A method for producing vectors containing a gene coding for an enzyme having reduced or deactivated feedback inhibition and to the use thereof for producing amino acids and nucleotide. Genes coding for feedback-inhibited enzymes are mutagenized in vitro, —ligated into vectors in a further step—the vectors are each transformed in a microorganism containing a metabolite sensor in a further step, which brings about the synthesis of a fluorescent protein at an increased metabolite concentration, —whereupon microorganisms exhibiting increased or maximum fluorescence are selected; and —the vectors that contain a gene coding for an enzyme having reduced or deactivated feedback inhibition are isolated from microorganisms having increased or maximum fluorescence.