Conversion of phenylalanine to tyrosine is hampered in ?

Ans. is 'a' i.e., PhenylketonuriaPhenylketonuria is characterized by inability of oxidation of phenylalanine into tyrosine.It is an inborn metabolism of phenylalanine, in which there is inability of oxidation of phenylalanine into tyrosine. There is defective function of phenylalanine hydroxylase, which may be due to : ?Classical phenylketonuria (hyperphenylalanemia type I) - Deficiency of phenylalanine hydroxylase.Atypical phenylketonuria (Hyperphenylalanemia type II and III) - Defect in dihydrobiopterin reductase.Hyperphenylalanemia type - IV and V - Defect in dihydrobiopterin synthesis.