IUBMB Enzyme Nomenclature


Accepted name: ferredoxin:CoB-CoM heterodisulfide reductase

Reaction: 2 oxidized ferredoxin [iron-sulfur] cluster + CoB + CoM = 2 reduced ferredoxin [iron-sulfur] cluster + CoM-S-S-CoB + 2 H+

Glossary: CoB = coenzyme B = N-(7-mercaptoheptanoyl)threonine 3-O-phosphate = N-(7-thioheptanoyl)-3-O-phosphothreonine
CoM = coenzyme M = 2-sulfanylethane-1-sulfonate = 2-mercaptoethanesulfonate (deprecated)
CoM-S-S-CoB = CoB-CoM heterodisulfide = N-{7-[(2-sulfoethyl)dithio]heptanoyl}-O3-phospho-L-threonine

Other name(s): hdrABC (gene names); hdrA1B1C1 (gene names); hdrA2B2C2 (gene names)

Systematic name: CoB,CoM:ferredoxin oxidoreductase

Comments: HdrABC is an enzyme complex that is found in most methanogens and catalyses the reduction of the CoB-CoM heterodisulfide back to CoB and CoM. HdrA contains a FAD cofactor that acts as the entry point for electrons, which are transferred via HdrC to the HdrB catalytic subunit. One form of the enzyme from Methanosarcina acetivorans (HdrA2B2C2) can also catalyse EC, coenzyme F420:CoB-CoM heterodisulfide,ferredoxin reductase. cf. EC, H2:CoB-CoM heterodisulfide,ferredoxin reductase, EC, formate:CoB-CoM heterodisulfide,ferredoxin reductase, and EC, dihydromethanophenazine:CoB-CoM heterodisulfide reductase.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Buan, N.R. and Metcalf, W.W. Methanogenesis by Methanosarcina acetivorans involves two structurally and functionally distinct classes of heterodisulfide reductase. Mol. Microbiol. 75 (2010) 843-853. [PMID: 19968794]

2. Yan, Z., Wang, M. and Ferry, J.G. A ferredoxin- and F420H2-dependent, electron-bifurcating, heterodisulfide reductase with homologs in the domains Bacteria and Archaea. mBio 8 (2017) e02285-16. [PMID: 28174314]

[EC created 2017]

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