FIG 5.
The methyl reductive methanogenic pathway in Methanosarcina. In this pathway, methyl groups are transferred to coenzyme M by the sequential action of methyltransferases MT1 and MT2 and then reduced to CH4 by coenzyme B, which forms a disulfide of CoM and CoB. Regeneration of CoM and CoB by the reduction of CoM-CoB occurs at the heterodisulfide reductase enzyme with electrons from reduced methanophenazine. The Vht hydrogenase generates MPred with electrons derived from the oxidation of H2. Portions of the core methanogenic pathway that are not used by the methyl reduction pathway, including Ech and Frh, are shown in light gray.