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

Chemotaxis

Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...

 signal transduction

Signal transduction

Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...

.

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

Chemotaxis

Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...

 regulation.
CheB is more specifically termed a methylesterase

Esterase

An esterase is a hydrolase enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis.A wide range of different esterases exist that differ in their substrate specificity, their protein structure, and their biological function.- EC classification/list...

, as it removes methyl groups from methylglutamate

Methylglutamate

A modified form of glutamate....

 thus creating glutamic acid

Glutamic acid

Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...

 residues accompanied by the release of methanol

Methanol

Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

.

Oxidative demethylation

Methylated lysine

Lysine

Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....

 residues can be demethylated through oxidation and release of formaldehyde

Formaldehyde

Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

, either using oxygen (EC 1.14.11.27) or FAD

FAD

In biochemistry, flavin adenine dinucleotide is a redox cofactor involved in several important reactions in metabolism. FAD can exist in two different redox states, which it converts between by accepting or donating electrons. The molecule consists of a riboflavin moiety bound to the phosphate...

 (EC 1.5.8.-) as electron donor

Electron donor

An electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process....

s.

Sources

• Madigan, Michael. Brock's Biology of Microorganisms, 11 ed.
• Park, Borbat, et al. Reconstruction of the chemotaxis receptor-kinase assembly, Nature Structural & Molecular Biology 13, 400-407 (2006). 23 April 2006