Figure 2
From: L-glutamine provides acid resistance for Escherichia coli through enzymatic release of ammonia
The glutaminase YbaS is required for Gln-mediated acid resistance in E. coli. (A) The reaction catalyzed by glutaminase results in the release of a molecule of gaseous ammonia. E. coli has two glutaminases, YbaS and YneH, which are thought to function at acidic and neutral/basic pH ranges, respectively. (B) The E. coli glutaminase gene ybaS is required for Gln-mediated acid resistance. Deletion of the glutaminase gene ybaS led to abrogation of acid resistance in the presence of 1 mM Gln. By contrast, deletion of yneH had no effect on acid resistance. (C) Gln-dependent survival of E. coli ΔybaS under acidic environment can be rescued by transformation of a ybaS-expressing plasmid. (D) YbaS exhibits robust glutaminase activity only at pH 6 or lower. By contrast, the glutaminase YneH displays activity only at pH 6 or higher. (E) A summary of the pH-dependent Vmax values of YbaS and YneH. The results shown in panels (B-E) are the average of three independent experiments, with the SDs indicated.
