Methyltransferase is an enzyme that catalyzes the transfer of a methyl group from a donor molecule to a recipient molecule. This process plays a critical role in a variety of biological processes, including gene regulation, protein function, and DNA repair. Methyltransferases are a diverse group of enzymes that can be found in all living organisms, from bacteria to humans. They are involved in adding methyl groups to a wide range of molecules, including DNA, RNA, proteins, and small molecules. Studying methyltransferases is important for understanding how these enzymes function, as well as their role in various diseases and potential therapeutic applications.