Medically reviewed by Aviv Joshua, MS, RDN Phenylalanine is an essential amino acid (building block of protein) that the body ...

Phenylalanine is metabolized to produce maleylacetoacetate in a four-step biochemical reaction. Absence of the enzyme homogentisate oxidase causes the buildup of homogentisate, leading to the ...

Once a child was diagnosed, a strict low-phenylalanine diet could prevent further damage, but Warner had no easy way to measure phenylalanine levels in his PKU patients’ blood to monitor the diet’s ...