Abstract
3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAHPS) and dehydroquinate synthase (DHQS) are enzymes that catalyze the first and second step of the shikimate pathway. Since the shikimate pathway are absent in mammals, they are potential targets for new antimicrobial agents, anti-parasitic agents and herbicides. DAHPS catalyzes the condensation of phosphoenolpyruvate with erythrose 4-phosphate to give 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP)；DHQS is a NAD-dependent enzyme that converts DAHP into 3-dehydroquinate (DHQ). In this study, we investigated the crystal structure of Helicobacter pylori DAHPS (HpDAHPS) and Mycobacterium tuberculosis DHQS (MtDHQS) as the first step for drug design. The purified HpDAHPS was crystallized and improved diffraction pattern via microseeding screening, additive screening, dehydration and cryprotectant test. Crystallization of MtDHQS, fllowing addition DAHP, gave crystals with 2.07 and 3.00 Å resolution respectively. N-terminal domain has the Rossmann-type architecture, and C-terminal domain contains multipleα-helix structure. MtDHQS in the absence of DAHP, either unliganed or in the presence of NAD+, was an open form；in contrast, DAHP binding turned the MtDHQS into closed form. Structures’ comparison reveals the DAHP binding residues are highly conserved between prokaryotes and eukaryote, which provided a basis for the future structure-guided design of DHQS inhibitors. By using drug IC50 measurement, we try to find out possible inhibitors. The IC50 of drug RH00573 is 64.88 µM.