussed on the basis
of molecular orbital theory applied to transition-metal containing active sites.
Keywords Density functional theory calculations · Activation of a methane C–H
bond · Spin states · Reaction mechanism · Coordination environment
T. Yumura (B)
Faculty of Materials Science and Engineering, Graduate School of Science and Technology,
Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
e-mail: yumura@kit.ac.jp
T. Ohta
Department of Applied Chemistry, Faculty of Engineering, Sanyo-Onoda City University,
Yamaguchi 756-0884, Japan
K. Yoshizawa
Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku,
Fukuoka 819-0395, Japan
© Springer Nature Singapore Pte Ltd. 2020
K. Yoshizawa (ed.), Direct Hydroxylation of Methane,
https://doi.org/10.1007/978-981-15-6986-9_3
45
sMMO and pMMO
Takashi Yumura, Takehiro Ohta, and Kazunari Yoshizawa
Abstract Catalytic function of methane monooxygenase (MMO) for the conversion
of methane to methanol at ambient pressure and temperature has fascinated many
researchers. This chapter will review quantum chemical approaches, especially by
means of density functional theory (DFT) calculations, to elucidate mechanisms for
the methane hydroxylation by active sites of MMO (soluble and particulate MMOs)
with a focus on how a methane C–H bond is activated. Because of the uncertainty
in the coordination environment of transition metal cations in the active site that
has a direct reactivity toward substrate methane, different computational models in
various spin states have been used. Reflecting from these differences, a variety of
mechanisms for the methane hydroxylation on MMO has been proposed: radicalrelated mechanisms (radical-rebound and nonsynchronous concerted mechanisms)
and nonradical mechanism. These proposed mechanisms will be compared. In addition, key factors in determining the reactivity of MMO will be discussed on the basis
of molecular orbital theory applied to transition-metal containing active sites.
Keywords Density functional theory calculations · Activation of a methane C–H
bond · Spin states · Reaction mechanism · Coordination environment
T. Yumura (B)
Faculty of Materials Science and Engineering, Graduate School of Science and Technology,
Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
e-mail: yumura@kit.ac.jp
T. Ohta
Department of Applied Chemistry, Faculty of Engineering, Sanyo-Onoda City University,
Yamaguchi 756-0884, Japan
K. Yoshizawa
Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku,
Fukuoka 819-0395, Japan
© Springer Nature Singapore Pte Ltd. 2020
K. Yoshizawa (ed.), Direct Hydroxylation of Methane,
https://doi.org/10.1007/978-981-15-6986-9_3
45