L-Methionine is one of the essential sulphur amino acids. New Roots L-Methionine contributes to the formation of numerous important compounds in your body. This process is called "methylation". In addition to its role as a precursor in protein synthesis, L-methionine participates in a wide range of biochemical reactions, including the production of S-adenosylmethionine (SAMe), L-cysteine, glutathione, taurine and sulfates.