Genetics Question Phenylketonuria occurs when the gene for t

Genetics Question

Phenylketonuria occurs when the gene for the enzyme phenylalanine hydroxylase is mutated, leading to an undesirable build-up of the compound usually acted upon by phenylalanine hydroxylase. Based on what you know about the metabolic pathway involving this enzyme, what dietary changes do you presume phenylketonurics must make? Phenylketonurics should eat reduced amounts of phenylalanine and increased amounts of tyrosine Phenylketonurics should eat additional phenylalanine and reduced amounts of tyrosine. No dietary changes are required. Phenylketoneurics must increase their intake of phenylalanine, no change to tyrosine intake is required. Phenylketonurics must reduce their intake of phenylalanine, no change to tyrosine intake is required.

Solution

Answer:

Phenylketonurics should eat reduced amounts of phenylalanine and incresed amounts of tyrosine.

The enzyme phenylalanine hydroxylase normally converts the amino acid phenylalanine into the amino acid tyrosine. If this reaction does not take place, phenylalanine accumulates and tyrosine is deficient.

People must adhere to a special diet low in Phe for optimal brain development. Since Phe is necessary for the synthesis of many proteins, it is required for appropriate growth, but levels must be strictly controlled. Tyrosine is a conditionally essential amino acid for PKU patients because without PAH it cannot be produced in the body through the breakdown of phenylalanine. Tyrosine is necessary for the production of neurotransmitters like epinephrine, norepinephrine, and dopamine. If the patient is suffering from hyperphenylalaninemia may have a deficiency of tyrosine (which is created from phenylalanine by PAH), must be supplemented with tyrosine to account for this deficiency.