Glutamine synthetase (GS) utilizes various substituted glutamic acids as substrates. We have used this information to design herbicidal alpha- and gamma-substituted analogs of phosphinothricin (l-2-amino-4-(hydroxymethylphosphinyl)butanoic acid, PPT), a naturally occurring GS inhibitor and a potent herbicide. The substituted phosphinothricins inhibit cytosolic sorghum GS(1) and chloroplastic GS...

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...

Glutamine synthetase is a ubiquitous central enzyme in nitrogen metabolism that is controlled by up to four regulatory mechanisms, including adenylylation of some or all of the twelve subunits by adenylyl transferase. It is considered a potential therapeutic target for the treatment of tuberculosis, being essential for the growth of Mycobacterium tuberculosis, and is found extracellularly only ...

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...

Pseudomonas syringae pv. tabaci, a commonly recognized leaf pathogen of tobacco, can infest the rhizosphere of many plants, including oats. Normal oat plants do not survive this infestation as a consequence of the complete and irreversible inactivation of all of their glutamine synthetases by tabtoxinine-beta-lactam (TbetaL), a toxin released by pv. tabaci. We have identified a population of oa...

Renal glutamine synthetase catalyzes the reaction of NH4+ with glutamate, forming glutamine and decreasing the ammonia available for net acid excretion. The purpose of the present study was to determine glutamine synthetase's specific cellular expression in the mouse kidney and its regulation by hypokalemia, a common cause of altered renal ammonia metabolism. Glutamine synthetase mRNA and prote...

The formation of y-glutamylhydroxamate by homogenates under optimum assay condition showed an inconstancy in the ratios of the enzyme activities utilizing L-glutamate and ATP (y-glutamylhydroxamate synthetase) and L-glutamine and ADP (L-glutaminehydroxylamine glutamyltransferase) in a number of normal and neoplastic rat tissues. Although y-glutamylhydroxamate synthetase activities in adult live...

Astrocytes are claimed to protect neurons against excitotoxicity by clearing glutamate from the extracellular space and rapidly converting it into glutamine. Glutamine, is then released into the extracellular medium, taken up by neurons and transformed back into glutamate which is then stored into synaptic vesicles. Glutamine synthetase (GS), the key enzyme that governs this glutamate/glutamine...

The change in glutamine synthetase activity has been studied under two conditions of liver growth, namely, mitotic growth after partial hepatectomy and nonmitotic growth during repletion after a fast. The surgical operation caused the enzyme activity in the liver to diminish to one half its normal value within one week after the operation and to remain at this reduced level for the duration of ...

The arginase tissue distribution, the biochemical properties of the argininolytic system and the subcellular localization of the enzymes carbamoylphosphate synthetase, ornithinecarbamoyl transferase, glutamine synthetase and arginase in Antarctic fish, N. neglecta and N. rossii were the main aims of the present work. The tissue with highest argininolytic activity was the kidney distal portion a...