DNA Methyltransferase
DNA methyltransferase (DNA MTase) family of enzymes catalyze the transfer of a methyl group to DNA. DNA methylation serves a wide variety of biological functions. All the known DNA methyltransferases use S-adenosyl methionine (SAM) as the methyl donor. Three active DNA methyltransferases have been identified in mammals. They are named DNMT1, DNMT3A, and DNMT3B. A fourth enzyme previously known as DNMT2 is not a DNA methyltransferase.