Question
My son’s hair is very yellow, and I’m worried about a deficiency in trace elements. The doctor said it’s phenylketonuria. What causes phenylketonuria?
Answer
Phenylketonuria is a common amino acid metabolism disorder that occurs due to a defect in phenylalanine and the enzyme, leading to the inability to convert phenylalanine into tyrosine. Phenylalanine and its ketones accumulate in the body and are excreted in large amounts in the urine. This condition is relatively common among genetic amino acid decomposition metabolism defects and is inherited in an autosomal recessive manner. Phenylalanine is one of the amino acids required by the human body; approximately 0.5g of phenylalanine is consumed daily after birth, while children and adults require up to 4g. The conversion of phenylalanine to tyrosine requires not only PAH but also tetrahydrobiopterin (BH4) as a cofactor.