<prompt> Phenylketonuria is due to deficiency of:PhenylalaninePhenylalanine hydroxylase PAHGalactokinaseTyrosinase  <response>: Ref. Textbook of Biochemistry for Medical Students. Page.300 Phenylketonuria Defect in Phenyl alanine HydroxylaseA variant, nonclassic PKU, is a result of a defective enzyme in tetrahydrobiopterin synthesis.Mental retardationMusty odor MicrocephalyDiet low in phe nyl-alanineAvoid aspartame Diet important during pregnancy to prevent complication in the kid 