Active site between two monomers of glutamine synthetase from Salmonella typhimurium. Cation binding sites are yellow and orange; ADP is pink; phosphinothricin is blue.[1]
Glutamine synthetase (GS) (EC 6.3.1.2)[3] is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine:
Glutamine synthetase uses ammonia produced by nitrate reduction, amino acid degradation, and photorespiration.[4] The amide group of glutamate is a nitrogen source for the synthesis of glutamine pathway metabolites.[5]
Other reactions may take place via GS. Competition between ammonium ion and water, their binding affinities, and the concentration of ammonium ion, influences glutamine synthesis and glutamine hydrolysis. Glutamine is formed if an ammonium ion attacks the acyl-phosphate intermediate, while glutamate is remade if water attacks the intermediate.[6][7] Ammonium ion binds more strongly than water to GS due to electrostatic forces between a cation and a negatively charged pocket.[4] Another possible reaction is upon NH2OH binding to GS, rather than NH4+, yields γ-glutamylhydroxamate.[6][7]
^PDB: 1FPY; Gill HS, Eisenberg D (February 2001). "The crystal structure of phosphinothricin in the active site of glutamine synthetase illuminates the mechanism of enzymatic inhibition". Biochemistry. 40 (7): 1903–12. doi:10.1021/bi002438h. PMID 11329256.
^PDB: 2GLS; Yamashita MM, Almassy RJ, Janson CA, Cascio D, Eisenberg D (October 1989). "Refined atomic model of glutamine synthetase at 3.5 A resolution". J. Biol. Chem. 264 (30): 17681–90. doi:10.2210/pdb2gls/pdb. PMID 2572586.
^Eisenberg D, Almassy RJ, Janson CA, Chapman MS, Suh SW, Cascio D, Smith WW (1987). "Some evolutionary relationships of the primary biological catalysts glutamine synthetase and RuBisCO". Cold Spring Harb. Symp. Quant. Biol. 52: 483–90. doi:10.1101/sqb.1987.052.01.055. PMID 2900091.
^ abLiaw SH, Kuo I, Eisenberg D (Nov 1995). "Discovery of the ammonium substrate site on glutamine synthetase, a third cation binding site". Protein Sci. 4 (11): 2358–65. doi:10.1002/pro.5560041114. PMC 2143006. PMID 8563633.
^Liaw SH, Pan C, Eisenberg D (Jun 1993). "Feedback inhibition of fully unadenylylated glutamine synthetase from Salmonella typhimurium by glycine, alanine, and serine". Proc. Natl. Acad. Sci. USA. 90 (11): 4996–5000. Bibcode:1993PNAS...90.4996L. doi:10.1073/pnas.90.11.4996. PMC 46640. PMID 8099447.
^ abLiaw SH, Eisenberg D (Jan 1994). "Structural model for the reaction mechanism of glutamine synthetase, based on five crystal structures of enzyme-substrate complexes". Biochemistry. 33 (3): 675–81. doi:10.1021/bi00169a007. PMID 7904828.
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aspartate. This amidation reaction is similar to that promoted by glutaminesynthetase. The enzyme is ubiquitous in its distribution in mammalian organs...
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Methionine sulfoximine (MSO, also known as MetSox) is an irreversible glutaminesynthetase inhibitor. It is the sulfoximine derivative of methionine with convulsant...
the manganese is bound to manganese metalloproteins, most notably glutaminesynthetase in astrocytes. It is familiar in the laboratory in the form of the...
high as 70%, though some may have a low G+C content. Analysis of glutaminesynthetase sequence has been suggested for phylogenetic analysis of the Actinomycetota...
conserved indels in a number of important proteins, such as Hsp70 and glutaminesynthetase I; but the phylogeny of these genes was interpreted to reveal interdomain...
Regulation of the Glutamine-Dependent Carbamyl Phosphate Synthetase of Escherichia Coli". Mechanism and regulation of the glutamine-dependent carbamyl...
presence of neurotransmitter transporters and the expression of glutaminesynthetase. However, there are distinguishing factors that put SGCs in their...
crucial for the glutamine-dependent activity. In other words, these residues allow CPS III to use glutamine as a substrate. The synthetase subunit stretches...
glutaminase I, L-glutaminase, glutamine aminohydrolase) is an amidohydrolase enzyme that generates glutamate from glutamine. Glutaminase has tissue-specific...
phosphate pathway. In the chloroplasts, glutaminesynthetase incorporates this ammonia as the amide group of glutamine using glutamate as a substrate. Glutamate...
Furthermore, the enzyme glutaminesynthetase (GS) is able to transfer ammonia onto glutamate and synthesize glutamine, replenishing glutamine. The glutamate family...
microbes occurs through the actions of glutamate dehydrogenase and glutaminesynthetase. Glutamate plays the central role in mammalian and microbe nitrogen...
acid corresponding to the codon it recognizes. The enzyme aminoacyl tRNA synthetase "charges" the tRNA molecules with the correct amino acids. The growing...
(cytidine triphosphate) synthetase catalyzes the last committed step in pyrimidine nucleotide biosynthesis: ATP + UTP + glutamine → ADP + Pi + CTP + glutamate...
in the laboratory of Georges Cohen in France and, most notably, glutaminesynthetase, an enzyme that will always be associated with his name. From the...
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