In the absence of functional PAH, phenylalanine cannot be converted into tyrosine. Elevated levels of phenylalanine can inhibit various cellular pathways, including those involved in the synthesis of neurotransmitters such as dopamine and norepinephrine. This can affect neuronal function and lead to intellectual disabilities. Additionally, excess phenylalanine and its byproducts can cause oxidative stress, further damaging cells.
