Coenzyme B

Coenzyme B is a coenzyme required for redox reactions in methanogens. The full chemical name of coenzyme B is 7-thioheptanoylthreoninephosphate. The molecule contains a thiol, which is its principal site of reaction.

Coenzyme B reacts with 2-methylthioethanesulfonate, abbreviated CH3-S-CoM, to release methane in methanogenesis:
 * CH3-S-CoM + HS-CoB &rarr;  CH4  +  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:
 * CH3-S-CoM + HS-CoB -O2CCH=CHCO2- &rarr;  -O2CCH2-CH2CO2-  +  CoB-S-S-CoM