Can function as either prephenate dehydrogenase or as arogenate dehydrogenase in the biosynthesis of L-tyrosine. Catalyzes two analogous reactions: converts prephenate to 4-hydroxyphenylpyruvate and transforms L-arogenate to L-tyrosine. Is not able to utilize NADP(+) instead of NAD(+) as cosubstrate. L-arogenate + NAD(+) = CO2 + L-tyrosine + NADH NAD(+) + prephenate = 3-(4-hydroxyphenyl)pyruvate + CO2 + NADH Insensitive to feedback inhibition by L-tyrosine. The KM value obtained for NAD(+) is the same regardless of whether the enzyme is assayed as arogenate dehydrogenase or as prephenate dehydrogenase. Has a greater Vmax with L-arogenate as substrate (about 3-fold higher than with prephenate). Optimum pH is 6.6 for both activities. Amino-acid biosynthesis; L-tyrosine biosynthesis; (4-hydroxyphenyl)pyruvate from prephenate (NAD(+) route): step 1/1. Amino-acid biosynthesis; L-tyrosine biosynthesis; L-tyrosine from L-arogenate (NAD(+) route): step 1/1. Homodimer. Belongs to the prephenate/arogenate dehydrogenase family.