Phenylalanemia I is due to deficiency of ?

Phenylalanine hydroxylase i) Classical phenylketonuria (hyperphenylalanemia type I) Deficiency of phenylalanine hydroxylase.ii) Atypical phenylketonuria (hyperphenylalanemia type II and III) * Defect in dihydrobiopterin reductase.iii) Hyperphenylalanemia type IV and V * Defect in dihydrobiopterin synthesis.