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Ammonia assimilation and glutamate formation in the anaerobe Selenomonas ruminantium.
- Source :
-
Journal of bacteriology [J Bacteriol] 1980 Feb; Vol. 141 (2), pp. 593-602. - Publication Year :
- 1980
-
Abstract
- Selenomonas ruminantium was found to possess two pathways for NH4+ assimilation that resulted in net glutamate synthesis. One pathway fixed NH4+ through the action of an NADPH-linked glutamate dehydrogenase (GDH). Maximal GDH activity required KCl (about 0.48 M), but a variety of monovalent salts could replace KCl. Complete substrate saturation of the enzyme by NH4+ did not occur, and apparent Km values of 6.7 and 23 mM were estimated. Also, an NADH-linked GDH activity was observed but was not stimulated by KCl. Cells grown in media containing non-growth-rate-limiting concentrations of NH4+ had the highest levels of GDH activity. The second pathway fixed NH4+ into the amide of glutamine by an ATP-dependent glutamine synthetase (GS). The GS did not display gamma-glutamyl transferase activity, and no evidence for an adenylylation/deadenylylation control mechanism was detected. GS activity was highest in cells grown under nitrogen limitation. Net glutamate synthesis from glutamine was effected by glutamate synthase activity (GOGAT). The GOGAT activity was reductant dependent, and maximal activity occurred with dithionite-reduced methyl viologen as the source of electrons, although NADPH or NADH could partially replace this artificial donor system. Flavin adenine dinucleotide, flavin mononucleotide, or ferredoxin could not replace methyl viologen. GOGAT activity was maximal in cells grown with NH4+ as sole nitrogen source and decreased in media containing Casamino Acids.
- Subjects :
- Animals
Cell-Free System
Culture Media
Glutamate Dehydrogenase metabolism
Glutamate Synthase metabolism
Glutamate-Ammonia Ligase metabolism
Gram-Negative Anaerobic Bacteria growth & development
Rumen microbiology
Ammonia metabolism
Glutamates biosynthesis
Gram-Negative Anaerobic Bacteria metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9193
- Volume :
- 141
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Journal of bacteriology
- Publication Type :
- Academic Journal
- Accession number :
- 6102549
- Full Text :
- https://doi.org/10.1128/jb.141.2.593-602.1980