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MetaCyc Enzyme: xanthine-guanine phosphoribosyltransferase

Gene: gpt Accession Numbers: EG10414 (MetaCyc), b0238, ECK0239

Synonyms: glyD, gpp, gxu

Species: Escherichia coli K-12 substr. MG1655

Subunit composition of xanthine-guanine phosphoribosyltransferase = [Gpt]4

Summary:
Xanthine-guanine phosphoribosyltransferase is a purine salvage enzyme which converts either xanthine or guanine to XMP or GMP, respectively. It can also act on hypoxanthine, although guanine appears to be the preferred substrate [Liu83, Deo85].

Based on the native molecular weight obtained by gel filtration, the enzyme was originally thought to be a trimer in solution [Liu83], but was later found to be a homotetramer [Vos96, Vos97].

Crystal structures of the free, substrate- and product-bound forms of the enzyme have been solved, and a reaction mechanism has been proposed [Vos97, Vos98].

A gpt mutant is unable to grow on xanthine, but can still grow on guanine at a lower growth rate due to the presence of a second guanine phosphoribosyltransferase activity [Holden76]. An hpt gpt double mutant is extremely sensitive to inhibition by adenine [Levine81] due to the role of guanine phosphoribosyltransferase in converting free guanine to GMP when the cell is depleted for guanine nucleotides [Levine82].

The gpt gene has been used as a selectable marker for introduction of DNA into mammalian cell lines [Mulligan81].

The amino acid sequence of E. coli Gpt shares only 23% identity with E. coli Hpt, despite their common function [Guddat02]. This enzyme is one of three E. coli phosphoribosyltransferases (PRTases) that participate in purine salvage, Gpt, Hpt and Apt. They are classified as type I PRTases based on a conserved 5-phospho-α-D-ribosyl-1-pyrophosphate binding-site motif [Vos98].

Gpt: "guanine phosphoribosyltransferase" [Holden76]

Gxu: "guanine-xanthine utilization"

Locations: inner membrane, cytosol

Map Position: [255,977 -> 256,435]

Molecular Weight of Polypeptide: 16.971 kD (from nucleotide sequence), 18.6 kD (experimental) [Liu83 ]

Molecular Weight of Multimer: 65.0 kD (experimental) [Vos97]

pI: 5.85

Unification Links: ASAP:ABE-0000814 , EchoBASE:EB0409 , EcoGene:EG10414 , EcoliWiki:b0238 , Entrez-gene:944817 , ModBase:P0A9M5 , OU-Microarray:b0238 , PortEco:gpt , PR:PRO_000022834 , Pride:P0A9M5 , Protein Model Portal:P0A9M5 , RefSeq:NP_414773 , RegulonDB:EG10414 , SMR:P0A9M5 , String:511145.b0238 , UniProt:P0A9M5

Relationship Links: InterPro:IN-FAMILY:IPR000836 , InterPro:IN-FAMILY:IPR023747 , PDB:Structure:1A95 , PDB:Structure:1A96 , PDB:Structure:1A97 , PDB:Structure:1A98 , PDB:Structure:1NUL , Pfam:IN-FAMILY:PF00156 , Prosite:IN-FAMILY:PS00103

Gene-Reaction Schematic: ?

GO Terms:

Biological Process: GO:0032263 - GMP salvage Inferred from experiment [Holden76]
GO:0032264 - IMP salvage Inferred from experiment [Liu83]
GO:0032265 - XMP salvage Inferred from experiment Inferred by computational analysis [UniProtGOA12, Holden76]
GO:0006166 - purine ribonucleoside salvage Inferred by computational analysis [UniProtGOA11a, GOA06]
GO:0009116 - nucleoside metabolic process Inferred by computational analysis [GOA01a]
Molecular Function: GO:0000310 - xanthine phosphoribosyltransferase activity Inferred from experiment Inferred by computational analysis [GOA06, GOA01, GOA01a, Liu83]
GO:0004422 - hypoxanthine phosphoribosyltransferase activity Inferred from experiment [Liu83]
GO:0042802 - identical protein binding Inferred from experiment [Vos97]
GO:0000287 - magnesium ion binding Inferred by computational analysis [GOA06]
GO:0016740 - transferase activity Inferred by computational analysis [UniProtGOA11a]
GO:0016757 - transferase activity, transferring glycosyl groups Inferred by computational analysis [UniProtGOA11a]
GO:0046872 - metal ion binding Inferred by computational analysis [UniProtGOA11a]
Cellular Component: GO:0005829 - cytosol Inferred from experiment Inferred by computational analysis [DiazMejia09, Ishihama08, Lasserre06]
GO:0005886 - plasma membrane Inferred by computational analysis [UniProtGOA11, UniProtGOA11a, GOA06]
GO:0016020 - membrane Inferred by computational analysis [UniProtGOA11a]

MultiFun Terms: metabolism central intermediary metabolism nucleotide and nucleoside conversions

Credits:
Reviewed in EcoCyc 11-Feb-2010 by Sarker M
Imported from EcoCyc 16-Sep-2014 by Paley S , SRI International


Enzymatic reaction of: xanthine phosphoribosyltransferase (xanthine-guanine phosphoribosyltransferase)

Synonyms: XGPRT, XPRT, 5-phospho-α-D-ribose-1-diphosphate:xanthine phospho-D-ribosyltransferase, guanine phosphoribosyltransferase

EC Number: 2.4.2.22

xanthine + 5-phospho-α-D-ribose 1-diphosphate <=> XMP + diphosphate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

The reaction is physiologically favored in the direction shown.

In Pathways: xanthine and xanthosine salvage

Credits:
Imported from EcoCyc 16-Sep-2014 by Paley S , SRI International

Inhibitors (Unknown Mechanism): thioguanine [Deo85] , azaguanine [Deo85] , GMP [Liu83, Deo85] , XMP [Liu83, Comment 1] , IMP [Liu83, Comment 2]

Kinetic Parameters:

Substrate
Km (μM)
Citations
xanthine
39.0
[Liu83]
5-phospho-α-D-ribose 1-diphosphate
95.0
[Liu83]

pH(opt): 9.5 [Liu83]


Enzymatic reaction of: guanine phosphoribosyltransferase

Synonyms: XGPRT, xanthine phosphoribosyltransferase, 5-phospho-α-D-ribose-1-diphosphate:xanthine phospho-D-ribosyltransferase

EC Number: 2.4.2.8

guanine + 5-phospho-α-D-ribose 1-diphosphate <=> GMP + diphosphate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

The reaction is physiologically favored in the direction shown.

In Pathways: superpathway of guanine and guanosine salvage , guanine and guanosine salvage

Credits:
Imported from EcoCyc 16-Sep-2014 by Paley S , SRI International

Inhibitors (Unknown Mechanism): thioguanine [Deo85] , GMP [Deo85]


Enzymatic reaction of: hypoxanthine phosphoribosyltransferase (xanthine-guanine phosphoribosyltransferase)

Synonyms: XGPRT, xanthine phosphoribosyltransferase, 5-phospho-α-D-ribose-1-diphosphate:xanthine phospho-D-ribosyltransferase, guanine phosphoribosyltransferase

EC Number: 2.4.2.8

hypoxanthine + 5-phospho-α-D-ribose 1-diphosphate <=> IMP + diphosphate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

The reaction is physiologically favored in the direction shown.

In Pathways: adenine and adenosine salvage III

Credits:
Imported from EcoCyc 16-Sep-2014 by Paley S , SRI International

Kinetic Parameters:

Substrate
Km (μM)
Citations
hypoxanthine
167.0
[Liu83]


Sequence Features

Feature Class Location Citations Comment
Cleavage-of-Initial-Methionine 1
[Vos96]
 
Protein-Segment 37 -> 38
[UniProt10a]
UniProt: 5-phosphoribose 1-diphosphate binding; Sequence Annotation Type: region of interest;
Mutagenesis-Variant 59
[Vos96, UniProt11]
Alternate sequence: A; UniProt: No effect on catalytic activity; increased stability.
Amino-Acid-Sites-That-Bind 69
[UniProt10]
UniProt: 5-phosphoribose 1-diphosphate;
Metal-Binding-Site 89
[UniProt10]
UniProt: Magnesium;
Amino-Acid-Sites-That-Bind 92
[UniProt10]
UniProt: Xanthine;
Protein-Segment 92 -> 96
[UniProt10a]
UniProt: 5-phosphoribose 1-diphosphate binding; Sequence Annotation Type: region of interest;
Sequence-Conflict 122
[Richardson87, UniProt10]
Alternate sequence: G; UniProt: (in Ref. 5; AAA23933);
Amino-Acid-Sites-That-Bind 135
[UniProt10]
UniProt: Xanthine; via amide nitrogen and carbonyl oxygen;

History:
1/26/1998 (pkarp) Merged genes G8007/gpt and EG10414/gpt


References

Deo85: Deo SS, Tseng WC, Saini R, Coles RS, Athwal RS (1985). "Purification and characterization of Escherichia coli xanthine-guanine phosphoribosyltransferase produced by plasmid pSV2gpt." Biochim Biophys Acta 839(3);233-9. PMID: 3886014

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

GOA01: GOA, MGI (2001). "Gene Ontology annotation based on Enzyme Commission mapping." Genomics 74;121-128.

GOA01a: GOA, DDB, FB, MGI, ZFIN (2001). "Gene Ontology annotation through association of InterPro records with GO terms."

GOA06: GOA, SIB (2006). "Electronic Gene Ontology annotations created by transferring manual GO annotations between orthologous microbial proteins."

Guddat02: Guddat LW, Vos S, Martin JL, Keough DT, de Jersey J (2002). "Crystal structures of free, IMP-, and GMP-bound Escherichia coli hypoxanthine phosphoribosyltransferase." Protein Sci 11(7);1626-38. PMID: 12070315

Holden76: Holden JA, Harriman PD, Wall JD (1976). "Escherichia coli mutants deficient in guanine-xanthine phosphoribosyltransferase." J Bacteriol 126(3);1141-8. PMID: 820683

Ishihama08: Ishihama Y, Schmidt T, Rappsilber J, Mann M, Hartl FU, Kerner MJ, Frishman D (2008). "Protein abundance profiling of the Escherichia coli cytosol." BMC Genomics 9;102. PMID: 18304323

Lasserre06: Lasserre JP, Beyne E, Pyndiah S, Lapaillerie D, Claverol S, Bonneu M (2006). "A complexomic study of Escherichia coli using two-dimensional blue native/SDS polyacrylamide gel electrophoresis." Electrophoresis 27(16);3306-21. PMID: 16858726

Levine81: Levine RA, Taylor MW (1981). "Selection for purine regulatory mutants in an E. coli hypoxanthine phosphoribosyl transferase-guanine phosphoribosyl transferase double mutant." Mol Gen Genet 181(3);313-8. PMID: 6787390

Levine82: Levine RA, Taylor MW (1982). "Mechanism of adenine toxicity in Escherichia coli." J Bacteriol 149(3);923-30. PMID: 6801015

Liu83: Liu SW, Milman G (1983). "Purification and characterization of Escherichia coli guanine-xanthine phosphoribosyltransferase produced by a high efficiency expression plasmid utilizing a lambda PL promoter and CI857 temperature-sensitive repressor." J Biol Chem 1983;258(12);7469-75. PMID: 6305942

Mulligan81: Mulligan RC, Berg P (1981). "Selection for animal cells that express the Escherichia coli gene coding for xanthine-guanine phosphoribosyltransferase." Proc Natl Acad Sci U S A 78(4);2072-6. PMID: 7017722

Richardson87: Richardson KK, Richardson FC, Crosby RM, Swenberg JA, Skopek TR (1987). "DNA base changes and alkylation following in vivo exposure of Escherichia coli to N-methyl-N-nitrosourea or N-ethyl-N-nitrosourea." Proc Natl Acad Sci U S A 84(2);344-8. PMID: 3540961

UniProt10: UniProt Consortium (2010). "UniProt version 2010-11 released on 2010-11-02 00:00:00." Database.

UniProt10a: UniProt Consortium (2010). "UniProt version 2010-07 released on 2010-06-15 00:00:00." Database.

UniProt11: UniProt Consortium (2011). "UniProt version 2011-06 released on 2011-06-30 00:00:00." Database.

UniProtGOA11: UniProt-GOA (2011). "Gene Ontology annotation based on the manual assignment of UniProtKB Subcellular Location terms in UniProtKB/Swiss-Prot entries."

UniProtGOA11a: UniProt-GOA (2011). "Gene Ontology annotation based on manual assignment of UniProtKB keywords in UniProtKB/Swiss-Prot entries."

UniProtGOA12: UniProt-GOA (2012). "Gene Ontology annotation based on UniPathway vocabulary mapping."

Vos96: Vos S, de Jersey J, Martin JL (1996). "Crystallization and preliminary X-ray crystallographic studies of Escherichia coli xanthine phosphoribosyltransferase." J Struct Biol 116(2);330-4. PMID: 8812991

Vos97: Vos S, de Jersey J, Martin JL (1997). "Crystal structure of Escherichia coli xanthine phosphoribosyltransferase." Biochemistry 36(14);4125-34. PMID: 9100006

Vos98: Vos S, Parry RJ, Burns MR, de Jersey J, Martin JL (1998). "Structures of free and complexed forms of Escherichia coli xanthine-guanine phosphoribosyltransferase." J Mol Biol 282(4);875-89. PMID: 9743633


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Sat Nov 22, 2014, BIOCYC13A.