Reductive activation of methanol: 5-hydroxybenzimidazolylcobamide methyltransferase of Methanosarcina barkeri.

Methanol: 5-hydroxybenzimidazolylcobamide methyltransferase (MT1) from Methanosarcina barkeri, which is one of the enzymes responsible for the transmethylation from methanol to coenzyme M, was found to be activated in the presence of hydrogenase and ferredoxin. This activation was shown to involve a reduction of the bound corrinoid to the Co (I) level, and was demonstrated by spectrophotometry and chemical conversion of reduced MT1 to its methylated form. The reducing system of hydrogenase and ferredoxin was able to reduce dithiols, like dithiodiethanesulfonate and cystine to their monomers, in the presence of a corrinoid, which acts as an electron carrier. The ferredoxin was purified 133-fold and was tentatively identified on the basis of spectral properties and iron content of 3.8-4.0 atoms iron per molecule ferredoxin (12,000 daltons).