demethylated

Demethylated is the past participle and adjective referring to the removal of methyl groups (−CH3) from a molecule. Demethylation is a common chemical transformation and a key mechanism in biology for regulating gene activity and epigenetic states.

In chemistry, demethylation describes reactions that convert methyl-containing substrates into products with fewer methyl groups. Commonly, methyl ethers are hydrolyzed to remove methyl groups as methanol, or other methylated amines are demethylated by acids, reductants, or catalytic systems. Reagents and conditions vary by substrate, selectivity, and reaction conditions.

In biology, DNA demethylation refers to the loss or removal of methyl groups at cytosine residues, especially at the 5-position to form unmethylated cytosine. This process is central to epigenetic regulation, development, and cellular reprogramming. Active demethylation involves oxidation of 5-methylcytosine by TET enzymes and subsequent base excision repair, while passive demethylation occurs during DNA replication when maintenance methylation is reduced.

Histone demethylation refers to removal of methyl groups from histone tails, altering chromatin structure and gene expression. Enzymes such as LSD1 and JmjC-domain-containing demethylases catalyze this reaction, acting on lysine or arginine residues.

The term demethylated applies to molecules after one or more methyl groups have been removed, and it is used across chemistry, biochemistry, and genetics to describe state changes that influence reactivity and regulation.