Nickel-promoted reductive C-S bond cleavage: A model for the first step in the reaction promoted by methyl coenzyme M reductase

Journal Article · Wed Apr 28 00:00:00 EDT 1993 · Inorganic Chemistry; (United States)

OSTI ID:6043895

Cha, Mikyung; Shoner, S C; Kovacs, J A ^[1]

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1. Univ. of Washington, Seattle (United States)

Sulfur-ligated Ni complexes are of interest as active-site models of the Ni-containing enzymes hydrogenase (H[sub 2]-ase), methyl coenzyme M reductase (Me-CoM reductase), and Co-dehydrogenase (CODH). Me-CoM reductase catalyzes the last step in the reaction sequence which converts CO[sub 2] to CH[sub 4] in methanogenic bacteria. This step involves the cleavage of the methyl thioether C-S bond of the substrate methyl coenzyme M (Me-S-CoM). Ni(I) is believed to be the active species responsible for promoting this reaction. However, it has been difficult to probe the mechanism by which this occurs, since Me-CoM reductase rapidly loses activity upon breakage of whole cells during purification. Only one Ni complex, Ni[sup II](dioxo[16]aneN[sub 5]), has been shown to induce stoichiometric methane formation from Me-S-CoM; however, the mechanism proposed to explain this reaction is difficult to understand, and involves a Ni(II/III), as opposed to a Ni(I/II), redox couple. Other nickel complexes have been shown to desulfurize thioethers in the presence of reducing agents (e.g., LiAlH[sub 4]); however, the reactive Ni species have not been characterized. As part of a systematic study aimed at determining the influence of the local Ni coordination environment on reactivity, the authors have synthesized a series of structurally related sulfur-ligated Ni(II) complexes, including Ni[sup II]L[sub S5] (1). Since redox changes (Ni(III) [yields] Ni(II) and/or Ni(II) [yields] Ni(I)) appear to play an important role in the mechanisms of the enzymes mentioned above, the authors have also examined the redox chemistry of these molecules. Herein, they report a Ni-promoted reductive C-S bond cleavage reaction that represents a plausible chemical model for the first step in the reaction promoted by Ni in Me-CoM reductase. 30 refs., 4 figs.

• OSTI ID: 6043895
• Journal Information: Inorganic Chemistry; (United States), Vol. 32:9; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
09 BIOMASS FUELS
NICKEL COMPLEXES
ELECTROCHEMISTRY
SULFIDES
CATALYTIC EFFECTS
CHEMICAL BONDS
CHEMICAL PREPARATION
CLEAVAGE
ELECTROLYTIC CELLS
ENZYMES
METHANE
METHANOGENIC BACTERIA
ORGANIC SULFUR COMPOUNDS
REACTIVITY
VOLTAMETRY
ALKANES
BACTERIA
CHALCOGENIDES
CHEMISTRY
COMPLEXES
HYDROCARBONS
MICROORGANISMS
MICROSTRUCTURE
ORGANIC COMPOUNDS
PROTEINS
SULFUR COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
400400* - Electrochemistry
550200 - Biochemistry
090900 - Biomass Fuels- Processing- (1990-)