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Evidence for synergistic control of glutamate biosynthesis by glutamate dehydrogenases and glutamate in B acillus subtilis
Author(s) -
Stannek Lorena,
Thiele Martin J.,
Ischebeck Till,
Gunka Katrin,
Hammer Elke,
Völker Uwe,
Commichau Fabian M.
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12813
Subject(s) - glutamate dehydrogenase , glutamate synthase , biology , glutamate receptor , biochemistry , glutamine synthetase , biosynthesis , bacillus subtilis , glutamine , enzyme , amino acid , bacteria , genetics , receptor
Summary In the Gram‐positive bacterium, B acillus subtilis glutamate is synthesized by the glutamine synthetase and the glutamate synthase ( GOGAT ). During growth with carbon sources that exert carbon catabolite repression, the rocG glutamate dehydrogenase ( GDH ) gene is repressed and the transcription factor GltC activates the expression of the GOGAT encoding gltAB genes. In the presence of amino acids of the glutamate family, the GDH RocG is synthesized and the enzyme prevents GltC from binding to DNA . The dual control of glutamate biosynthesis allows the efficient utilization of the available nutrients. Here we provide genetic and biochemical evidence that, like RocG , also the paralogous GDH GudB can inhibit the transcription factor GltC , thereby controlling glutamate biosynthesis. Contradictory previous observations show that high level of GDH activity does not result in permanent inhibition of GltC . By controlling the intracellular levels of glutamate through feeding with exogenous arginine, we observed that the GDH ‐dependent control of GltC and thus expression of the gltAB genes inversely correlates with the glutamate pool. These results suggest that the B . subtilis GDHs RocG and GudB in fact act as glutamate sensors. In conclusion, the GDH ‐mediated control of glutamate biosynthesis seems to depend on the intracellular glutamate concentration.