Converts the prephenate produced from the shikimate-chorismate pathway into phenylalanine (PubMed:17726025). Dehydratase that uses arogenate and prephenate as substrates (PubMed:17726025). Utilzes more efficiently arogenate than prephenate (PubMed:17726025). H(+) + L-arogenate = CO2 + H2O + L-phenylalanine H(+) + prephenate = 3-phenylpyruvate + CO2 + H2O Amino-acid biosynthesis; L-phenylalanine biosynthesis; L-phenylalanine from L-arogenate: step 1/1. Amino-acid biosynthesis; L-phenylalanine biosynthesis; phenylpyruvate from prephenate: step 1/1. Expressed in roots, leaves, stems, flowers and siliques.