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Glutamate biosynthesis in Bacillus azotofixans. 15N NMR and enzymatic studies

Kanamori, Keiko and Weiss, Richard L. and Roberts, John D. (1988) Glutamate biosynthesis in Bacillus azotofixans. 15N NMR and enzymatic studies. Journal of Biological Chemistry, 263 (6). pp. 2817-2823. ISSN 0021-9258.

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Pathways of ammonia assimilation into glutamic acid in Bacillus azotofixans, a recently characterized nitrogen-fixing species of Bacillus, were investigated through observation by NMR spectroscopy of in vivo incorporation of 15N into glutamine and glutamic acid in the absence and presence of inhibitors of ammonia-assimilating enzymes, in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthase, and alanine dehydrogenase. In ammonia-grown cells, both the glutamine synthetase/glutamate synthase and the glutamate dehydrogenase pathways contribute to the assimilation of ammonia into glutamic acid. In nitrate-grown and nitrogen-fixing cells, the glutamine synthetase/glutamate synthase pathway was found to be predominant. NADPH-dependent glutamate dehydrogenase activity was detectable at low levels only in ammonia-grown and glutamate-grown cells. Thus, B. azotofixans differs from Bacillus polymyxa and Bacillus macerans, but resembles other N2-fixing prokaryotes studied previously, as to the pathway of ammonia assimilation during ammonia limitation. Implications of the results for an emerging pattern of ammonia assimilation by alternative pathways among nitrogen-fixing prokaryotes are discussed, as well as the utility of 15N NMR for measuring in vivo glutamate synthase activity in the cell.

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Additional Information:Copyright © 1988 by the American Society for Biochemistry and Molecular Biology. (Received for publication, August 27, 1987) We would like to thank Dr. Francis Martin for helpful discussion and careful reading of the manuscript. This work was supported by National Science Foundation Grant DMB85-01617 and is Contribution 7645 from the Gates and Crellin Laboratories of the California Institute of Technology. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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Caltech Gates and Crellin Laboratories of Chemistry7645
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Deposited On:19 Dec 2006
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