Enzyme defect in Classic Phenylketonuria
Hyperphenylalaninemias arise from defects in phenylalanine hydroxylase (type I, classic phenylketonuria (PKU), frequency 1 in 10,000 bihs), in dihydrobiopterin reductase (types II and III), or in dihydrobiopterin biosynthesis (types IV and V).Ref: Harper&;s Biochemistry; 30th edition; Chapter 29 Catabolism of the Carbon Skeletons of Amino Acids
Phenylalanine hydroxylase
Dihydrobiopterin reductase
Fumarylacetoacetate hydrolase
Homogentisate oxidase
Metabolism of protein and amino acid