Synthetases glutamate synthetase

Glutamine Synthetase, Glutamate Synthetase, and Glutamate Dehydrogenase (Martin et al., 1982 Marques et al., 1989)... 

In E. coli GTP cyclohydrolase catalyzes the conversion of GTP (33) into 7,8-dihydroneoptetin triphosphate (34) via a three-step sequence. Hydrolysis of the triphosphate group of (34) is achieved by a nonspecific pyrophosphatase to afford dihydroneopterin (35) (65). The free alcohol (36) is obtained by the removal of residual phosphate by an unknown phosphomonoesterase. The dihydroneoptetin undergoes a retro-aldol reaction with the elimination of a hydroxy acetaldehyde moiety. Addition of a pyrophosphate group affords hydroxymethyl-7,8-dihydroptetin pyrophosphate (37). Dihydropteroate synthase catalyzes the condensation of hydroxymethyl-7,8-dihydropteroate pyrophosphate with PABA to furnish 7,8-dihydropteroate (38). Finally, L-glutamic acid is condensed with 7,8-dihydropteroate in the presence of dihydrofolate synthetase. 

Ammonia is accepted by glutamic acid in an energy (ATP consuming) step, and converted to glutamine. This reaction is catalysed by glutamate synthetase (GS) and can be written as ... 

The enzymes glutamate dehydrogenase, glutamine synthetase, and aminotransferases occupy central positions in amino acid biosynthesis. The combined effect of... 

S. E. Smith, B. L. St John, F. A. Smith, and D. j. D. Nicholas, Activity of glutamine synthetase and glutamate dehydrogenase in Trifolium subterraneum and Allium cepa L., effects of mycorrhizal infection and phosphorus nutrition. New Phytologist 99 211 (1985). 

Such enzymes catalyse the condensation of specific compounds, accompanied by the breakdown of a pyrophosphate bond in adenosine triphosphate (10.64). Adenosine is the condensation product of a pentose (D-ribofuranose) and a purine (adenine). Scheme 10.15 shows the action of glutamine synthetase on a mixture of L-glutamic acid (10.65) and... 

Iida T., Kawabe T., Noguchi F., Mitamura T., Nagata K., Tomita K., ISFET-type -glutamate sensor using thermophilic glutamine-synthetase from a thermophile, Nippon-Kagaku-Kaishi 1987 10 1817-1821. 

In earlier studies the in vitro transition metal-catalyzed oxidation of proteins and the interaction of proteins with free radicals have been studied. In 1983, Levine [1] showed that the oxidative inactivation of enzymes and the oxidative modification of proteins resulted in the formation of protein carbonyl derivatives. These derivatives easily react with dinitrophenyl-hydrazine (DNPH) to form protein hydrazones, which were used for the detection of protein carbonyl content. Using this method and spin-trapping with PBN, it has been demonstrated [2,3] that protein oxidation and inactivation of glutamine synthetase (a key enzyme in the regulation of amino acid metabolism and the brain L-glutamate and y-aminobutyric acid levels) were sharply enhanced during ischemia- and reperfusion-induced injury in gerbil brain. 

V-acetylglutamate synthetase deficiency. A deficiency of CPS also can arise because of the congenital absence of NAG synthetase, which catalyzes the formation of NAG from glutamate and acetyl-CoA. NAG is an obligatory effector of CPS. The few patients reported have had a malignant course of neonatal onset. 

The cycle is renewed after the cysteine formed in reaction 6 and the glutamate derived from reaction 6 are converted to y-glutamylcysteine via y-glutamylcysteine synthetase (reaction 1). 

Glutamine synthetase, a brain Mn enzyme, is located mainly in astrocytes, and its synthesis may be modulated by nitric oxide (496). Inhibition of this enzyme could be relevant to aging diseases (497). There is evidence that human NT2-N neurons die via ionotropic glutamate receptor-mediated mechanisms when exposed to hypoxia in the presence of glutamate (498). 

Glutamine synthetase 6.3.1.2 C L-Glutamate NADH ADP Pyruvate Pyruvate kinase Lactate dehydrogenase... 

L-Glutamate synthetase 6.3.1.2 L-Glutamate/ATP Phosphate Determination of phosphate... 

Glutathione, which is synthesized by two ATP molecules requiring synthetase enzymes (y glutamate cysteine synthetase and glutathione synthetase), is present at a concentration of about 2 mM in a red cell. To be an effective redox buffer , the ratio of GSH to GSSG must be kept high. This is achieved by the reduction of GSH by NADPH and glutathione reductase ... 

L-Glutamate, glutamine synthetase intermediate, 28 356, 361, 365 Glutamine synthetase, 28 349-366 active site, 28 350... 

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