The SET and MYND (SMYD) proteins are lysine methyltransferases that catalyse the addition of one or more methyl groups, using S-adenosyl-l-methionine (SAM) as a cofactor, to the amino group of a lysine residue in the substrate resulting in a mono, di, or trimethylated lysine and the cofactor by-product S-adenosyl-l-homocysteine (SAH). (Adapted from PMID:27447830).