A soluble Escherichia coli protease has been identified and purified to homogeneity. The protease cleaves glutamine synthetase which has been modified by mixed function oxidation; native glutamine synthetase is not a substrate. Using [14C]glutamine synthetase as a substrate (prepared by growing E. coli on 14C-labeled amino acids), protease activity was assayed by determining the release of tric...

Glutamine synthetase, purified from rat liver, is homogeneous on acrylamide gel electrophoresis and on ultracentrifugation (~20,~) 15.0 S). The enzyme, which consists of eight subunits (subunit molecular weight, 44,000), resembles ovine brain glutamine synthetase in its physical properties, amino acid composition, and substrate specificity. Complete inhibition of the liver enzyme by methionine ...

The level of glutamine synthetase activity in Agmenellum quadruplicatum strain PR-6 was dependent on the nitrogen source used for growth and on the nutritional status of the cells. During exponential growth, glutamine synthetase activity was low in cells grown on ammonia, urea, or nitrate. During the transition from nitrogen replete to nitrogen starved growth, glutamine synthetase activity bega...

An excess of extracellular glutamate in the hippocampus has been linked to the generation of recurrent seizures and brain pathology in patients with medically intractable mesial temporal lobe epilepsy (MTLE). However, the mechanism which results in glutamate excess in MTLE remains unknown. We recently reported that the glutamate-metabolizing enzyme glutamine synthetase is deficient in the hippo...

The structural gene for glutamine synthetase (glnA) in Bacillus subtilis ( glnAB ) cloned in the lambda vector phage Charon 4A was used to transduce a lysogenic glutamine auxotrophic Escherichia coli strain to prototrophy. The defective E. coli gene ( glnAE ) was still present in the transductant since it could be transduced. In addition, curing of the prototroph resulted in the restoration of ...

Glutamine synthetase activity in a cytosol extract of liver was inhibited non-competitively by Mn2+ ions. The apparent Ki for Mn2" in the presence of phosphate was 8 micro M. Inhibition of glutamine synthetase by intracellular Mn2+ may contribute to the very low rates of glutamine synthesis observed in perfused liver and isolated hepatocytes.

The liver shows net glutamine uptake after a protein-containing meal, during uncontrolled diabetes, sepsis and short-term starvation, but changes to net release during long-term starvation and metabolic acidosis. Some studies report a small net release of glutamate by the liver. The differential expression of glutamine synthetase (perivenous) and glutaminase (periportal) within the liver indica...

Ammonia-nitrogen-limited continuous cultures of Escherichia coli and Klebsiella aerogenes contain induced levels of glutamine synthetase that is deadenylyated (i.e., fully active). In the presence of excess ammonia or glutamate in glucose-limited cultures of E. coli, glutamine synthetase is repressed and adenylylated (inactive). The average state of adenylylation (n) is a linear function of the...

The reaction of phenylglyoxal with two enzymes in which ATP plays a complex role has been studied. Both ovine brain glutamine synthetase and Escherichia coli carbamyl phosphate synthetase [carbamoyl-phosphate synthase (glutamine); ATP:carbamate phosphotransferase (dephosphorylating, amido-transferring); EC 2.7.2.9]were inactivated by phenylglyoxal. The specificity of this reagent for arginyl re...

The activity and extent of adenylylation of glutamine synthetase was examined in both free-living and bacteroid forms of Rhizobium japonicum in the presence of excess ammonia. Ammonia caused an apparent repression of glutamine synthetase in free-living R. japonicum and adenylylation of the enzyme was also increased. In contrast, neither the activity nor the extent of adenylylation of the bacter...