Most hepatomas contain only traces of glutamine synthetase (GS) although they originate from liver which has high levels of the enzyme (1-3) The H T C cell line which was derived from Morris Hepa toma 7288C retained certain characteristics of liver cells, notably the induction of tyrosine amino transferase (4, 5), while other liver characteristics, among them GS activity, could not be detected ...

Glutamine is an important renal glucose precursor and energy provider. In order to advance our understanding of the underlying metabolic processes, we studied the metabolism of variously labelled [13C]glutamine and [14C]glutamine molecules and the effects of fasting in isolated rat renal proximal tubules. Absolute fluxes through the enzymes involved, including enzymes of four different cycles o...

Growth of a glutamine synthetase-deficient mutant of Streptococcus thermophilus was compared to that of the parent strain in milk that was not supplemented or was supplemented with ammonium chloride, glutamine, or the urease inhibitor flurofamide. It was concluded that one of the functions of urease is to supply ammonia for the synthesis of glutamine.

In this investigation, the effect of bialaphos (phosphinothricyl-alanyl-alanine) on the enzymes involved in NH4+-assimilation — glutamine synthetase, glutamine-2-oxoglutarate aminotrans­ ferase, glutamate dehydrogenase — is examined and compared to the effect of phosphinothricin (glufosinate) on the same enzymes. Bialaphos was given to whole plants (in vivo) and to leaf homogenate (in vitro). T...

Nicotinamide adenine dinucleotide phosphate (reduced form)-nitrate reductase was freed from ammonium repression in a Neurospora crassa mutant having drastically lowered glutamine synthetase activity, gln-1a. The general phenomenon of nitrogen metabolite repression required glutamine or some aspect of glutamine metabolism.

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...

The a-methyl and a-ethyl analogs of methionine sulfoximine, like methionine sulfoximine, induce convulsions in mice and inhibit glutamine synthetase irreversibly; cu-ethylmethionine sulfoximine is approximately 50% as inhibitory as methionine sulfoximine and a-methylmethionine sulfoximine. However, whereas cy-methylmethionine sulfoximine and methionine sulfoximine inhibit y-glutamylcysteine syn...

Asparagine synthetase B catalyzes the assembly of asparagine from aspartate, Mg(2+)ATP, and glutamine. Here, we describe the three-dimensional structure of the enzyme from Escherichia colidetermined and refined to 2.0 A resolution. Protein employed for this study was that of a site-directed mutant protein, Cys1Ala. Large crystals were grown in the presence of both glutamine and AMP. Each subuni...

Glutamine synthetase (EC 6.3.1.2) catalyses the formation of glutamine from glutamate and ammonia coupled with the breakdown of ATP to ADP and phosphate. In the presence of ATP, glutamate and Mg, but in the absence of ammonia the enzyme forms a complex containing glutamate, ADP and phosphate; with ammonia, this complex forms glutamine, ADP, phosphate and free enzyme. The presence of ATP is nece...