Catalysis of the reaction: L-glutamine + chorismate = 4-amino-4-deoxychorismate + L-glutamate. It is composed of two enzymatic activities (which may be present on one or two polypeptides); the first is a glutaminase which yields ammonia from glutamine, releasing glutamate. The ammonia is used by the second activity which catalyzes the amination of chorismate to form 4-amino-4-deoxychorismate.