<prompt> Defect in phenylketonuriaPhenylanine hydroxylaseHomogentisate oxidasePyruvate hydroxylaseFumarylacetoacetate hydroxylase  <response>: In this condition phenylalanine can;t be conveed to tyrosine, so phenylalanine accumulates and it;s level in blood is elevated.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 236, fig 18.1 