Effects of nitrate, ammonia and glutamate on enzymes of nitrogen assimilation in free living culture of Bradyrhizobium japonicum
1995
Popovic, M. (Faculty of Sciences, Novi Sad (Yugoslavia). Institute of Chemistry) | Saric, M. | Mrkovacki, N. | Milic, V. | Gasic, O.
The effects of nitrate, ammonia and glutamate on the enzymes of nitrogen assimilation and their roles in nitrogen metabolism of some Bradyrhizobium japonicum strains were studied. Glutamine synthetase (GS) and glutamate synthase (GOGAT) exhibited relatively high activities in bacteria cells grown in a medium with ammonia or glutamate. Under the given experimental conditions the NADPH-linked glutamate dehydrogenase (GDH) could be detected only in one strain of Bradyrhizobium japonicum. Activity of nitrate reductase (NR) was significantly increased by the presence of NO3, but was repressed by NH4. The results indicate that the nitrogen assimilation in all investigated strains proceeds exclusively via the GS/GOGAT patway. The only exception, in which GDH was involved in nitrogen metabolism, was a strain exhibiting a low level of this enzyme. Besides, it can be suggested that GS can also be a mechanism-controlling agent in the nitrogen assimilation in Bradyrhizobium japonicum.
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