Phenylketonuria is caused by deficiency of: (A) Tyrosine transminase, (B) Tyrosine hydroxylase, (C) Phenylalanine transaminase, (D) Phenylalanine hydroxylase
Answer is D. Deficiency of Phenylalanine hydroxylase is the cause of PKU. The genetic mutation may be in such a way that either the enzyme is not synthesized or a non-functional enzyme is synthesized.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 236