<prompt> Type I phenylketonuria is caused by a deficiency ofPhenylalanine transminasePhenylalanine hydrolaxaseTyrosine transaminaseTyrosine hydroxylase  <response>: Hyperphenylalaninemias arise from defects in phenylalanine hydroxylase, EC 1.14.16.1 type I, classic phenylketonuria PKU, frequency 1 in 10,000 bihs, in dihydrobiopterin reductase types II and III, or in dihydrobiopterin biosynthesis types IV and V.Ref: Harper;s Biochemistry; 30th edition; Chapter 29 Catabolism of the Carbon Skeletons of Amino Acids 