Metil coenzima M redutase (MCR) e o fator 430 (F430)

Nakagaki, Shirley; Friedermann, Geraldo R.; Caiut, José Maurício A.

doi:10.1590/s0100-40422006000500022

Cited by 5 publications

(1 citation statement)

References 26 publications

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“…This opened up the way to properly study the different states of MCR using biophysical methods. Several recent reviews give in-depth overviews of these investigations. ,− Although there is a good understanding of the properties of the different states that can be detected in MCR, there is limited information available on the actual reaction mechanism.…”

Section: Introductionmentioning

confidence: 99%

A New Mechanism for Methane Production from Methyl-Coenzyme M Reductase As Derived from Density Functional Calculations

Duin

McKee

2008

J. Phys. Chem. B

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We propose a new DFT-based mechanism for methane production using the full F430 cofactor of MCR (methyl-coenzyme M reductase) along with a coordinated O=CH2CH2C(H)NH2C(H)O (surrogate for glutamine) as a model of the active site for conversion of CH3SCoM(-) (CH3SCH2CH2SO3(-)) + HSCoB to methane plus the corresponding heterodisulfide. The cycle begins with the protonation of F430, either on Ni or on the C-ring nitrogen of the tetrapyrrole ring, both of which are nearly equally favorable. The C-ring protonated form is predicted to oxidatively add CH3SCoM(-) to give a 4-coordinate Ni center where the Ni moves out of the plane of the four ring nitrogens. The movement of Ni (and the attached CH3 and SCH2CH2SO3(2-) ligands) toward the SCoB(-) (deprotonated HSCoB) cofactor allows a 2c-3e interaction to form between the two sulfur atoms. The release of the heterodisulfide yields a Ni(III) center with a methyl group attached. The concerted elimination of methane, where the methyl group coordinated to Ni abstracts the proton from the C-ring nitrogen, has a very small calculated activation barrier (5.4 kcal/mol). The NPA charge on Ni for the various reaction steps indicates that the oxidation state changes occur largely on the attached ligands.

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