Demethylase

Demethylases are enzymes that remove methyl (CH3-) groups from proteins and other substances. They are used in a variety of processes, such as in chemotaxis signal transduction.

Hydrolytic demethylation
A good example of a demethylase is the activated (i.e. phosphorylated) form of the CheB protein (EC 3.1.1.61), which demethylates MCPs (methyl-accepting chemotaxis proteins). MCPs sense extracellular attractants and repellents in bacteria like E. coli in chemotaxis regulation. CheB is more specifically termed a methylesterase, as it removes methyl groups from methylglutamate thus creating glutamic acid residues accompanied by the release of methanol.

Oxidative demethylation
Methylated lysine residues can be demethylated through oxidation and release of formaldehyde, either using oxygen (EC 1.14.11.27) or FAD (EC 1.5.8.-) as electron donors.