| coenzyme-B sulfoethylthiotransferase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 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 / 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.
Contents
The enzyme has two active sites, each occupied by the nickel-containing F430 cofactor. [4]
- + ⇌ CoM-S-S-CoB + methane
 |  |
The two substrates of this enzyme are 2-(methylthio)ethanesulfonate and N-(7-mercaptoheptanoyl)threonine 3-O-phosphate; 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.
