Involved in the biosynthesis of the antibiotic phenazine, a nitrogen-containing heterocyclic molecule having important roles in virulence, competition and biological control. Catalyzes the hydrolysis of the vinyl ether functional group of 2-amino-2-deoxyisochorismate (ADIC), yielding pyruvate and trans-2,3-dihydro-3-hydroxyanthranilic acid (DHHA). (2S)-2-amino-4-deoxychorismate + H2O = (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxyate + pyruvate Antibiotic biosynthesis; phenazine biosynthesis. Homodimer. Belongs to the isochorismatase family.