InterPro domain: IPR012070

Proteins in this entry belong to the prephenate dehydrogenase (PDH) domain superfamily ( PF02153 ). Members of this group catalyse a step in tyrosine biosynthesis in the shikimate pathway, which is present only in bacteria, archaea, fungi, and plants [ 1 ]. Many of the PDH enzymes are able to use the alternative intermediates of tyrosine biosynthesis, prephenate or L-arogenate, as substrates, having both prephenate dehydrogenase and arogenate dehydrogenase activities, and are sometimes collectively called cyclohexadienyl dehydrogenases [ 2 , 3 ]. Arogenate dehydrogenase 2 has a weak prephenate dehydrogenase activity [ 4 ].

Arabidopsis thaliana has two arogenate dehydrogenase isoforms, tyrAAT1 and tyrAAT2. TyrAAT1 is unusual in that it contains a duplication of the PDH domain. Both copies of the PDH domain have arogenate dehydrogenase activity with similar biochemical characteristics [ 5 ]. The experimentally studied plant enzymes are NADP-dependent arogenate dehydrogenases that are very sensitive toward feedback inhibition by the product of the reaction (tyrosine); in fact, they exhibit a higher affinity for tyrosine than for their arogenate substrate [ 5 ]. Interestingly, these proteins do not seem to have any additional domain that can be suggested to be responsible for this regulation.

1. The biosynthesis of shikimate metabolites. FEBS Lett. 18, 334-55
2. A single cyclohexadienyl dehydrogenase specifies the prephenate dehydrogenase and arogenate dehydrogenase components of the dual pathways to L-tyrosine in Pseudomonas aeruginosa. J. Biol. Chem. 265, 20033-6
3. The prephenate dehydrogenase component of the bifunctional T-protein in enteric bacteria can utilize L-arogenate. null 216, 133-9
4. Purification and kinetic analysis of the two recombinant arogenate dehydrogenase isoforms of Arabidopsis thaliana. Eur. J. Biochem. 269, 4753-61