Mutations in the trpD gene of Corynebacterium glutamicum confer 5- methyltryptophan resistance by encoding a feedback-resistant anthranilate phosphoribosyltransferase

The trpD gene from tryptophan-hyperproducing Corynebacterium glutamicum ATCC 21850 was isolated on the basis of its ability to confer resistance to 5-methyltryptophan on wild-type C. glutamicum AS019. Comparative sequence analysis of the genes from the wild-type AS019 and ATCC 21850 trpD genes revealed two amino acid substitutions at the protein level. Further analysis demonstrated that the trpD gene product from ATCC 21850, anthranilate phosphoribosyltransferase, was more resistant to feedback inhibition by either tryptophan or 5-methyltryptophan than its wild-type counterpart. It is proposed that phosphoribosyltransferase insensitivity to tryptophan in ATCC 21850 contributes to an elevated level of tryptophan biosynthesis.