Catalytic domain of prephenate dehydratase and similar proteins; the type 2 periplasmic binding protein fold
Prephenate dehydratase (PDT, EC:4.2.1.51) converts prephenate to phenylpyruvate through dehydration and decarboxylation reactions. PDT plays a key role in the biosynthesis of L-Phe in organisms that utilize the shikimate pathway. PDT is allosterically regulated by L-Phe and other amino acids. The catalytic PDT domain consists of two similar subdomains with a cleft in between, which hosts the highly conserved active site. In gram-postive bacteria and archaea, PDT is a monofunctional enzyme, consisting of a catalytic domain (PDT domain) and a regulatory domain (ACT) (aspartokinase, chorismate mustase domain). In gram-negative bacteria, PDT exists as fusion protein with chorismate mutase (CM), forming a bifunctional enzyme, P-protein (PheA). The CM in the P-protein catalyzes the pericycle isomerization of chorismate to prephenate that serves as a substrate for PDT. The CM and PDT are essentail enzymes for the biosynthesis of aromatic amino acids in microorganisms but are not found in humans. Thus, both CM and PDT can potentially serve as drug targets against microbial pathogens. The PDT domain has the same structural fold as the type 2 periplasmic binding proteins (PBP2), many of which are involved in chemotaxis and uptake of nutrients and other small molecules from the extracellular space as a primary receptor. The PBP2 proteins are typically comprised of two globular subdomains connected by a flexible hinge and bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap.
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