Methylase

A methylase is an enzyme that attaches a methyl group to a molecule.

These are found in prokaryotes and eukaryotes. Bacteria use methylase to differentiate between foreign genetic material and their own, thus protecting their DNA from their own immune system. By placing a methyl group on a base of the recognition site of a restriction endonuclease, methylases prevent the enzyme from cleaving the bacterial DNA.

There are methylases that can methylate DNA, RNA, proteins, or small molecules, for example, DNA methyltransferase, which methylates cytosine residues and adenine residues in DNA.

See also: Demethylase