Glutamate 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 ... 

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

This enzyme [EC 6.3.2.17], which is also known as folyl-poly-y-glutamate synthetase, catalyzes the sequential ATP-dependent addition of glutamyl groups onto tetra-hydrofolyl-[Glu] to yield tetrahydrofolyl-[Glu] +i plus ADP and orthophosphate. 

Glutamate synthetase, which is not present in humans but is found in bacteria, catalyzes the formation of glutamate ... 

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

Glutamate synthetase activity was determined by following glutamate formation. The reaction mixture contained in a final volume of 0.9 mL 45 //mol potassium phosphate buffer (pH 7.0), 5 /u.mol L-glutamine, 1 //mol 2-oxoglutarate, 5 //mol aminooxyacetate, 10 nmol Synechococcus ferredoxin, and enzyme. The reaction was started by adding 0.8 mg of sodium dithionite freshly dissolved in 0.1 mL of 0.12 M NaHCO and stopped after 15 minutes at 30°C by the addition of 0.6 mL of 1 N HQ. 

Figure 9.41 Chromatograms of enzyme assay media. (A) Elution profile of the assay medium of glutamine synthetase. Alder root nodule enzyme plus assay mixture was incubated for IS minutes. (B) Elution profile of the assay medium of glutamate synthetase. Rice leaves enzyme plus assay mixture was incubated for 15 minutes. (From Martin et al., 1982.)...

Cichowicz DJ and Shane B (1987) Mammalian folylpoly-gamma-glutamate synthetase. 2. Substrate specificity and kinetic properties. Biochemistry 26, 513-21. 

Avda, C., BoteUa, J. R., Canovas, F. M., Castro, I. N., and Valpuesta, V. (1987). Different characteristics of the two glutamate synthetases in the green leaves of Lycopersicon esculentum. Plant Physiol. 85, 1036-1039. 

As a congenital disorder, an enzyme deficiency in the urea cycle relates to carbamoylphosphate synthetase or N-ace-tyl-glutamate synthetase (= hyperammonaemia type I) and ornithine carbamoyltransferase (= hyperammonaemia type II) (D.B. Flannery et al., 1982). (27) (s. p. 594) This condition mainly affects the channelling of ammonium into the mitochondria and the conversion of ornithine into citrulline. (s. fig. 3.12) Similar acquired enzymopathies can be expected in Reye s syndrome and in cases of zinc deficiency. Such a hyperammonaemia syndrome can also produce the clinical picture of HE. 

In contrast to cyanophycin, the biosynthesis of poly-y-glutamate appears to involve a coupled system composed of various enzymes [61]. In vitro synthesis of poly-y-glutamate via isolated enzymes has not been reported. An article has been published on the isolation of folylpoly-a-glutamate synthetase and its in vitro reaction to add glutamate residues to polyglutamate substrates via a-COOH linkages [62]. 

With both DHFR selection and the glutamate synthetase (GS) system, expression of both the selection gene and the gene of interest can be augmented by exposing recombinant cells to drugs that block the ac-... 

Figure 12-4. Gamma-aminobutyric acid metabolic interactions. GA = glutaminase GABA = y-aminobutyric acid GABA-T = GABA a-oxaloglutarate transaminase GAD = glutamic acid decarboxylase GS = glutamic synthetase NAD+ = nicotinamide adenine dinucleotide PP = pyridoxal phosphate (vitamin B6) SSA = succinic semialdehyde SSADH = succinic semialdehyde dehydrogenase GHB = y-hydroxybutyric acid GBL = y-butyrolactone.

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