Final answer:
PKU is caused by a defect in the enzyme phenylalanine hydroxylase, leading to an inability to metabolize phenylalanine, which causes brain damage and intellectual disabilities if not managed by a strict low-phenylalanine diet.
Step-by-step explanation:
PKU is caused by a defect in an enzyme that is needed to metabolize the essential amino acid phenylalanine. Phenylketonuria (PKU) is a genetic disorder that affects 1 in every 15,000 births in the United States. It is caused by insufficient activity or a defect in the enzyme known as phenylalanine hydroxylase, which is crucial for converting phenylalanine into tyrosine, another amino acid.
Individuals with PKU are unable to break down phenylalanine effectively, resulting in high levels of this amino acid in the body, which can be toxic and lead to damage to the brain and central nervous system. Symptoms of PKU can include intellectual disability, hyperactivity, seizures, and other neurological issues. Since tyrosine cannot be synthesized adequately by people with PKU, it becomes a conditionally essential amino acid and must be obtained through diet. Treatment involves a strict low-phenylalanine diet, which also requires avoiding aspartame, an artificial sweetener that contains phenylalanine.
The importance of early detection and dietary management cannot be overstated; newborns in the United States and Canada are routinely tested for PKU. If treated early with a modified diet, the severity of symptoms can be greatly reduced. For individuals with PKU, adherence to a diet low in phenylalanine is crucial for preventing brain damage and intellectual disabilities.