The following cytoplasmic vertebrate methyltransferases are evolutionary related [1,2]:

• Nicotinamide N-methyltransferase (EC 2.1.1.1) (NNMT). NNMT catalyzes the N- methylation of nicotinamide and other pyridines to form pyridinium ions. This activity is important for the biotransformation of many drugs and xenobiotic compounds.
• Phenylethanolamine N-methyltransferase (EC 2.1.1.28) (PNMT). PNMT catalyzes the last step in catecholamine biosynthesis, the conversion of noradrenalin to adrenalin.
• Indolethylamine N-methyltransferase (EC 2.1.1.49) (INMT).
• Thioether S-methyltransferase (EC 2.1.1.96) (TEMT). TEMT catalyzes the methylation of dimethyl sulfide into trimethylsulfonium.

These enzymes use S-adenosyl-L-methionine as the methyl donor. They are proteins of 30 to 32 Kd. As a signature pattern we selected the most conserved region, a stretch of 16 residues which are located in the N-terminal section of these enzymes.