The specific activity of Neurospora crassa glutamine synthetase varies according to the nitrogen source in which the organism is grown. In a poor nitrogen source such as glutamate, the specific activity of the enzyme is higher than that found in good nitrogen sources such as ammonium or glutamine. These differences in specific enzyme activity correspond to differences in enzyme concentration. T...

Helicobacter pylori urease, produced in abundance, is indispensable for the survival of H. pylori in animal hosts. Urea is hydrolyzed by the enzyme, resulting in the liberation of excess ammonia, some of which neutralizes gastric acid. The remaining ammonia is assimilated into protein by glutamine synthetase (EC 6.3.1.2), which catalyzes the reaction: NH3 + glutamate + ATP-->glutamine + ADP + P...

The photosynthetic bacterium Rhodopseudomonas capsulata lacks glutamate dehydrogenase and normally uses the glutamine synthetase/glutamate synthase sequence of reactions for assimilation of N2 and ammonia. The glutamine synthetase in cell-free extracts of the organism is completely sedimented by centrifugation at 140,000 X g for 2 h, is inhibited by L-alanine but not by adenosine 5'-monophospha...

References 1. De Groot CJ, ten Voorde GHJ, van Andel RE, te Kortschot A, Gaasbeek Janzen JW, Wilson RH, et al. Reciprocal regulations of glutamine synthetase and carbamoylphosphate synthetase levels in rat liver. Biochim Biophys Acta 1986;866:61–7. 2. Norenberg MD, Martinez-Hernandez A. Fine structural localization of glutamine synthetase in astrocytes of rat brain. Brain Res 1979;161:303–10. 3...

The use of phosphoenolpyruvate plus pyruvate kinase as an ATP-generating system in the assay for glutamine synthetase activity via the formation of gamma-glutamylhydroxamate from glutamate and hydroxylamine with crude tissue preparations is shown to give values far in excess of the true glutamine synthetase activity of the tissue. This is due to the generation of pyruvate, which reacts with hyd...

1. The activities of the two key enzymes involved in glutamine metabolism, glutaminase and glutamine synthetase, were measured in mucosal biopsies taken from different sites throughout the human gastrointestinal tract, from oesophagus to rectum. 2. The specific activity of glutamine synthetase was highest in the stomach (4.5 nmol glutamine formed per minute per mg of protein), but both small an...

Ammonium assimilation was studied by feeding [15N]ammonium to actively growing mycelium of Agaricus bisporus. Products of ammonium assimilation were analysed using 15N-NMR. Participation of glutamine synthetase, glutamate synthase and NADP-dependent glutamate dehydrogenase was determined by inhibiting glutamine synthetase with phosphinothricin and glutamate synthase with azaserine. Our results ...

Matthias Höpfner , Georg Reifferscheid, and Aloysius Wild Institut für Allgemeine Botanik der Johannes Gutenberg-Universität, Saarstraße 21, D-6500 Mainz, Bundesrepublik Deutschland Z. Naturforsch. 43c, 194-198 (1988); received November 26, 1987 Active Centers, Enzyme Purification, Enzyme Structure, Glufosinate, Glutamine Synthetase, Phosphinothricin Chloroplastic glutamine synthetase of Sinapi...