Methionine is an intermediate in the biosynthesis of Cystein, Carnitine, Taurine, Lecithin, Phosphatidylcholine and other phospholipids. This amino acid is also used by plants for synthesis of ethylene. The process is known as the Yang Cycle or the methionine cycle. As an essential amino acid, methionine is not synthesized de novo in humans, who must ingest methionine or methionine-containing proteins. Although mammals cannot synthesize methionine, they can still use it in a variety of biochemic