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Formation of a Nickel−Methyl Species in Methyl-Coenzyme M Reductase, an Enzyme Catalyzing Methane Formation

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journal contribution
posted on 12.09.2007, 00:00 by Na Yang, Markus Reiher, Mi Wang, Jeffrey Harmer, Evert C. Duin
An organometallic methyl−nickel species was detected in the enzyme methyl-coenzyme M reductase (MCR). This is the key enzyme in microbial methane production and is probably also involved in anaerobic methane oxidation. Incubation of MCR with 13C-bromomethane results in the formation of an electron paramagnetic resonance (EPR) active nickel−methyl species in the active site of this enzyme. High-resolution pulse electron nuclear double resonance and hyperfine sublevel correlation investigations showed the presence of 13C hyperfine couplings of 18−44 MHz that are associated with the nickel-based EPR signal. The large 13C hyperfine interaction shows unambiguously that the methyl group from bromomethane is directly coordinated to the nickel ion. The EPR structure and parameters are fully supported by density functional theory calculations.