Coenzyme-B sulfoethylthiotransferase

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coenzyme-B sulfoethylthiotransferase
EC number
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO

In enzymology, coenzyme-B sulfoethylthiotransferase, also known as methyl-coenzyme M reductase (MCR) or most systematically as 2-(methylthio)ethanesulfonate:N-(7-thioheptanoyl)-3-O-phosphothreonine S-(2-sulfoethyl)thiotransferase is an enzyme that catalyzes the final step in the formation of methane.[1] It does so by combining the hydrogen donor coenzyme B and the methyl donor coenzyme M. Via this enzyme, most of the natural gas on earth was produced. Ruminants (e.g. cows) produce methane because their rumens contain methanogenic prokaryotes (Archaea)[2][3] that encode and express the set of genes of this enzymatic complex.

The enzyme has two active sites, each occupied by the nickel-containing F430 cofactor.[4]

2-(methylthio)ethanesulfonate (methyl-CoM) + N-(7-mercaptoheptanoyl)threonine 3-O-phosphate (coenzyme B) CoM-S-S-CoB + methane

Thus, the two substrates of this enzyme are 2-(methylthio)ethanesulfonate and N-(7-mercaptoheptanoyl)threonine 3-O-phosphate, whereas its two products are CoM-S-S-CoB and methane. 3-Nitrooxypropanol inhibits the enzyme.[5]

In some species, the enzyme reacts in reverse (a process called reverse methanogenesis), catalysing the anaerobic oxidation of methane, therefore removing it from the environment.[6] Such organisms are methanotrophs.

This enzyme belongs to the family of transferases, specifically those transferring alkylthio groups.

This enzyme participates in folate biosynthesis.[citation needed]


Coenzyme-B sulfoethylthiotransferase is a multiprotein complex made up of a pair of identical halves. Each half is made up of three subunits: α, β and γ,[7] also called McrA, McrB and McrG, respectively.


  1. ^ Stephen W., Ragdale (2014). "Chapter 6. Biochemistry of Methyl-Coenzyme M Reductase: The Nickel Metalloenzyme that Catalyzes the Final Step in Synthesis and the First Step in Anaerobic Oxidation of the Greenhouse Gas Methane". In Peter M.H. Kroneck and Martha E. Sosa Torres. The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment. Metal Ions in Life Sciences. 14. Springer. pp. 125–145. doi:10.1007/978-94-017-9269-1_6. 
  2. ^
  3. ^ Whitford, M. F.; Teather, R. M.; Forster, R. J. (2001). "Phylogenetic analysis of methanogens from the bovine rumen". BMC microbiology. 1: 5. PMC 32158Freely accessible. PMID 11384509. 
  4. ^ Thauer, R. K., "Biochemistry of methanogenesis: a tribute to Marjory Stephenson", Microbiology, 1998, 144, 2377-2406. doi:10.1099/00221287-144-9-2377 PMID 9782487
  5. ^ Hristov, A. N., et al., "An inhibitor persistently decreased enteric methane emission from dairy cows with no negative effect on milk production", Proc. Natl. Acad. Sci. U. S. A. 2015, volume 112, 10663-10668. doi:10.1073/pnas.1504124112
  6. ^ Hallam, S. J.; Putnam, N.; Preston, C. M.; Detter, J. C.; Rokhsar, D.; Richardson, P. M.; Delong, E. F. (2004). "Reverse Methanogenesis: Testing the Hypothesis with Environmental Genomics". Science. 305 (5689): 1457–1462. PMID 15353801. doi:10.1126/science.1100025. 
  7. ^ Ermler, U.; Grabarse, W.; Shima, S.; Goubeaud, M.; Thauer, R. K. (1997). "Crystal structure of methyl-coenzyme M reductase: The key enzyme of biological methane formation". Science. 278 (5342): 1457–1462. PMID 9367957. doi:10.1126/science.278.5342.1457. 

Further reading[edit]

  • Bobik TA, Olson KD, Noll KM, Wolfe RS (1987). "Evidence that the heterodisulfide of coenzyme M and 7-mercaptoheptanoylthreonine phosphate is a product of the methylreductase reaction in Methanobacterium". Biochem. Biophys. Res. Commun. 149 (2): 455–60. PMID 3122735. doi:10.1016/0006-291X(87)90389-5. 
  • Ellermann J, Hedderich R, Boecher R, Thauer RK (1988). "The final step in methane formation: investigations with highly purified methyl coenzyme M reductase component C from Methanobacterium thermoautotrophicum (strain Marburg)". Eur. J. Biochem. 184 (1): 63–68. PMID 2506016. doi:10.1111/j.1432-1033.1989.tb14990.x. 
  • Signor L, Knuppe C, Hug R, Schweizer B, Pfaltz A, Jaun B (2000). "Methane formation by reaction of a methyl thioether with a photo-excited nickel thiolate--a process mimicking methanogenesis in archaea". Chemistry. 6 (19): 3508–16. PMID 11072815. doi:10.1002/1521-3765(20001002)6:19<3508::AID-CHEM3508>3.3.CO;2-N.