Final answer:
Patients with PKU need to supplement with tyrosine to support catecholamine production due to their inability to convert phenylalanine into tyrosine adequately.
Step-by-step explanation:
Patients with Phenylketonuria (PKU), a condition caused by a mutation in the enzyme phenylalanine hydroxylase, require tyrosine supplementation to support catecholamine production. Since individuals with PKU cannot adequately convert phenylalanine into tyrosine, tyrosine becomes a conditionally essential amino acid for them. This is crucial as tyrosine is a precursor for the synthesis of catecholamines, such as epinephrine and norepinephrine.
A very low protein diet and avoidance of aspartame, which can break down into phenylalanine, are needed to prevent toxic levels of phenylalanine from causing brain damage and other severe health issues.