Structural and Biochemical Analysis of 3-Dehydroquinate Dehydratase from .

Dehydroquinate dehydratase (DHQD) catalyzes the conversion of 3-dehydroquinic acid (DHQ) into 3-dehydroshikimic acid in the mid stage of the shikimate pathway, which is essential for the biosynthesis of aromatic amino acids and folates. Here, we report two the crystal structures of type II DHQD (DHQD) derived from , which is a widely used industrial platform organism. We determined the structures for DHQD with the citrate at a resolution of 1.80Å and DHQD with DHQ complexed forms at a resolution of 2.00 Å, respectively. The enzyme forms a homododecamer consisting of four trimers with three interfacial active sites. We identified the DHQ-binding site of DHQD and observed an unusual binding mode of citrate inhibitor in the site with a half-opened lid loop. A structural comparison of DHQD with a homolog derived from revealed differences in the terminal regions, lid loop, and active site. Particularly, DHQD, including some species, possesses a distinctive residue P105, which is not conserved in other DHQDs at the position near the 5-hydroxyl group of DHQ. Replacements of P105 with isoleucine and valine, conserved in other DHQDs, caused an approximately 70% decrease in the activity, but replacement of S103 with threonine (DHQD) caused a 10% increase in the activity. Our biochemical studies revealed the importance of key residues and enzyme kinetics for wild type and DHQD, explaining the effect of the variation. This structural and biochemical study provides valuable information for understanding the reaction efficiency that varies due to structural differences caused by the unique sequences of DHQD.