L-Methionine

An essential, sulfur-containing amino acid and precursor to other important metabolites such as cysteine, taurine, carnitine, various phospholipids and S-adenosyl-methionine (SAM-e).  The latter serves as a methyl donor for important biochemical reactions (such as methylation of DNA). Methionine also metabolizes to homocysteine, a risk factor for cardiovascular disease.