Prephenate dehydratase (EC 4.2.1.51) (PDT) catalyzes the decarboxylation of prephenate into phenylpyruvate. In microorganisms PDT is involved in the terminal pathway of the biosynthesis of phenylalanine. In some bacteria such as Escherichia coli PDT is part of a bifunctional enzyme (P-protein) that also catalyzes the transformation of chorismate into prephenate (chorismate mutase, see <PDOC51167>) while in other prokaryotes it is a monofunctional enzyme [1]. Fungal and plant PDT seem to be monofunctional enzymes as well. Most PDT contain a C-terminal regulatory domain (R), which can be an ACT domain and which allosterically regulates PDT by binding to aromatic amino acids [2,3].

Some proteins known to contain a prephenate dehydratase domain:

• Bacterial P-protein, a bifunctional enzyme composed of two catalytic domains, chorismate mutase and PDT for biosynthesis of phenylalanine (Phe). A C-terminal domain can be involved in feedback inhibition by Phe.
• Mycobacterium tuberculosis PDT encoded by pheA, a monofunctional PDT that is allosterically activated by Phe, Tyr and Trp.
• Yeast prephenate dehydratase.

As signature patterns for PDT we selected two conserved regions. The first region contains a conserved threonine which has been said to be essential for the activity of the enzyme in E. coli [4]. The second motif is located in the regulatory (Phe binding) region in the part C-terminal to PDT and this includes a conserved glutamate. We also developed a profile that covers the entire enzymatic domain of prephenate dehydratase.