||Methylation of proteins, nucleic acids and oligosaccharides is an important post-translational regulatory event. Activities that are methylation-related include meiosis, biosynthesis, development, signal transduction, chromatin regulation, and gene silencing. The enzymes that mediate the covalent transfer of a methyl group from a donor to an acceptor molecule are methyltransferases. Methyltransferases have structurally unrelated acceptors as diverse as proteins and DNA, however frequently use S-adenosylmethionine as a universal donor. Part of the acceptor diversity of this enzyme family relates to the flexible structural folds that bind these molecules in proximity of the donor. The side-chains of lysine, arginine, glutamate, glutamine, asparagines, and isoprenylated residues serve as methylation sites in proteins like histones. Changes in methylation patterns have been tightly linked to disease states such as cancer and vascular disease.