Coenzyme-B sulfoethylthiotransferase

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.[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) \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.[5] Such organisms are methanotrophs.

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

This enzyme participates in folate biosynthesis.

Structure

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,[6] also called McrA, McrB and McrG, respectively.

References

  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. http://microbewiki.kenyon.edu/index.php/Bovine_Rumen#Methanogens
  3. Whitford, M. F.; Teather, R. M.; Forster, R. J. (2001). "Phylogenetic analysis of methanogens from the bovine rumen". BMC microbiology 1: 5. PMC 32158. 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. 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. doi:10.1126/science.1100025. PMID 15353801.
  6. 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. doi:10.1126/science.278.5342.1457. PMID 9367957.

Further reading