Catalytic properties of the heterodisulfide reductase involved in the final step of methanogenesis

Hedderich, Reiner; Berkessel, Albrecht; Thauer, Rudolf K.

doi:10.1016/0014-5793(89)81062-2

Cited by 50 publications

(25 citation statements)

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“…The two electrons required for the reduction derive from the sulfur atoms of CH3-S-CoM and HS-HTP (7-mercaptoheptanoylthreonine phosphate) (9), yielding the heterodisulfide CoM-S-S-HTP. In the pathway for methanogenesis from acetate, the mixed disulfide is reduced to the corresponding sulfhydryl forms of the cofactors with electrons originating from oxidation of the carbonyl group of acetyl-CoA (21,47). The thermodynamics of both heterodisulfide formation and reduction (reactions 5 and 6) suggests a potential for electron transport coupled to ATP synthesis.…”

Section: Introductionmentioning

confidence: 99%

Methane from acetate

1992

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INTRODUCTIONAnaerobic microorganisms play a major role in the global carbon cycle by remineralizing the large quantities of organic matter which enter anoxic marine and freshwater environments. Methane and CO2 are the end products of anaerobic decomposition, which occurs in a diversity of habitats, such as the rumens of ruminant animals, the lower intestinal tracts of humans, sewage digesters, landfills, rice paddies, and the sediments of freshwater lakes and rivers. Most of the methane released is oxidized to CO2 by the strictly aerobic methanotrophs; however, a significant proportion escapes into the upper atmosphere where methane has a major role in the greenhouse effect.The methanogenic decomposition of organic matter requires microbial consortia composed of at least three interacting metabolic groups of anaerobes. The fermentative bacteria degrade polymers to H2, CO2, formate, acetate, and higher volatile carboxylic acids. The acetogenic bacteria then oxidize the higher acids to acetate and either H2 or formate. The strictly anaerobic methane-producing microorganisms are the final group in the consortia and utilize H2, formate, and acetate as substrates for growth. Methane producers represent the largest and most diverse group within the Archaea domain (57). The reader is referred to reviews that describe general aspects of the methanogenic members of the Archaea domain (32, 56).About two-thirds of the methane produced in nature originates from the methyl group of acetate, and about one-third originates from the reduction of CO2 with electrons derived from the oxidation of H2 or formate. Two independent pathways exist for the conversion of acetate and reduction of CO2. The pathway of CO2 reduction to methane has been studied extensively over the past 20 years and is the subject of several reviews (9,34,51,55); however, a fundamental understanding of methanogenesis from acetate has emerged only recently.Most acetate-utilizing anaerobes from the Bacteria domain cleave acetyl coenzyme A (acetyl-CoA) and oxidize the methyl and carbonyl groups completely to CO2, reducing a variety of electron acceptors (52). In contrast, the methanogenic members of the Archaea domain carry out a fermentation of acetate in which the molecule is cleaved and the methyl group is reduced to methane with electrons derived from oxidation of the carbonyl group to CO2 (reaction 1).

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Section: Introductionmentioning

confidence: 99%

Methane from acetate

1992

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“…Cell extracts of M. thermoautotrophicurn were shown to catalyze the reduction of CoM-S-S-HTP with H, (H,:heterodisulfide oxidoreductase activity; Hedderich and Thauer, 1988) and with reduced viologen dyes as artificial electron donors (heterodisulfide-reductase activity; Hedderich et al, 1989). Both activities were associated with the soluble cell fraction.…”

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confidence: 99%

H₂: heterodisulfide oxidoreductase complex from Methanobacterium thermoautotrophicum

Setzke

Hedderich

Heiden

et al. 1994

European Journal of Biochemistry

100

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The reduction of the heterodisulfide (CoM-S-S-HTP) of coenzyme M (H-S-CoM) and N-7-mercaptoheptanoylthreonine phosphate (H-S-HTP) with H, is an energy-conserving step in most methanogenic Archaea. In this study, we show that in Methanobacterium thermoautotrophicum (strain Marburg) this reaction is catalyzed by a stable H, :heterodisulfide oxidoreductase complex of F4,,,-non-reducing hydrogenase and heterodisulfide reductase. This complex, which was loosely associated with the cytoplasmic membrane, was purified 17-fold with 80% yield to apparent homogeneity. The purified complex was composed of six different subunits of apparent molecular masses 80, 51, 41, 36, 21 and 17 kDa, and 1 mol complex, with apparent molecular mass 250 kDa, contained approximately 0.6 mol nickel, 0.9 mol FAD, 26 mol non-heme iron and 22 mol acid-labile sulfur. In 25 mM Chaps, the complex partially dissociated into two subcomplexes. The first subcomplex was was composed of the 51-, 41-and 17-kDa subunits; 1 mol trimer contained 0.7 mol nickel, 10 mol non-heme iron and 9 mol acid-labile sulfur and exhibited F,,,-non-reducing hydrogenase activity. The other subcomplex was composed of the 80-, 36-and 21-kDa subunits; 1 mol trimer contained 0.8 mol FAD, 22 mol non-heme iron and 15 mol acid-labile sulfur and exhibited heterodisulfide-reductase activity. The stimulatory effects of potassium phosphate, a membrane component, uracil derivatives and coenzyme F,,, on the H, :heterodisulfide-oxidoreductase activity of the purified complex are described.

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“…Methanobacterium thermoautotrophicum a Hz-dependent and a benzyl viologen-dependent heterodisulfide reductase was found in the cytoplasmic fraction [10,12] whereas in the meth~ogenic strain G61 a F420H2 -dependent 1131 and a Hz-dependent (unpublished results) CoM-S-S-HTP reductase were membrane-bound. It remains now to be shown how the electron transfer from Ht to the heterodisulfide leads to the generation of an electrochemical transmembrane proton gradient.…”

Section: Discussionmentioning

confidence: 99%

ATP synthesis coupled to electron transfer from H₂ to the heterodisulfide of 2‐mercaptoethanesulfonate and 7‐mercaptoheptanoylthreonine phosphate in vesicle preparations of the methanogenic bacterium strain Gö1

et al. 1990

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Crude vesicle preparations of the methano8enic strain Go1 were able to couple the reduction of the heterodisulfide of 2-mercaptoetbanesulfonate and 7-mercaptoheptanoylthreonine phosphate (CoM-99HTP) by H, with ATP formation. The rate of ATP synthesis was 1 mol/min mg protein. ATP synthesis and disulfide reduction were only observed with CoM-S-S-HTP, but not with CoM-4S-CoM or HTP-S-S-HTP. The methylreductase inhibitor 2-brorn~~~~ulfo~cacid had no effect on ATP synthesis induced by CoM-S-4HTP reduction with Hr. ATP synthesis was completely inhibited by the uncoupler SF 6847 whereas the con~mi~t CoM-S-S-HTP reduction was stimulated. The ATP synthase inhibitors DCCD and DES also inhibited ATP fo~ation completely and decreased the CoM-S-S-HTP reduction rate to 35% of the control. These ~bito~ effects were abolished by addition of the uncoupler. From these results it is concluded that energy couphng between the electron transfer from % to the heterodisultide and ATP synthesis occurs via a transmembrane proton gradient.

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Catalytic properties of the heterodisulfide reductase involved in the final step of methanogenesis

Cited by 50 publications

References 8 publications

Methane from acetate

Methane from acetate

H₂: heterodisulfide oxidoreductase complex from Methanobacterium thermoautotrophicum

ATP synthesis coupled to electron transfer from H₂ to the heterodisulfide of 2‐mercaptoethanesulfonate and 7‐mercaptoheptanoylthreonine phosphate in vesicle preparations of the methanogenic bacterium strain Gö1

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Catalytic properties of the heterodisulfide reductase involved in the final step of methanogenesis

Cited by 50 publications

References 8 publications

Methane from acetate

Methane from acetate

H2: heterodisulfide oxidoreductase complex from Methanobacterium thermoautotrophicum

ATP synthesis coupled to electron transfer from H2 to the heterodisulfide of 2‐mercaptoethanesulfonate and 7‐mercaptoheptanoylthreonine phosphate in vesicle preparations of the methanogenic bacterium strain Gö1

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H₂: heterodisulfide oxidoreductase complex from Methanobacterium thermoautotrophicum

ATP synthesis coupled to electron transfer from H₂ to the heterodisulfide of 2‐mercaptoethanesulfonate and 7‐mercaptoheptanoylthreonine phosphate in vesicle preparations of the methanogenic bacterium strain Gö1