Involved in the third step of the chorismate pathway, which leads to the biosynthesis of aromatic amino acids. Catalyzes the cis-dehydration of 3-dehydroquinate (DHQ) and introduces the first double bond of the aromatic ring to yield 3-dehydroshikimate. The reaction involves the formation of an imine intermediate between the keto group of 3-dehydroquinate and the epsilon-amino group of Lys-170 at the active site. 3-dehydroquinate = 3-dehydroshikimate + H2O kcat is 125 sec(-1) for dehydratase activity with 3-dehydroquinate (at pH 7.5 and 37 degrees Celsius). Metabolic intermediate biosynthesis; chorismate biosynthesis; chorismate from D-erythrose 4-phosphate and phosphoenolpyruvate: step 3/7. Homodimer or homotetramer. Belongs to the type-I 3-dehydroquinase family.