Bifunctional enzyme that catalyzes the biosynthesis of 4-amino-4-deoxychorismate (ADC) from chorismate and glutamine. In the first step, a glutamine amidotransferase generates ammonia that is channelled between the binding sites of glutamine and chorismate and used along with chorismate in the second step, catalyzed by aminodeoxychorismate synthase, to produce ADC. Required for the synthesis of 4-aminobenzoate (PABA), an important component in tetrahydrofolate biosynthesis. Does not possess ADC lyase activity (By similarity). chorismate + L-glutamine = 4-amino-4-deoxychorismate + L-glutamate Cofactor biosynthesis; tetrahydrofolate biosynthesis; 4-aminobenzoate from chorismate: step 1/2. Antibiotic biosynthesis; candicidin biosynthesis. The PABA component provides the glutamine amidotransferase activity. The PABB component catalyzes the formation of ADC by binding chorismate and ammonia. In the C-terminal section; belongs to the anthranilate synthase component I family.