An essential amino acid and a key com- ponent of protein. Lack of arginine in the diet impairs growth, and in adult males it decreases the sperm count. Arginine is available in turkey, chicken, and other meats, and as L-arginine in sup- plements. Babies born without the enzyme phos- phate synthetase have arginine deficiency syndrome; adding arginine to their diets permits normal growth and development.