This model represents a bifunctional protein posessing both hisA (1-(5-phosphoribosyl)-5-[(5-phosphoribosylamino)methylideneamino] imidazole-4-carboxamide isomerase) and trpF (N-(5'phosphoribosyl)anthranilate isomerase) activities. Thus, it is involved in both the histidine and tryptophan biosynthetic pathways. Enzymes with this property have been described only in the Actinobacteria (High-GC gram-positive). The enzyme is closely related to the monofunctional HisA proteins (TIGR00007) and in Actinobacteria, the classical monofunctional TrpF is generally absent.
Jiyao W et al.(2023). "The conserved domain database in 2023.",