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Methane monooxygenase belongs to the class of oxidoreductase enzymes (EC 1.14.13.25). There are two forms of MMO: the well-studied soluble form (sMMO) and the particulate form (pMMO). [2] The active site in sMMO contains a di-iron center bridged by an oxygen atom (Fe-O-Fe), whereas the active site in pMMO utilizes copper.
Structure of pMMO. Rosenzweig determined the molecular structures of Nature's main methane oxidation catalysts. Methane monooxygenases are metalloenzymes found in the family of methanotrophic bacteria. These enzymes belong in the oxidoreductase class. They activate carbon-hydrogen bonds to selectively install oxygen onto their substrate.
Cells containing pMMO have demonstrated higher growth capabilities and higher affinity for methane than sMMO containing cells. [7] It is suspected that copper ions may play a key role in both pMMO regulation and the enzyme catalysis, thus limiting pMMO cells to more copper-rich environments than sMMO producing cells. [30]
Methanobactin (mb) is a class of copper-binding and reducing chromophoric peptides initially identified in the methanotroph Methylococcus capsulatus Bath - and later in Methylosinus trichosporium OB3b - during the isolation of the membrane-associated or particulate methane monooxygenase (pMMO). [1]
The overall reactions are: CH 4 + 4 NO 3 − → CO 2 + 4 NO 2 − + 2 H 2 O 3 CH 4 + 8 NO 2 − + 8 H + → 3 CO 2 + 4 N 2 + 10 H 2 O. ANME-2d is shown to be responsible nitrate-driven AOM. [5] The ANME-2d, named Methanoperedens nitroreducens, is able to perform nitrate-driven AOM without a partner organism via reverse methanogenesis with nitrate as the terminal electron acceptor, using genes ...
Of the two half reactions, the oxidation step is the most demanding because it requires the coupling of 4 electron and proton transfers and the formation of an oxygen-oxygen bond. This process occurs naturally in plants photosystem II to provide protons and electrons for the photosynthesis process and release oxygen to the atmosphere, [ 1 ] as ...
Some organisms can oxidize methane, functionally reversing the process of methanogenesis, also referred to as the anaerobic oxidation of methane (AOM). Organisms performing AOM have been found in multiple marine and freshwater environments including methane seeps, hydrothermal vents, coastal sediments and sulfate-methane transition zones. [8]
Most methane is stranded, i.e. not located near metropolitan areas. Consequently, it is flared (converted to carbon dioxide). One challenge is that methanol is more easily oxidized than is methane. [3] Catalytic oxidation with oxygen or air is a major application of green chemistry. There are however many oxidations that cannot be achieved so ...