Information on EC 2.7.7.45 - guanosine-triphosphate guanylyltransferase

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
2.7.7.45
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RECOMMENDED NAME
GeneOntology No.
guanosine-triphosphate guanylyltransferase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
2 GTP = diphosphate + P1,P4-bis(5'-guanosyl) tetraphosphate
show the reaction diagram
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
nucleotidyl group transfer
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SYSTEMATIC NAME
IUBMB Comments
GTP:GTP guanylyltransferase
Also acts, more slowly, on GDP to form P1,P3-bis(5'-guanosyl) triphosphate.
CAS REGISTRY NUMBER
COMMENTARY hide
54576-89-5
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
brine shrimp
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Manually annotated by BRENDA team
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-
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Manually annotated by BRENDA team
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-
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Manually annotated by BRENDA team
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
5'-guanylylimidodiphosphate + diphosphate
GppNHppG + diphosphate
show the reaction diagram
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-
-
?
dGTP + dGTP
P1,P4-bis(5'-(2'-deoxyguanosyl) tetraphosphate + diphosphate
show the reaction diagram
GDP + GDP
P1,P3-bis(5'-guanosyl)triphosphate + diphosphate
show the reaction diagram
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rate of the reaction is low compared with synthesis of P1,P4-bis(5'-guanosyl)tetraphosphate and dependent on other small molecular weight components of yolk platelets
i.e. GP3G
r
GDP + P1,P4-bis(5'-guanosyl)tetraphosphate
P1,P3-bis(5'-guanosyl)triphosphate
show the reaction diagram
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-
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r
GTP + GTP
diphosphate + P1,P4-bis(5'-guanosyl)tetraphosphate
show the reaction diagram
GTP + GTP
P1,P4-bis(5'-guanosyl)tetraphosphate + diphosphate
show the reaction diagram
GTP + guanosine 5'-tetraphosphate
diguanosine 5',5'''-P1,P5-pentaphosphate + diphosphate
show the reaction diagram
-
-
i.e. GP5G
r
GTP + ITP
GppppI + diphosphate
show the reaction diagram
GTP + P1,P4-bis(5'-guanosyl)tetraphosphate
GTP + ?
show the reaction diagram
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-
-
-
r
GTP + XTP
GppppX + diphosphate
show the reaction diagram
P1,P4-bis(5'-guanosyl)tetraphosphate + carbonyldiphosphonate
GTP + ?
show the reaction diagram
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29% of GTP-forming activity with diphosphate as second substrate
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r
P1,P4-bis(5'-guanosyl)tetraphosphate + cyclotriphosphate
GTP + ?
show the reaction diagram
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200% of GTP-forming activity with diphosphate as second substrate
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r
P1,P4-bis(5'-guanosyl)tetraphosphate + methylenediphosphonate
GTP + ?
show the reaction diagram
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25% of GTP-forming activity with diphosphate as second substrate
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r
P1,P4-bis(5'-guanosyl)tetraphosphate + tripolyphosphate
GTP + ?
show the reaction diagram
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75% of GTP-forming activity with diphosphate as second substrate
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r
additional information
?
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either 2 enzymes are present in guanosine-triphosphate guanylyltransferase preparations or 2 catalytic sites exist on one protein, one for the synthesis of P1,P3-bis(5'-guanosyl)triphosphate and one for the synthesis of P1,P4-bis(5'-guanosyl)tetraphosphate
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
GTP + GTP
diphosphate + P1,P4-bis(5'-guanosyl)tetraphosphate
show the reaction diagram
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Cu2+
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28% of the activity with Mg2+ in P1,P4-bis(5'-guanosyl)tetraphosphate synthesis
Mn2+
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86% of the activity with Mg2+ in P1,P4-bis(5'-guanosyl)tetraphosphate synthesis
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
diphosphate
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ITP
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partially uncompetitive inhibition of P1,P3-bis(5'-guanosyl)triphosphate synthesis
XTP
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uncompetitive inhibition of P1,P4-bis(5'-guanosyl)tetraphosphate synthesis
additional information
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no inhibition by phosphate
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.84
diphosphate
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pH 5.9, 40C
1.06
Gp4G
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pH 5.9, 40C
2.2 - 6.7
GTP
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
1.2 - 1.6
GTP
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
0.003 - 0.0066
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partially purified enzyme
0.113
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purified enzyme
additional information
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
5.9
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assay at
pH RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
4.5 - 8
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no activity below and above
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
37
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P1,P3-bis(5'-guanosyl)triphosphate synthesis, partially purified enzyme, Sephadex G-25 fraction
40 - 42
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P1,P4-bis(5'-guanosyl)tetraphosphate synthesis
43
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assay at
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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encysted, yolk platelets of
Manually annotated by BRENDA team
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
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small amount of activity
Manually annotated by BRENDA team
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
80000
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2 * 142000, alpha + 2 * 80000, beta, SDS-PAGE
110000
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x * 110000, SDS-PAGE
142000
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2 * 142000, alpha + 2 * 80000, beta, SDS-PAGE
480000
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gel filtration
490000
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gel filtration
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
?
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x * 110000, SDS-PAGE
tetramer
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2 * 142000, alpha + 2 * 80000, beta, SDS-PAGE
pH STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
37
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20 min, 0.2 M hydroxylamine, pH 7.5, 2.5% of maximal activity; 20 min, 3.68 M hydroxylamine, pH 4.75, 0.7% of maximal activity; 20 min, 4 M sodium acetate, pH 7.5, 96% of maximal activity
85
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5 min: stable at alkaline conditions of 0.15 M NaOH, 79.1% of maximal activity at pH 7.5, 1% of maximal activity at acidic conditions of 0.15 M HCl
GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
albumin, 10 mg/ml, glycerol, 30% or P1,P4-bis(5'-guanosyl)tetraphosphate, 0.6 mM, prevents loss of activity at 0C, Gp4G most effective
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STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
0C or -15C, 50% loss of activity after 1 week in buffered 500 mM NaCl
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
1687fold to homogeneity
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