Methionine is a sulphur-containing amino acid and it is present in many protein molecules. In addition to methionine, cysteine also contains sulphur. Sulphur amino acid plays a very important role in immunity and metabolism.methionine and cysteine are precursors of S-adenosylmethionine, hydrogen sulfide, and glutathione. These compounds protect the tissue from the damage. The deficiency and excess of methionine and cysteine in diet affect the normal growth of animals.