Kanamori, Keiko and Weiss, Richard L. and Roberts, John D. (1989) Ammonia assimilation pathways in nitrogen-fixing Clostridium kluyverii and Clostridium butyricum. Journal of Bacteriology, 171 (4). pp. 2148-2154. ISSN 0021-9193. http://resolver.caltech.edu/CaltechAUTHORS:KANjbact89
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Pathways of ammonia assimilation into glutamic acid were investigated in ammonia-grown and N2-fixing Clostridium kluyverii and Clostridium butyricum by measuring the specific activities of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. C. kluyverii had NADPH-glutamate dehydrogenase with a Km of 12.0 mM for NH4+. The glutamate dehydrogenase pathway played an important role in ammonia assimilation in ammonia-grown cells but was found to play a minor role relative to that of the glutamine synthetase/NADPH-glutamate synthase pathway in nitrogen-fixing cells when the intracellular NH4+ concentration and the low affinity of the enzyme for NH4+ were taken into account. In C. butyricum grown on glucose-salt medium with ammonia or N2 as the nitrogen source, glutamate dehydrogenase activity was undetectable, and the glutamine synthetase/NADH-glutamate synthase pathway was the predominant pathway of ammonia assimilation. Under these growth conditions, C. butyricum also lacked the activity of glucose-6-phosphate dehydrogenase, which catalyzes the regeneration of NADPH from NADP+. However, high activities of glucose-6-phosphate dehydrogenase as well as of NADPH-glutamate dehydrogenase with a Km of 2.8 mM for NH4+ were present in C. butyricum after growth on complex nitrogen and carbon sources. The ammonia-assimilating pathway of N2-fixing C. butyricum, which differs from that of the previously studied Bacillus polymyxa and Bacillus macerans, is discussed in relation to possible effects of the availability of ATP and of NADPH on ammonia-assimilating pathways.
|Additional Information:||Copyright © 1989 by the American Society for Microbiology. Received 12 September 1988/Accepted 3 January 1989 This work was supported by National Science Foundation grant DMB85-01617. This article is contribution no. 7845 from the Gates and Crellin Laboratories of Chemistry.|
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|Deposited On:||18 Dec 2006|
|Last Modified:||26 Dec 2012 09:24|
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