methylating

Methylating is the chemical process of introducing a methyl group (−CH3) into another molecule. The transfer can target oxygen, nitrogen, sulfur, or carbon atoms, producing O-, N-, S-, or C-methylated products. In organic synthesis, methylation is used to modify reactivity, protect functional groups, or tune physical properties of compounds. Common methylating agents include methyl iodide, dimethyl sulfate, dimethyl carbonate, and related reagents. In biological systems, S-adenosylmethionine (SAM) functions as the principal methyl donor, with enzymes called methyltransferases catalyzing the transfer under physiological conditions.

In biochemistry and molecular biology, methylation is a key mechanism of gene regulation and epigenetics. DNA methylation typically involves the addition of a methyl group to the 5-position of cytosine in CpG dinucleotides, catalyzed by DNA methyltransferases. This modification can repress gene transcription and influence processes such as development, genomic imprinting, and X-chromosome inactivation. Histone methylation, carried out by histone methyltransferases, modulates chromatin structure and the accessibility of genes, contributing to the dynamic regulation of gene expression.

Methylation also affects metabolism, pharmacology, and toxicology. In drug metabolism, methylation can alter a compound’s activity, lipophilicity, and routes of excretion. Aberrant DNA methylation patterns are associated with various diseases, including cancer; therapies that target methyltransferases or related demethylation pathways are an area of medical research and clinical use. Overall, methylation is a versatile and widespread chemical modification with diverse biological and practical implications.