Carbon source-dependent modulation of NADP-glutamate dehydrogenases in isophthalate-degrading Pseudomonas aeruginosa strain PP4, Pseudomonas strain PPD and Acinetobacter lwoffii strain ISP4.

Acinetobacter lwoffii strain ISP4 metabolizes isophthalate rapidly compared with Pseudomonas aeruginosa strain PP4 and Pseudomonas strain PPD. Isophthalate has been reported to be a potent competitive inhibitor of glutamate dehydrogenase (GDH). Exogenous supplementation of isophthalate with glutamate or alpha-ketoglutarate at 1 mM concentration caused strains PP4 and PPD to grow faster than in the presence of isophthalate alone; however, no such effect was observed in strain ISP4. When grown on isophthalate, all strains showed activity of NADP-dependent GDH (NADP-GDH), while cells grown on glucose, 2x yeast extract-tryptone broth (2YT) or glutamate showed activities of both NAD-dependent GDH (NAD-GDH) and NADP-GDH. Activity staining, inhibition and thermal stability studies indicated the carbon source-dependent presence of two (GDH(I) and GDH(II)), three (GDH(A), GDH(B) and GDH(C)) and one (GDH(P)) forms of NADP-GDH in strains PP4, PPD and ISP4, respectively. The results demonstrate the carbon source-dependent modulation of different forms of NADP-GDH in these bacterial strains. This modulation may help the efficient utilization of isophthalate as a carbon source by overcoming the inhibitory effect on GDH.