What is the primary amino acid deficiency in PKU?

In Phenylketonuria (PKU), the primary amino acid deficiency is in tyrosine. PKU is a genetic disorder that results from a deficiency in the enzyme phenylalanine hydroxylase (PAH), which is responsible for converting phenylalanine to tyrosine. When this enzyme is deficient or absent, phenylalanine accumulates in the body and leads to toxic effects, while tyrosine, which is synthesized from phenylalanine, becomes deficient.

Tyrosine plays a crucial role in the production of important substances in the body, including neurotransmitters like dopamine and hormones like epinephrine. The lack of tyrosine in individuals with PKU can lead to various neurological deficits and other complications.

The other amino acids mentioned, including leucine, isoleucine, and valine, are not primarily affected in PKU. Leucine, isoleucine, and valine are branched-chain amino acids that have different metabolic pathways and are not directly linked to the enzymatic defect seen in PKU. Therefore, while there may be multiple amino acids in the diet, the specific deficiency of tyrosine due to the lack of conversion from phenylalanine is central to