Regulation by ammonium and glucose of Arthrobacter fluorescens alanine dehydrogenase |
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Authors: | Isabella Cacciari Daniela Lippi Tito Pietrosanti |
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Institution: | (1) Plant Radiobiochemistry and Ecophysiology Institute, National Research Council, Via Salaria Km. 29,300, I-00016 Monterotondo Scalo, Rome, Italy;(2) Present address: Department of Agrochemistry and Agrobiology, University of Tuscia, Viterbo, Italy |
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Abstract: | Alanine dehydrogenase in Arthrobacter fluorescens exhibited an allosteric behaviour and two K
m values for ammonium were estimated. In batch cultures at different ammonium concentrations and in continuous culture following an NH4
+ pulse, the level of ADH activity seems to be regulated by the ammonium concentration, high activities being observed when extracellular ammonium was in excess. The response to the growth rate of an ammonium-limited chemostat culture of A. fluorescens seems to indicate that alanine dehydrogenase and glutamine synthetase activities were inversely related. High activities of glutamate oxaloacetate transaminase and glutamate pyruvate transaminase have been found in crude extract of ammonium-limited cultures. From the results obtained in batch cultures grown at different glucose concentrations and in carbon-limited chemostat culture it appeared that the limitation by glucose influenced alanine dehydrogenase activity negatively. No glutamate dehydrogenase activity and no glutamate synthase activity could be detected with either NADH or NADPH as coenzymes.Abbreviations ADH
alanine dehydrogenase
- GS
glutamine synthetase
- GDH
glutamate dehydrogenase
- GOGAT
glutamine oxoglutarate aminotransferase
- GOT
glutamate oxaloacetate transaminase
- GPT
glutamate pyruvate transaminase |
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Keywords: | Alanine dehydrogenase Ammonium assimilation Arthrobacter Continuous culture |
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