leucine (Leu) /lo̅o̅″sēn/ [Gk, leukos, white] , a white crystalline essential amino acid required for optimal growth in infants and nitrogen equilibrium in adults. It cannot be synthesized by the body and is obtained by the hydrolysis of food protein during digestion. An inherited defect in one of the enzymes involved in the process results in a rare disorder called maple syrup urine disease. See also amino acid, leucinosis, maple syrup urine disease.
