InterPro domain: IPR016461

Methyltransferases (EC [intenz:2.1.1.-]) constitute an important class of enzymes present in every life form. They transfer a methyl group most frequently from S-adenosyl L-methionine (SAM or AdoMet) to a nucleophilic acceptor such as oxygen leading to S-adenosyl-L-homocysteine (AdoHcy) and a methylated molecule [ 1 , 2 , 3 ]. All these enzymes have in common a conserved region of about 130 amino acid residues that allow them to bind SAM [ 4 ]. The substrates that are methylated by these enzymes cover virtually every kind of biomolecules ranging from small molecules, to lipids, proteins and nucleic acids [ 5 , 5 , 5 ]. Methyltransferase are therefore involved in many essential cellular processes including biosynthesis, signal transduction, protein repair, chromatin regulation and gene silencing [ 5 , 5 , 5 ]. More than 230 families of methyltransferases have been described so far, of which more than 220 use SAM as the methyl donor.

The vast majority of methyltransferases belong to the Rossmann-like fold (Class I) which consists in a seven-stranded beta sheet adjoined by alpha helices. Even within the structurally conserved family of Class I methyltransferases, a wide variety of mechanisms have evolved to activate the catalytic nucleophile, dependent on the polarizability of the target atom [ 5 ].

Proteins in this entry belong to the Class I SAM-dependent methyltransferases superfamily, including caffeic acid O-methyltransferase (COMT), isoflavone-7-O-methyltransferase, inositol 4-methyltransferase and acetylserotonin O-methyltransferase [ 5 ].

1. Natural history of S-adenosylmethionine-binding proteins. BMC Struct. Biol. 5, 19
2. Comprehensive structural and substrate specificity classification of the Saccharomyces cerevisiae methyltransferome. PLoS ONE 6, e23168
3. Many paths to methyltransfer: a chronicle of convergence. Trends Biochem. Sci. 28, 329-35
4. Universal catalytic domain structure of AdoMet-dependent methyltransferases. J. Mol. Biol. 247, 16-20