<p>This entry represents a bifunctional protein possessing both hisA (1-(5-phosphoribosyl)-5-[(5-phosphoribosylamino)methylideneamino] imidazole-4-carboxamide isomerase) and trpF (N-(5'phosphoribosyl)anthranilate isomerase) activities [<cite idref="PUB00013823"/>]. 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 and in Actinobacteria, the classical monofunctional TrpF is generally absent.</p>