Question: why does pku cause mental retardation?
Answer: 14.16. 1) deficiency. PAH is a liver-specific enzyme that catalyses the hydroxylation of l-phenylalanine (Phe) to l-tyrosine in the presence of the cofactor, tetrahydrobiopterin. Accumulation of phenylalanine generates a brain damage and consequently irreversible mental retardation.