Identification of a suppressor gene for the arginine-auxotrophic argJ mutation in Corynebacterium glutamicum.

We recently proposed a metabolic engineering strategy for L-ornithine production based on the hypothesis that an increased intracellular supply of N-acetylglutamate may further enhance L-ornithine production in a well-defined recombinant strain of Corynebacterium glutamicum. In this work, an argJ-deficient arginine auxotrophic mutant of C. glutamicum is suppressed by a different locus of C. glutamicum ATCC13032. Overexpression of the NCgl1469 open reading frame (ORF), exhibiting N-acetylglutamate synthase (NAGS) activity, was able to complement the C. glutamicum arginine-auxotrophic argJ strain and showed increased NAGS activity from 0.03 to 0.17 units mg(-1) protein. Additionally, overexpression of the NCgl1469 ORF resulted in a 39% increase in excreted L-ornithine. These results indicate that the intracellular supply of N-acetylglutamate is a rate-limiting step during L-ornithine production in C. glutamicum.