Petunidin could form in the exocarp of fruits from delphinidin, with an anthocyanin flavonoid O-methyltransferase (Catechol-O-methyl transferase) catalyzing the B-ring methylation and S-Adenosyl-L-methyl-3H methionine being the methyl group donor.
Methyltransferases are also responsible for the addition of methyl groups to the 2' hydroxyls of the first and second nucleotides next to the 5' cap in messenger RNA.
The enzyme 3,7-dimethylquercetin 4'-O-methyltransferase uses S-adenosyl methionine and 5,3',4'-trihydroxy-3,7-dimethoxyflavone (rhamnazin) to produce S-adenosylhomocysteine and 5,3'-dihydroxy-3,7,4'-trimethoxyflavone (ayanin).
Creatine is synthesized primarily in the liver from the methylation of glycocyamine (guanidino acetate, synthesized in the kidney from the amino acids arginine and glycine) by S-adenosyl methionine.
metK genes encode methionine adenosyltransferase, which synthesizes S-adenosyl methionine (SAM), and ahcY genes encode S-adenosylhomocysteine hydrolase, which degrade the related metabolite S-Adenosyl-L-homocysteine (SAH).
The enzyme 8-hydroxyquercetin 8-O-methyltransferase uses S-adenosyl methionine and gossypetin to produce S-adenosylhomocysteine and 3,5,7,3',4'-pentahydroxy-8-methoxyflavone.
The enzyme 3-methylquercetin 7-O-methyltransferase uses S-adenosyl methionine and 5,7,3',4'-tetrahydroxy-3-methoxyflavone (isorhamnetin) to produce S-adenosylhomocysteine and 5,3',4'-trihydroxy-3,7-dimethoxyflavone (rhamnazin).
The enzyme 3,7-dimethylquercetin 4'-O-methyltransferase uses S-adenosyl methionine and rhamnazin to produce S-adenosylhomocysteine and ayanin.