If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: glutamine biosynthesis (nitrogen remobilization from senescing leaves)
|Superclasses:||Biosynthesis → Amino Acids Biosynthesis → Individual Amino Acids Biosynthesis → Glutamine Biosynthesis|
Some taxa known to possess this pathway include : Arabidopsis thaliana col
Expected Taxonomic Range: Embryophyta
In plants, the protein levels in seeds influence seed survival in natural settings and help determine the seeds' nutritional value and processing properties when they are grown for human and animal consumption. A large fraction of this protein content may be derived from the remobilization of nitrogen from proteins in senescing leaves [Hirel01, Barneix07, Donnison07]. This nitrogen can be transported in the form of amino acids, prinicipally glutamine, through the phloem. Improving the efficiency of this process could lead to the production of seed-based crops with higher protein levels [Taylor10].
One of the enzymes in this pathway, pyruvate, orthodiphosphate dikinase (PPDK), plays a prominent role in photosynthesis in C4 plants such as Zea mays (maize), yet it is also expressed in C3 plants, such as Arabidopsis thaliana col. This pathway may help to explain the physiological function of PPDK in C3 plants [Taylor10]. Interestingly, in all plant species studied to date, both a cytosolic and a chloroplastic isoform of the PPDK enzyme are generated from alternative promoters upstream of the same chromosomal locus. Over-expression of the cytosolic form of this enzyme in Arabidopsis during senescence can lead to an increase in seed weight and seed nitrogen content indicating that this form of the enzyme may be important for nitrogen remobilization [Taylor10].
About This Pathway
Portions of this pathway likely occurs in several subcellular compartments, notably, the cytosol, mitochondria, and chloroplast. The pyruvate that initally feeds into this pathway may be derived from the deamination of some amino acids, such as threonine, glycine, serine, alanine, and cysteine.
Starting with pyruvate, after the sequential activities of cytosolic PPDK and PEP carboxylase, the oxaloacetate (OAA) produced can flow into the TCA cycle in the mitochondria where it can be converted to citrate. The citrate may be metabolized in the mitochondria or the cytosol by aconitase. The subsequent transformation of isocitrate into 2-oxoglutarate can be catalyzed by NAD+-dependent isocitrate dehydrogenase in the mitochondria [Lemaitre06] or by NADP+-dependent isocitrate dehydrogenase in the cytosol [Mhamdi10, Taylor10].
In the chloroplast, this 2-oxoglutarate carbon skeleton can then be transformed into a nitrogen-transporting amino acid by the activities of glutamate synthase and glutamine synthase. The resulting L-glutamine can then be exported to seeds through the phloem [Taylor10].
Donnison07: Donnison IS, Gay AP, Thomas H, Edwards KJ, Edwards D, James CL, Thomas AM, Ougham HJ (2007). "Modification of nitrogen remobilization, grain fill and leaf senescence in maize (Zea mays) by transposon insertional mutagenesis in a protease gene." New Phytol 173(3);481-94. PMID: 17244043
Hirel01: Hirel B, Bertin P, Quillere I, Bourdoncle W, Attagnant C, Dellay C, Gouy A, Cadiou S, Retailliau C, Falque M, Gallais A (2001). "Towards a better understanding of the genetic and physiological basis for nitrogen use efficiency in maize." Plant Physiol 125(3);1258-70. PMID: 11244107
Lemaitre06: Lemaitre T, Hodges M (2006). "Expression analysis of Arabidopsis thaliana NAD-dependent isocitrate dehydrogenase genes shows the presence of a functional subunit that is mainly expressed in the pollen and absent from vegetative organs." Plant Cell Physiol 47(5);634-43. PMID: 16527867
Mhamdi10: Mhamdi A, Mauve C, Gouia H, Saindrenan P, Hodges M, Noctor G (2010). "Cytosolic NADP-dependent isocitrate dehydrogenase contributes to redox homeostasis and the regulation of pathogen responses in Arabidopsis leaves." Plant Cell Environ 33(7);1112-23. PMID: 20199623
Taylor10: Taylor L, Nunes-Nesi A, Parsley K, Leiss A, Leach G, Coates S, Wingler A, Fernie AR, Hibberd JM (2010). "Cytosolic pyruvate,orthophosphate dikinase functions in nitrogen remobilization during leaf senescence and limits individual seed growth and nitrogen content." Plant J 62(4);641-52. PMID: 20202167
Alibhai94: Alibhai M, Villafranca JJ (1994). "Kinetic and mutagenic studies of the role of the active site residues Asp-50 and Glu-327 of Escherichia coli glutamine synthetase." Biochemistry 33(3);682-6. PMID: 7904829
Amaya05: Amaya KR, Kocherginskaya SA, Mackie RI, Cann IK (2005). "Biochemical and mutational analysis of glutamine synthetase type III from the rumen anaerobe Ruminococcus albus 8." J Bacteriol 187(21);7481-91. PMID: 16237031
Anderson88: Anderson DH, Duckworth HW (1988). "In vitro mutagenesis of Escherichia coli citrate synthase to clarify the locations of ligand binding sites." J Biol Chem 1988;263(5);2163-9. PMID: 3276685
Balakrishnan78: Balakrishnan MS, Villafranca JJ (1978). "Distance determinations between the metal ion sites of Escherichia coli glutamine synthetase by electron paramagnetic resonance using Cr(III)--nucleotides as paramagnetic substrate analogues." Biochemistry 17(17);3531-8. PMID: 28753
Banerjee05: Banerjee S, Nandyala A, Podili R, Katoch VM, Hasnain SE (2005). "Comparison of Mycobacterium tuberculosis isocitrate dehydrogenases (ICD-1 and ICD-2) reveals differences in coenzyme affinity, oligomeric state, pH tolerance and phylogenetic affiliation." BMC Biochem 6;20. PMID: 16194279
Bender77: Bender RA, Janssen KA, Resnick AD, Blumenberg M, Foor F, Magasanik B (1977). "Biochemical parameters of glutamine synthetase from Klebsiella aerogenes." J Bacteriol 129(2);1001-9. PMID: 14104
CohenKupiec93: Cohen-Kupiec R, Gurevitz M, Zilberstein A (1993). "Expression of glnA in the cyanobacterium Synechococcus sp. strain PCC 7942 is initiated from a single nif-like promoter under various nitrogen conditions." J Bacteriol 175(23);7727-31. PMID: 7902350
ContrerasShanno05: Contreras-Shannon V, Lin AP, McCammon MT, McAlister-Henn L (2005). "Kinetic properties and metabolic contributions of yeast mitochondrial and cytosolic NADP+-specific isocitrate dehydrogenases." J Biol Chem 280(6);4469-75. PMID: 15574419
Coschigano98a: Coschigano KT, Melo-Oliveira R, Lim J, Coruzzi GM (1998). "Arabidopsis gls mutants and distinct Fd-GOGAT genes. Implications for photorespiration and primary nitrogen assimilation." Plant Cell 10(5);741-52. PMID: 9596633
Dahlquist75: Dahlquist FW, Purich DL (1975). "Regulation of Escherichia coli glutamine synthetase. Evidence for the action of some feedback modifiers at the active site of the unadenylylated enzyme." Biochemistry 14(9);1980-9. PMID: 235974
delaFuente08: de la Fuente van Bentem S, Anrather D, Dohnal I, Roitinger E, Csaszar E, Joore J, Buijnink J, Carreri A, Forzani C, Lorkovic ZJ, Barta A, Lecourieux D, Verhounig A, Jonak C, Hirt H (2008). "Site-specific phosphorylation profiling of Arabidopsis proteins by mass spectrometry and peptide chip analysis." J Proteome Res 7(6);2458-70. PMID: 18433157
Dhalla94: Dhalla AM, Li B, Alibhai MF, Yost KJ, Hemmingsen JM, Atkins WM, Schineller J, Villafranca JJ (1994). "Regeneration of catalytic activity of glutamine synthetase mutants by chemical activation: exploration of the role of arginines 339 and 359 in activity." Protein Sci 3(3);476-81. PMID: 7912599
Duckworth87: Duckworth HW, Anderson DH, Bell AW, Donald LJ, Chu AL, Brayer GD (1987). "Structural basis for regulation in gram-negative bacterial citrate synthases." Biochem Soc Symp 1987;54;83-92. PMID: 3333000
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