Coenzyme B
Template:Chembox Coenzyme B is a coenzyme required for redox reactions in methanogens. The full chemical name of coenzyme B is 7-mercaptoheptanoylthreoninephosphate.[1] The molecule contains a thiol, which is its principal site of reaction.
Coenzyme B reacts with 2-methylthioethanesulfonate (methyl-Coenzyme M, abbreviated Template:Chem/link), to release methane in methanogenesis:[2]
- Template:Chem/link + HS–CoB → Template:Chem/link + CoB–S–S–CoM
This conversion is catalyzed by the enzyme methyl coenzyme M reductase, which contains cofactor F430 as the prosthetic group.
A related conversion that utilizes both HS-CoB and HS-CoM is the reduction of fumarate to succinate, catalyzed by fumarate reductase:[3]
- HS–CoM + HS–CoB + −Template:Chem/link → −Template:Chem/link + CoB–S–S–CoM
Importance of coenzyme B in methanogenesis
Coenzyme B is an important component in the terminal step of methane biogenesis.[4] It acts as a two electron-donor to reduce coenzyme M (methyl-coenzyme) into two molecules a methane and a heterodisulfide.[5] Two separate experiments that were performed, one with coenzyme B and other without coenzyme B, indicated that using coenzyme B before the formation of the methane molecule, results in a more efficient and consistent bond cleavage.[6]
References
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