Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
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2 oxidized coenzyme F420 + 2 reduced ferredoxin [iron-sulfur] cluster + CoB + CoM + 2 H+ | Methanosarcina acetivorans | - |
2 reduced coenzyme F420 + 2 oxidized ferredoxin [iron-sulfur] cluster + CoM-S-S-CoB | - |
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Organism | UniProt | Comment | Textmining |
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Methanosarcina acetivorans | - |
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Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|
2 oxidized coenzyme F420 + 2 reduced ferredoxin [iron-sulfur] cluster + CoB + CoM + 2 H+ | - |
Methanosarcina acetivorans | 2 reduced coenzyme F420 + 2 oxidized ferredoxin [iron-sulfur] cluster + CoM-S-S-CoB | - |
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Synonyms | Comment | Organism |
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hdrA2B2C2 | - |
Methanosarcina acetivorans |
Cofactor | Comment | Organism | Structure |
---|---|---|---|
coenzyme F420 | - |
Methanosarcina acetivorans | |
Ferredoxin | - |
Methanosarcina acetivorans |
General Information | Comment | Organism |
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metabolism | reduction of the disulfide of coenzyme M and coenzyme B (CoMS-SCoB) by heterodisulfide reductases (HdrED and HdrABC) is the final step in all methanogenic pathways. Flavin-based electron bifurcation (FBEB) by soluble HdrABC homologues play additional roles in driving essential endergonic reactions at the expense of the exergonic reduction of CoMS-SCoM. In the first step of the CO2 reduction pathway, HdrABC complexed with hydrogenase or formate dehydrogenase generates reduced ferredoxin (Fdx2-) for the endergonic reduction of CO2 coupled to the exergonic reduction of CoMS-SCoB dependent on FBEB of electrons from H2 or formate. Roles for HdrABC:hydrogenase complexes are also proposed for pathways wherein the methyl group of methanol is reduced to methane with electrons from H2. The HdrABC complexes catalyze FBEB-dependent oxidation of H2 for the endergonic reduction of Fdx driven by the exergonic reduction of CoMS-SCoB. The Fdx2- supplies electrons for reduction of the methyl group to methane. In H2- independent pathways, three-fourths of the methyl groups are oxidized producing Fdx2- and reduced coenzyme F420 (F420H2). The F420H2 donates electrons for reduction of the remaining methyl groups to methane requiring transfer of electrons from Fdx2- to F420. When switched from growth with methanol to growth with acetate, Methanosarcina acetivorans upregulates an electron bifurcating heterodisulfide reductase (HdrA2B2C2) that oxidizes F420H2 and reduces Fdx driven by reduction of CoMS-SCoB. A role has been proposed for sHdrA2B2C2 dependent on reduction of NAD-like coenzyme F420 (F420) by the Rnf complex analogous to Fdx-dependent reduction of NADC by homologous Rnf complexes from the domain Bacteria. In this way, Fdx reduced by HdrA2B2C2 is re-oxidized by Rnf thereby supplementing the translocation of Na+. HdrA2B2C2 is involved in reverse methanogenesis | Methanosarcina acetivorans |
physiological function | The HdrABC complexes catalyze FBEB-dependent oxidation of H2 for the endergonic reduction of Fdx driven by the exergonic reduction of CoMS-SCoB. The Fdx2- supplies electrons for reduction of the methyl group to methane. In H2- independent pathways, three-fourths of the methyl groups are oxidized producing Fdx2- and reduced coenzyme F420 (F420H2). The F420H2 donates electrons for reduction of the remaining methyl groups to methane requiring transfer of electrons from Fdx2- to F420. HdrA1B1C1 is proposed to catalyze FBEB-dependent oxidation of Fdx2- for the endergonic reduction of F420 driven by the exergonic reduction of CoMS-SCoB. When switched from growth with methanol to growth with acetate, Methanosarcina acetivorans upregulates an electron bifurcating heterodisulfide reductase (HdrA2B2C2) that oxidizes F420H2 and reduces Fdx driven by reduction of CoMS-SCoB. A role has been proposed for HdrA2B2C2 dependent on reduction of NAD-like coenzyme F420 (F420) by the Rnf complex analogous to Fdx-dependent reduction of NADC by homologous Rnf complexes from the domain Bacteria | Methanosarcina acetivorans |