The aroF-tyrA operon in E. coli contains two genes that encode proteins involved in chorismate biosynthesis and L-tyrosine biosynthesis respectively. The operon is activated by the redox-sensitive transcriptional activator SoxR, which binds to the promoter region of the operon and when the bacteria is experiencing oxidative stress, it can activate transcription of the operon. The operon can also be repressed by the binding of the transcriptional regulatory protein TyrR. When L-tyrosine levels in the cell are high enough, it can bind to the TyrR protein, forming an active regulatory protein. This can then bind to the promoter region at several different locations, inhibiting transcription of the operon. The first gene in the operon, aroF, encodes a Tyr-sensitive phospho-2-dehydro-3-deoxyheptonate aldolase (DAHP synthase). This enzyme catalyzes the condensation reaction of D-erythrose 4-phosphate (E4P) and phosphoenolpyruvate (PEP) into 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP). This reaction is the first step in the chorismate biosynthesis pathway, an important compound for bacterial biochemical processes. The second gene, tyrA, encodes the T-protein, an enzyme that catalyzees the formation of prephenate from chorismate. This reaction is a part of the L-tyrosine biosynthesis pathway.

Operon: Biosynthesis of Aromatic Amino Acids References