DNA Methyltransferases (EC 220.127.116.11 and EC 18.104.22.168)
DNA methyltransferases (Mtases) catalyze the transfer of the S-methyl group of S-adenosylmethionine (SAM) to deoxycytosine (dC) or deoxyadenine (dA) bases within defined DNA sequences (1). Individual enzymes are specific for one or the other base, and modify at the 6-NH2 of dA (EC 22.214.171.124) or at the N4 or 5-C position of dC (EC 126.96.36.199) depending on the particular enzyme (2). The reaction is predominantly irreversible. Enzymes, such as O 6-methylguanine DNA Mtase, that participate in DNA repair processes will not be discussed here.