In biological systems, methylation is catalyzed by enzymes; such methylation can be involved in modification of heavy metals, regulation of gene expression, regulation of protein function, and RNA processing. In vitro methylation of tissue samples is also one method for reducing certain histological staining artifacts. The counterpart of methylation is called demethylation.
In biological systems, methylation is accomplished by enzymes; methylation can modify heavy metals, regulate gene expression, RNA processing and protein function. It has been recognized as a key process underlying epigenetics.
Methanogenesis, the process that generates methane, is the result of a series of methylation reactions. These reactions are affected by a set of enzymes harbored by a family of anaerobic microbes.
In reverse methanogenesis, methane serves as the methylating agent.
A wide variety of phenols undergo O-methylation to give anisole derivatives. This process, catalyzed by enzymes such as caffeoyl-CoA O-methyltransferase, is a key reaction in the biosynthesis of lignols, percursors to lignin, a major structural component of plants.