The enzyme is composed of two parts, PabA and PabB. In the absence of PabA and glutamine, PabB converts ammonia and chorismate into 4-amino-4-deoxychorismate (in the presence of Mg2+). PabA converts glutamine into glutamate only in the presence of stoichiometric amounts of PabB. This enzyme is coupled with EC?4.1.3.38, aminodeoxychorismate lyase, to form 4-aminobenzoate.
