Presents an overview of the AdoMet-dependent methyltransferases, with emphasis on structure-function relationships. S-adenosyl-L-methionine (AdoMet) is the second most commonly used enzyme cofactor after ATP. The AdoMet-dependent methyltransferases act on a variety of target molecules, including DNA, RNA, protein, polysaccharides, lipids and a range of small molecules. The well-conserved architecture of these enzymes, and the implications of this conservation for their evolutionary history, are major themes of the book. The 13 chapters describe the structures, enzyme kinetics and biological roles of the AdoMet-dependent methyltransferases from a wide range of cell types: plant, animal, bacterial and archaeal.