Question

How can high levels of amino acids can act as feedback inhibitors?

Answer 1

High levels of amino acids such as Tryptophan [Trp], can bind to proteins known as repressors and then attach to a region/sequence on the gene called the operator. The attachment of such a complex on the operator dictates whether the genes downstream of the operator will be transcribed or not. This is because the translation machinery which assembles at the promoter site still needs to make its way to the genes of interest, namely trpE to trpA.
Such genetic constructs ar referred to as operons.