INVOLVEMENT OF METHYLTRANSFERASE-ACTIVATING PROTEIN AND METHYLTRANSFERASE-2 ISOENZYME-II IN METHYLAMINE-COENZYME-M METHYLTRANSFERASE REACTIONS IN METHANOSARCINA-BARKERI FUSARO

The enzyme systems involved in the methyl group transfer from methanol and from tri- and dimethylamine to 2-mercaptoethanesulfonic acid (coe nzyme M) were resolved from cell extracts of Methanosarcina barkeri Fu saro grown methanol and trimethylamine, respectively. Resolution was a ccomplished by ammonium sulfate fractionation, anion-exchange chromato graphy, and fast protein liquid chromatography. The methyl group trans fer reactions from tri- and dimethylamine, as well as the monomethylam ine:coenzyme M methyltransferase reaction, were strictly dependent on catalytic amounts of ATP and on a protein present in the 65% ammonium sulfate supernatant, The latter could be replaced by methyltransferase -activating protein isolated from methanol-grown cells of the organism . In addition, the tri- and dimethylamine:coenzyme M methyltransferase reactions required the presence of a methylcobalamin:coenzyme M methy ltransferase (MT(2)), which is different from the analogous enzyme fro m methanol-grown M. barkeri. In this work, it is shown that the variou s methylamine:coenzyme M methyltransfer steps proceed in a fashion whi ch is mechanistically similar to the methanol:coenzyme M methyl transf er, get with the participation of specific corrinoid enzymes and a spe cific MT(2) isoenzyme.