Overview for MACiE Entry M0156

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General Information

EC Number: (A member of the Transferases, Transferring sulfur-containing groups, Transferring alkylthio groups)

Enzyme Name: coenzyme-B sulfoethylthiotransferase

Biological Species: Methanobacterium thermoautotrophicum (Bacteria)

Catalytic Chain UniprotKB Accession Codes:

  • P11558 - Methyl-coenzyme M reductase I subunit alpha
  • P11560 - Methyl-coenzyme M reductase I subunit beta

Representative PDB Code: 1mro - METHYL-COENZYME M REDUCTASE (Resolution = 1.16 Å).

Catalytic CATH Codes:

"Other" CATH Codes:

Display structure information

Overall Reaction:

Image of 2-(methylthio)ethanesulfonate

Image of N-(7-mercaptoheptanoyl)threonine 3-O-phosphate

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Image of coenzyme M 7-mercaptoheptanoylthreonine-phosphate heterodisulfide

Image of methane

N-(7-mercaptoheptanoyl)threonine 3-O-phosphate
coenzyme M 7-mercaptoheptanoylthreonine-phosphate heterodisulfide

This reaction is irreversible.

Overall Comment: There are at least two proposed alternative mechanisms for this reaction. The mechanism depicted here is better supported by stereochemical and energetic factors [1,3]. However it should be noted that it is still unclear which mechanism is the correct one [4]. The second mechanism proposed assumes that the first step is the attack by the Ni(I) on the thioether sulfur of methyl-coenzyme M. This yields a free methyl radical which reacts with the thiol group of coenzyme B to give methane and the coenzyme B thiyl radical [2]. Ni is from the hydroporphinoid nickel complex coenzyme Factor 430.

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Stepwise Description of the Reaction

Step 1Nickel (Ni(I)) of factor 430 attacks the methyl group of the methylated coenzyme M, which is reprotonated from Tyr367E. Nickel assumed the Ni(III) oxidation state.
Step 2Tyr367E deprotonates coenzyme M, causing it to donate a single electron to the Ni(III) ion of factor 430.
Step 3The methyl group deprotonates Tyr367E whilst disassociating from Ni(II) in factor 430. Tyr367E immediately deprotonates coenzyme B.
Step 4The thiolate of coenzyme B attacks the thiyl radical of coenzyme M in a coordination reaction.
Step 5The thiyl radical of coenzyme M donates a second electron to the nickel of factor 430, regenerating the Ni(I) oxidation state.

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Catalytic Residues Involved

Type Number Chain Location of Function
Gln 147 A Side Chain
Tyr 367 E Side Chain

Organic Cofactors for M0156

Type Identity Chain
Coenzyme B TP7 9000 Overview
Coenzyme M COM 9700 Overview

Metal Cofactors for M0156

Type Het group Number Chain
nickel F43 700 x Overview


  1. W. Grabarse et al. (2001), J. Mol. Biol., 309, 315-330. On the mechanism of biological methane formation: structural evidence for conformational changes in methyl-coenzyme M reductase upon substrate binding.
    Medline: 11491299
  2. V. Pelmenschikov et al. (2002), J. Am. Chem. Soc., 124, 4039-4049. A mechanism from quantum chemical studies for methane formation in methanogenesis.
    Medline: 11942842
  3. M. Goenrich et al. (2004), J. Biol. Inorg. Chem., 9, 691-705. Probing the reactivity of Ni in the active site of methyl-coenzyme M reductase with substrate analogues.
    Medline: 15365904
  4. U. Ermler (2005), Dalton Trans., 21, 3451-3458. On the mechanism of methyl-coenzyme M reductase.
    Medline: 16234924

Homologue information for M0156 (1mro)

CSA Homologues

MACiE Homologues (within the PDB)

MACiE Homologues (within UniprotKB/SwissProt)

Links to this entry in other databases

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GOA logo
methanogenesis (biological process)
transferase activity (molecular function)
metal ion binding (molecular function)
coenzyme-B sulfoethylthiotransferase activity (molecular function)