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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)〔http://microbewiki.kenyon.edu/index.php/Bovine_Rumen#Methanogens〕 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.〔(Thauer, R. K., "Biochemistry of methanogenesis: a tribute to Marjory Stephenson", Microbiology, 1998, 144, 2377-2406. ) PMID 9782487〕 :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. 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. 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, also called McrA, McrB and McrG, respectively. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Coenzyme-B sulfoethylthiotransferase」の詳細全文を読む スポンサード リンク
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