Coenzyme-B sulfoethylthiotransferase

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coenzyme-B sulfoethylthiotransferase
Identifiers
EC number 2.8.4.1
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

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. 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)[1][2] 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.[3]

2-(methylthio)ethanesulfonate (methyl-CoM) + N-(7-mercaptoheptanoyl)threonine 3-O-phosphate (coenzyme B) \rightleftharpoons 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.

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.[4] 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]

Structure[edit]

coenzyme-B sulfoethylthiotransferase is a protein complex made up of a pair of identical halves. Each half up of 3 subunits: α, β and γ,[5] also called McrA, McrB and McrG, respectively.

References[edit]

  1. ^ http://microbewiki.kenyon.edu/index.php/Bovine_Rumen#Methanogens
  2. ^
    1. REDIRECT Template:Cite pmid
  3. ^ 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
  4. ^
    1. REDIRECT Template:Cite pmid
  5. ^
    1. REDIRECT Template:Cite pmid

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. doi:10.1016/0006-291X(87)90389-5. PMID 3122735. 
  • Ellermann J, Hedderich R, Boecher R and 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. doi:10.1111/j.1432-1033.1989.tb14990.x. PMID 2506016. 
  • 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. doi:10.1002/1521-3765(20001002)6:19<3508::AID-CHEM3508>3.3.CO;2-N. PMID 11072815.