This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Nucleosides and Nucleotides Biosynthesis → Purine Nucleotide Biosynthesis → Purine Nucleotide Salvage → Guanine and Guanosine Salvage|
Guanosine nucleotides can be synthesized de novo. In that route GMP (GMP) is synthesized via IMP (IMP) and XMP (XMP) , which is converted to GMP by the action of GMP synthetase, an enzyme that can use either glutamine or ammonia as substrate (see superpathway of guanosine nucleotides de novo biosynthesis II). Note that the free base guanine or the ribonucleoside guanosine are not produced via the de novo pathway.
Many organisms can also recycle guanosine nucleotides by a combination of degradation and salvage pathways. The degradation pathway is responsible for the degradation of the nucleotides to the nucleoside guanosine and the base guanine, which can be further degraded via xanthine and urate, and eventually catabolized to basic building blocks (see superpathway of guanosine nucleotides degradation (plants)).
The enzyme inosine-guanosine kinase (EC 22.214.171.124), which has been studied in Escherichia coli, can phosphorylate guanosine directly to the mono-nucleotide GMP. Even though genes encoding this enzyme have been identified only in bacteria and archaea [Kawasaki00], this activity has also been reported for artichoke, Helianthus tuberosus [Combes89].
Either of these routes enables the organism to salvage the degradation products of guanosine nucleotides, and recycle them back to nucleotide form.
Superpathways: superpathway of guanine and guanosine salvage
Unification Links: EcoCyc:PWY-6618
Combes89: Combes, Agnes, Lafleuriel, Jacqueline, Le Floc'h, Francois (1989). "The inosine-guanosine kinase activity of mitochondria in tubers of Jerusalem artichoke." Plant Physiol. Biochem. 27(5):729-736.
Kawasaki00: Kawasaki H, Shimaoka M, Usuda Y, Utagawa T (2000). "End-product regulation and kinetic mechanism of guanosine-inosine kinase from Escherichia coli." Biosci Biotechnol Biochem 2000;64(5);972-9. PMID: 10879466
Butland05: Butland G, Peregrin-Alvarez JM, Li J, Yang W, Yang X, Canadien V, Starostine A, Richards D, Beattie B, Krogan N, Davey M, Parkinson J, Greenblatt J, Emili A (2005). "Interaction network containing conserved and essential protein complexes in Escherichia coli." Nature 433(7025);531-7. PMID: 15690043
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Jochimsen75: Jochimsen B, Nygaard P, Vestergaard T (1975). "Location on the chromosome of Escherichia coli of genes governing purine metabolism. Adenosine deaminase (add), guanosine kinase (gsk) and hypoxanthine phosphoribosyltransferase (hpt)." Mol Gen Genet 1975;143(1);85-91. PMID: 765747
Matsui01a: Matsui H, Shimaoka M, Takenaka Y, Kawasaki H, Kurahashi O (2001). "gsk disruption leads to guanosine accumulation in Escherichia coli." Biosci Biotechnol Biochem 65(5);1230-5. PMID: 11440147
Mori95: Mori H, Iida A, Teshiba S, Fujio T (1995). "Cloning of a guanosine-inosine kinase gene of Escherichia coli and characterization of the purified gene product." J Bacteriol 177(17);4921-6. PMID: 7665468
Rajagopala14: Rajagopala SV, Sikorski P, Kumar A, Mosca R, Vlasblom J, Arnold R, Franca-Koh J, Pakala SB, Phanse S, Ceol A, Hauser R, Siszler G, Wuchty S, Emili A, Babu M, Aloy P, Pieper R, Uetz P (2014). "The binary protein-protein interaction landscape of Escherichia coli." Nat Biotechnol 32(3);285-90. PMID: 24561554
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