title: A tale of two methane monooxygenases.
abstract: Methane monooxygenase (MMO) enzymes activate O2for oxidation of methane. Two distinct MMOs exist in nature, a soluble form that uses a diiron active site (sMMO) and a membrane-bound form with a catalytic copper center (pMMO). Understanding the reaction mechanisms of these enzymes is of fundamental importance to biologists and chemists, and is also relevant to the development of new biocatalysts. The sMMO catalytic cycle has been elucidated in detail, including O2activation intermediates and the nature of the methane-oxidizing species. By contrast, many aspects of pMMO catalysis remain unclear, most notably the nuclearity and molecular details of the copper active site. Here, we review the current state of knowledge for both enzymes, and consider pMMO O2activation intermediates suggested by computational and synthetic studies in the context of existing biochemical data. Further work is needed on all fronts, with the ultimate goal of understanding how these two remarkable enzymes catalyze a reaction not readily achieved by any other metalloenzyme or biomimetic compound.
authors.affiliation: Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, IL, 60208, USA.
authors.forename: Matthew O
authors.initials: MO
authors.lastname: Ross
authors.affiliation: Departments of Molecular Biosciences and of Chemistry, Northwestern University, Evanston, IL, 60208, USA. amyr@northwestern.edu.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Rosenzweig
mesh_terms: D020134:Catalytic Domain; D006801:Humans; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism*; D012995:Solubility
chemical_list: D010105:Oxygenases; C021555:methane monooxygenase
keywords: Copper; Diiron; Dioxygen activation; Methane monooxygenase; Methanotroph