Methionine: Methionine, cysteine, and cystine are the sulphur containing amino acids of the body. All are glycogenic. Methionine is essential amino acid, whereas the cysteine and cystine are not. Methionine is amino-methyl-thiobutyric acid. This is to be given in diet, or can be substituted with its corresponding keto acids, which cannot be synthesized in the body but on amination gives rise to methionine. The methionine can be synthesized in the micro-organism by methylating the homocysteine.

Three amino acids methionine, arginine, and glycine are directly involved in synthesis of cretine. First arginine and glycine help in formation of glycocyamine in kidney, which then is methylated by active methionine in the liver to complete the synthesis of creatine.

The catabolism of methionine leads to succinyl-CoA and CO2. The methionine takes part in the metabolic functions as methyl donor, in synthesis of cysteine and homoserine, and in formation of keto methyl thiobutyric acid.

It can make choline in aid of vitamin B-12. It acts as an antioxidant. It keeps liver healthy. It checks fat and cholesterol. It maintains nitrogen balance in the body.

It is found mainly in whole milk powder, cheese, curd, milk egg, pork, peaches, grapes, watermelon seeds, sunflower and sesame seeds, cauliflower, bitter gourd, sweet potato, carrot and celery leaves, barely, millet, ragi, rice, and wheat. The RDA for children is 22 mg, and for adults is 13 mg per kg. body weight.

Lysine: Lysine is an essential amino acid, as it cannot be synthesized in the body. It eliminates virus infections in combination with vitamin C, A and zinc. Its deficiency can cause poor appetite, weight loss, anaemia, and low concentration.

It is a daminocaproic acid and cannot be synthesized in the body. It is essential for growth. Lysine is synthesized in plants and micro-organism. In the yeast, it is synthesized from acetate and ketoglutarate. In the bacteria, it is synthesized from aspirate and pyruvate. Lysine is a ketogenic amino acid.

Lysine checks spreading of viruses. It eliminates virus infection in combination with zinc, and vitamin A & C. Vitamin C makes lysine more powerful in controlling virus effects. The deficiency can cause poor appetite, weight loss, anaemia, low concentration, and cold ailments. It promotes recovery in herpes.

It is available is apple, mango, papaya, beef, pork, milk, curd, cheese, dry yeast, bottle gourd, cauliflower, jack fruit, cashew nut, pistachio, sunflower seeds, bathua, spinach, beetroot, potato, soyabean, redgram, rajmah, dry peas, lentil, green gram, cow pea, bengal gram, wheat, rice, and barley. The RDA for children is 44 mg, and for adults is 12 mg per kg. body weight.