May catalyze the conversion of 3,4-dideoxy-4-amino-D-arabino-heptulosonate 7-phosphate (aDAHP) to 5-deoxy-5-amino-3-dehydroquinate (aDHQ). Probably involved in the formation of 3-amino-5-hydroxybenzoic acid (AHBA), the precursor of rifamycin and related ansamycins. Inactivation of the gene does not affect rifamycin production significantly. Belongs to the sugar phosphate cyclases superfamily. aDHQS family.