Reductive activation of the corrinoid-containing enzyme involved in methyl group transfer between methyl-tetrahydromethanopterin and coenzyme M in Methanosarcina barkeri.

The conversion of methyl-tetrahydromethanopterin to methylcoenzyme M in Methanosarcina barkeri is catalyzed by two enzymes: an enzyme with a bound corrinoid, which becomes methylated during the reaction and an enzyme which transfers the methyl group from this corrinoid to coenzyme M. As in the similar methyltransfer reaction in Methanobacterium thermoautotrophicum the corrinoid enzyme in M barkeri needs to be activated by H2 and ATP. ATP can be replaced by Ti(III)citrate or CO.