scholarly journals Particulate methane monooxygenase contains only mononuclear copper centers

Science ◽  
2019 ◽  
Vol 364 (6440) ◽  
pp. 566-570 ◽  
Author(s):  
Matthew O. Ross ◽  
Fraser MacMillan ◽  
Jingzhou Wang ◽  
Alex Nisthal ◽  
Thomas J. Lawton ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Methane Oxidation ◽  
Active Site ◽  
Methane Monooxygenase ◽  
Spectroscopic Characterization ◽  
Metabolic Enzyme ◽  
Particulate Methane Monooxygenase ◽  
Paramagnetic Resonance ◽  
Membrane Bound ◽  
Electron Paramagnetic

Bacteria that oxidize methane to methanol are central to mitigating emissions of methane, a potent greenhouse gas. The nature of the copper active site in the primary metabolic enzyme of these bacteria, particulate methane monooxygenase (pMMO), has been controversial owing to seemingly contradictory biochemical, spectroscopic, and crystallographic results. We present biochemical and electron paramagnetic resonance spectroscopic characterization most consistent with two monocopper sites within pMMO: one in the soluble PmoB subunit at the previously assigned active site (CuB) and one ~2 nanometers away in the membrane-bound PmoC subunit (CuC). On the basis of these results, we propose that a monocopper site is able to catalyze methane oxidation in pMMO.

scholarly journals CH4-to-CH3OH on Mononuclear Cu(II) Sites Supported on Al2O3: Structure of Active Sites from Electron Paramagnetic Resonance

2021 ◽  
Author(s):  
Jordan Meyet ◽  
Anton Ashuiev ◽  
Gina Noh ◽  
Mark Newton ◽  
Daniel Klose ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Organometallic Chemistry ◽  
Active Sites ◽  
Spectroscopic Characterization ◽  
Paramagnetic Resonance ◽  
Transition Alumina ◽  
Selective Conversion ◽  
Conversion Of Methane ◽  
Electron Paramagnetic ◽  
Alumina Supports

The selective conversion of methane to methanol remains one of the holy grails of chemistry, where Cu-exchanged zeolites have been shown to selectively convert methane to methanol under stepwise conditions. Over the years, several active sites have been proposed, ranging from mono-, di- to trimeric Cu(II). Herein, we report the formation of well-dispersed monomeric Cu(II) species supported on alumina using surface organometallic chemistry and their reactivity towards the selective and stepwise conversion of methane to methanol. Extensive studies using various transition alumina supports combined with spectroscopic characterization, in particular electron paramagnetic resonance (EPR), show that the active sites are associated with specific facets, which are typically found in gamma- and eta-alumina phase, and that their EPR signature can be attributed to species having a tri-coordinated [(Al<sub>2</sub>O)Cu<sup>II</sup>O(OH)]<sup>-</sup>,T-shape geometry. Overall, the selective conversion of methane to methanol, a two-electron process, involve two of these isolated monomeric Cu(II) sites that play in concert.

scholarly journals The nature of the phosphate inhibitor complex of sulphite oxidase from electron-paramagnetic-resonance studies using oxygen-17

1980 ◽  
Vol 191 (1) ◽  
pp. 285-288 ◽  
Author(s):  
S Gutteridge ◽  
M T Lamy ◽  
R C Bray
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Active Site ◽  
Detectable Effect ◽  
Paramagnetic Resonance ◽  
Enzyme Reactions ◽  
Inhibitor Complex ◽  
Sulphite Oxidase ◽  
Oxygen Ligand ◽  
Normal Water ◽  
Electron Paramagnetic

Studies of the effect of substitution with 17O on the e.p.r. spectra at 9 and 35 GHz of Mo(V) in the phosphate complex of sulphite oxidase are reported. Substitution of 17O-enriched water for normal water, for samples of the enzymes reduced by sulphite in the presence of normal phosphate, produced no detectable effect on the e.p.r. signal. If phosphate substituted with 17O was used, coupling due to 17O, producing large anisotropic splittings in the spectrum, was clearly detectable. It is concluded that phosphate is co-ordinated directly to molybdenum in the active site of the enzyme, in an equatorial type of ligand position. An oxygen ligand must be displaced from the molybdenum in the process of binding the phosphate. Implications concerning the mechanism of the enzyme reactions are discussed.

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