In phenylketonuria, the mutation affects which enzyme?

Phenylalanine hydroxylase

The correct answer is Option (2)- Phenylalanine hydroxylase

Phenylketonuria : This inborn error of metabolism is also inherited as the autosomal recessive trait. The disease is caused by mutation in the gene that codes for the enzyme phenyl alanine hydroxylase (single gene mutation).The affected individual lacks an enzyme that converts the amino acid phenylalanine into tyrosine. As a result of this phenylalanine is accumulated and converted into phenylpyruvic acid and other derivatives. Accumulation of these in brain results in mental retardation. These are also excreted through urine because of its poor absorption by kidney.