Dimethylglycine N-methyltransferase (, BsmB, DMT) is an enzyme with systematic name S-adenosyl-L-methionine:N,N-dimethylglycine N-methyltransferase (betaine-forming). This enzyme catalyses the following chemical reaction
This enzyme is purified from the marine cyanobacterium Synechococcus sp. WH8102.