The activities of glutamine synthetase, glutamina aminotransferase, and transglutaminase have been assayed in a number of hepatomas. No correlation exists between any of the enzyme activities and the growth rate, the chromosome number, or the degree of differentiation of the hepatomas. Glutamine synthetase activity declined with successive trans plantations in some hepatoma lines. Adrenalectomy...

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...

Two common ways of measuring the potential for glutamine synthesis in a tissue are the rates of formation of y-glutamylhydroxamate either by synthesis from glutamate (the glutamylhydroxamate synthetase reaction) or by transfer from glutamine (the glutamyltransferase reaction); it has not been established, however, that either reaction is a specific measure of glutamine synthetase. By differenti...

1. Aspergillus nidulans, Neurospora crassa and Escherichia coli were grown on media containing a range of concentrations of nitrate, or ammonia, or urea, or l-glutamate, or l-glutamine as the sole source of nitrogen and the glutamate dehydrogenate and glutamine synthetase of the cells measured. 2. Aspergillus, Neurospora and Escherichia coli cells, grown on l-glutamate or on high concentrations...

Glutamine establishes feedback control of glutamine synthetase (EC 6.3.1.2) in Escherichia coli over a novel loop, viz. by its effect on an enzymatic adenylylation of glutamine synthetase, whose activity is thus modulated. Positive effecters of the adenylyl transfer reaction, magnesium ion and glutamine, increase the number of -SH groups in adenylyltransferase (EC 2.7.7. -) titratable by 5,5’-d...

Twenty-four h after tumor transplantation increases of free glutamine in plasma, liver, and kidney occurred simultaneously with the exponential phase of tumor growth. Kidney and muscle glutamine synthetase also increased in the first 2 days following tumor transplantation, while kidney and liver glutaminases decreased. The levels of free glutamine in plasma and tissues, and the activities of gl...

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...

As the initial aspect of investigations on the regulation of glutamine synthetase in rat hepatomas and in hepatoma cell culture systems, glutamine synthetase from rat liver was purified to apparent homogeneity. A single protein band is found in gels after electrophoresis in three separate systems, and a constant enzyme specific activity is found in fractions containing glutamine synthetase acti...

BACKGROUND/AIMS It has been proposed that, in acute liver failure, skeletal muscle adapts to become the principle organ responsible for removal of blood-borne ammonia by increasing glutamine synthesis, a reaction that is catalyzed by the cytosolic ATP-dependent enzyme glutamine synthetase. To address this issue, glutamine synthetase expression and activities were measured in skeletal muscle of ...

Bacillus subtilis TnrA, a global regulator of transcription, responds to nitrogen availability, but the specific signal to which it responds has been elusive. Genetic studies indicate that glutamine synthetase is required for the regulation of TnrA activity in vivo. We report here that the feedback-inhibited form of glutamine synthetase directly interacts with TnrA and blocks the DNA binding ac...