Conversion of methane to methanol at the mononuclear and dinuclear copper sites of particulate methane monooxygenase (pMMO)

A DFT and QM/MM study

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Abstract

Methane hydroxylation at the mononuclear and dinuclear copper sites of pMMO is discussed using quantum mechanical and QM/MM calculations. Possible mechanisms are proposed with respect to the formation of reactive copper-oxo and how they activate methane. Dioxygen is incorporated into the CuI species to give a CuII-superoxo species, followed by an H-atom transfer from a tyrosine residue near the monocopper active site. A resultant CuII-hydroperoxo species is next transformed into a Cu III-oxo species and a water molecule by the abstraction of an H-atom from another tyrosine residue. This process is accessible in energy under physiological conditions. Dioxygen is also incorporated into the dicopper site to form a (μ-η22-peroxo)dicopper species, which is then transformed into a bis(μ-oxo)dicopper species. The formation of this species is more favorable in energy than that of the monocopper-oxo species. The reactivity of the CuIII-oxo species is sufficient for the conversion of methane to methanol if it is formed in the protein environment. Since the σ* orbital localized in the Cu-O bond region is singly occupied in the triplet state, this orbital plays a role in the homolytic cleavage of a C-H bond of methane. The reactivity of the bis(μ-oxo)dicopper species is also sufficient for the conversion of methane to methanol. The mixed-valent bis(μ-oxo)CuIICuIII species is reactive to methane because the amplitude of the σ* singly occupied MO localized on the bridging oxo moieties plays an essential role in C-H activation.

Original languageEnglish
Pages (from-to)9873-9881
Number of pages9
JournalJournal of the American Chemical Society
Volume128
Issue number30
DOIs
Publication statusPublished - Aug 2 2006

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methane monooxygenase
Methane
Discrete Fourier transforms
Methanol
Copper
Tyrosine
Oxygen
Atoms
Hydroxylation
Catalytic Domain
Chemical activation

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

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title = "Conversion of methane to methanol at the mononuclear and dinuclear copper sites of particulate methane monooxygenase (pMMO): A DFT and QM/MM study",
abstract = "Methane hydroxylation at the mononuclear and dinuclear copper sites of pMMO is discussed using quantum mechanical and QM/MM calculations. Possible mechanisms are proposed with respect to the formation of reactive copper-oxo and how they activate methane. Dioxygen is incorporated into the CuI species to give a CuII-superoxo species, followed by an H-atom transfer from a tyrosine residue near the monocopper active site. A resultant CuII-hydroperoxo species is next transformed into a Cu III-oxo species and a water molecule by the abstraction of an H-atom from another tyrosine residue. This process is accessible in energy under physiological conditions. Dioxygen is also incorporated into the dicopper site to form a (μ-η2:η2-peroxo)dicopper species, which is then transformed into a bis(μ-oxo)dicopper species. The formation of this species is more favorable in energy than that of the monocopper-oxo species. The reactivity of the CuIII-oxo species is sufficient for the conversion of methane to methanol if it is formed in the protein environment. Since the σ* orbital localized in the Cu-O bond region is singly occupied in the triplet state, this orbital plays a role in the homolytic cleavage of a C-H bond of methane. The reactivity of the bis(μ-oxo)dicopper species is also sufficient for the conversion of methane to methanol. The mixed-valent bis(μ-oxo)CuIICuIII species is reactive to methane because the amplitude of the σ* singly occupied MO localized on the bridging oxo moieties plays an essential role in C-H activation.",
author = "Kazunari Yoshizawa and Yoshihito Shiota",
year = "2006",
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TY - JOUR

T1 - Conversion of methane to methanol at the mononuclear and dinuclear copper sites of particulate methane monooxygenase (pMMO)

T2 - A DFT and QM/MM study

AU - Yoshizawa, Kazunari

AU - Shiota, Yoshihito

PY - 2006/8/2

Y1 - 2006/8/2

N2 - Methane hydroxylation at the mononuclear and dinuclear copper sites of pMMO is discussed using quantum mechanical and QM/MM calculations. Possible mechanisms are proposed with respect to the formation of reactive copper-oxo and how they activate methane. Dioxygen is incorporated into the CuI species to give a CuII-superoxo species, followed by an H-atom transfer from a tyrosine residue near the monocopper active site. A resultant CuII-hydroperoxo species is next transformed into a Cu III-oxo species and a water molecule by the abstraction of an H-atom from another tyrosine residue. This process is accessible in energy under physiological conditions. Dioxygen is also incorporated into the dicopper site to form a (μ-η2:η2-peroxo)dicopper species, which is then transformed into a bis(μ-oxo)dicopper species. The formation of this species is more favorable in energy than that of the monocopper-oxo species. The reactivity of the CuIII-oxo species is sufficient for the conversion of methane to methanol if it is formed in the protein environment. Since the σ* orbital localized in the Cu-O bond region is singly occupied in the triplet state, this orbital plays a role in the homolytic cleavage of a C-H bond of methane. The reactivity of the bis(μ-oxo)dicopper species is also sufficient for the conversion of methane to methanol. The mixed-valent bis(μ-oxo)CuIICuIII species is reactive to methane because the amplitude of the σ* singly occupied MO localized on the bridging oxo moieties plays an essential role in C-H activation.

AB - Methane hydroxylation at the mononuclear and dinuclear copper sites of pMMO is discussed using quantum mechanical and QM/MM calculations. Possible mechanisms are proposed with respect to the formation of reactive copper-oxo and how they activate methane. Dioxygen is incorporated into the CuI species to give a CuII-superoxo species, followed by an H-atom transfer from a tyrosine residue near the monocopper active site. A resultant CuII-hydroperoxo species is next transformed into a Cu III-oxo species and a water molecule by the abstraction of an H-atom from another tyrosine residue. This process is accessible in energy under physiological conditions. Dioxygen is also incorporated into the dicopper site to form a (μ-η2:η2-peroxo)dicopper species, which is then transformed into a bis(μ-oxo)dicopper species. The formation of this species is more favorable in energy than that of the monocopper-oxo species. The reactivity of the CuIII-oxo species is sufficient for the conversion of methane to methanol if it is formed in the protein environment. Since the σ* orbital localized in the Cu-O bond region is singly occupied in the triplet state, this orbital plays a role in the homolytic cleavage of a C-H bond of methane. The reactivity of the bis(μ-oxo)dicopper species is also sufficient for the conversion of methane to methanol. The mixed-valent bis(μ-oxo)CuIICuIII species is reactive to methane because the amplitude of the σ* singly occupied MO localized on the bridging oxo moieties plays an essential role in C-H activation.

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