In some organisms, this enzyme is part of a multifunctional protein, together with one or more other components of the system for the biosynthesis of tryptophan [EC 184.108.40.206
(anthranilate phosphoribosyltransferase ), EC 220.127.116.11
(indole-3-glycerol-phosphate synthase), EC 18.104.22.168
(tryptophan synthase) and EC 22.214.171.124
(phosphoribosylanthranilate isomerase)]. The native enzyme in the complex uses either glutamine or, less efficiently, NH3. The enzyme separated from the complex uses NH3 only.