| | 1 | Author
| Eckhard Bast | Requires cookie* | | | Title
| Ammonia Assimilation by Thiocapsa roseopersicina Grown on Various Nitrogen and Carbon/Electron Sources  | | | | Abstract
| Batch cultures o f the phototrophic bacterium, Thiocapsa roseopersicina, were grown anaero bically in the light either on sulfide with various ammonia concentrations, N 2 or amino acids as nitrogen sources, or on several simple organic substrates in the absence o f reduced sulfur com pounds using 6 mM N H 4C1 as source o f nitrogen. At high ammonia concentrations high activities of (NADPH-linked) glutamate dehydrogenase (GDH), but rather low transferase and no bio synthetic activity of glutamine synthetase (GS) were obtained, while under conditions o f ammonia deficiency (growth with N 2 or glutamate) GDH activity was very low and both GS activities were strongly increased. Glutamate synthase (GOGAT) activity (NADH-dependent) showed little variation. These data indicate that at high NH+ concentrations ammonia is assimilated via GDH, under NHJ limitation, however, via the G S/G O G A T system. Glutamine as nitrogen source may be utilized via GOGAT as well as via an active glutaminase plus GDH. Ammonia, but not glutamine, seems to cause repression and inactivation of GS. Alanine and asparagine inactivate the enzyme inhibiting the biosynthetic, but not the transferase activity. These amino acids in part also influence the activities o f GDH, GOGAT, malate dehydrogenase (MDH) and isocitrate dehydro genase (ICDH). Cultures grown on acetate or pyruvate instead of sulfide showed increased GDH activities and high GS transferase activities possibly reflecting an increase o f intracellular a-ketoglutarate con centration. On malate or fructose also increased GS transferase activities, but rather low GDH activities were observed. High biosynthetic GS activities and elevated GOGAT activities were found only in fructose-grown cells. On the organic substrates the ICDH activities always were somewhat higher than after lithoautotrophic growth. With the exception of acetate, the MDH activities were considerably elevated, especially on pyruvate. The different pathways of ar-keto-glutarate formation and their influence on the enzymes of ammonia assimilation are discussed. | | | |
Reference
| Z. Naturforsch. 35c, 439 (1980); received December 17 1979 | | | |
Published
| 1980 | | | |
Keywords
| Thiocapsa roseopersicina, Phototrophic Bacteria, Nitrogen Sources, Ammonia Assimilation, Carbon Metabolism | | | |
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| default:Reihe_C/35/ZNC-1980-35c-0439.pdf | | | | Identifier
| ZNC-1980-35c-0439 | | | | Volume
| 35 | |
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