Proposed pathway for the oxidation of chloromethane to formate based on DNA sequence data and biochemical analysis. CmuA, methyltransferase I; CmuB, methyltransferase II; MetF, putative 5,10-methylene-H4folate reductase; FolD, putative 5,10-methylene-H4folate dehydrogenase/5,10-methenyl-H4folate cyclohydrolase; PurU, putative 10-formyl-H4folate hydrolase. The corrinoid protein acting as the primary methyl acceptor and thought to be part of CmuA is indicated by CoI-E.