Answer:
Feedback inhibition may be defined as the biological mechanism that are mainly formed for the inhibition of the preformed enzymes. Two main types of regulation are positive regulation and negative regulation.
The feedback regulation shown by E.coli for the tryptophan biosynthesis is the negative inhibition. This means that the operon is being involved in switching off by bounding to the active form of the repressor protein. The positive regulation occurs when the regulatory protein interacts with the genome.