What is the enzyme mutated in PKU (Phenylketonuria)?

Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase. This enzyme is responsible for converting phenylalanine, an amino acid found in many protein-rich foods, into tyrosine, another amino acid that is important for the production of neurotransmitters and other essential compounds in the body. When phenylalanine hydroxylase is nonfunctional due to a genetic mutation, phenylalanine accumulates to toxic levels, leading to various neurological issues and developmental delays if not managed with dietary restrictions.

The other enzymes listed have different functions and are not directly involved in the metabolism of phenylalanine. Tyrosine hydroxylase is responsible for converting tyrosine to L-DOPA, which is a precursor for dopamine, but it does not handle phenylalanine directly. Hydroxylase reductase is not specifically linked to the metabolism of phenylalanine or its conversion to tyrosine. Similarly, serotonin synthase is involved in the synthesis of serotonin from tryptophan, which is unrelated to PKU. Understanding the role of phenylalanine hydroxylase is crucial in recognizing the biochemical basis of PKU and its clinical management