Information on EC 3.2.2.25 - N-methyl nucleosidase

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
3.2.2.25
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RECOMMENDED NAME
GeneOntology No.
N-methyl nucleosidase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
7-methylxanthosine + H2O = 7-methylxanthine + D-ribose
show the reaction diagram
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
Biosynthesis of secondary metabolites
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caffeine biosynthesis I
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caffeine biosynthesis II (via paraxanthine)
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Caffeine metabolism
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Metabolic pathways
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theobromine biosynthesis I
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SYSTEMATIC NAME
IUBMB Comments
7-methylxanthosine ribohydrolase
The enzyme preferentially hydrolyses 3- and 7-methylpurine nucleosides, such as 3-methylxanthosine, 3-methyladenosine and 7-methylguanosine. Hydrolysis of 7-methylxanthosine to form 7-methylxanthine is the second step in the caffeine-biosynthesis pathway.
CAS REGISTRY NUMBER
COMMENTARY hide
72270-62-3
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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Manually annotated by BRENDA team
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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
1-methyladenosine + H2O
1-methyladenine + D-ribose
show the reaction diagram
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22% of the activity with 7-methylxanthosine, substrate as 7-methyladenosine perchlorate
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ir
1-methylinosine + H2O
1-methylhypoxanthine + D-ribose
show the reaction diagram
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9% of the activity with 7-methylxanthosine
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ir
1-methylxanthosine + H2O
1-methylxanthine + D-ribose
show the reaction diagram
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12% of the activity with 7-methylxanthosine
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ir
3-methyladenosine + H2O
3-methyladenine + D-ribose
show the reaction diagram
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178% of the activity with 7-methylxanthosine, substrate as 3-methyladenosine p-toluenesulfonate
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ir
3-methylguanosine + H2O
3-methylguanine + D-ribose
show the reaction diagram
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38% of the activity with 7-methylxanthosine
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ir
3-methylinosine + H2O
3-methylhypoxanthine + D-ribose
show the reaction diagram
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128% of the activity with 7-methylxanthosine
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ir
3-methylxanthosine + H2O
3-methylxanthine + D-ribose
show the reaction diagram
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198% of the activity with 7-methylxanthosine
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ir
7-methyladenosine + H2O
7-methyladenine + D-ribose
show the reaction diagram
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13% of the activity with 7-methylxanthosine
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ir
7-methylguanosine + H2O
7-methylguanine + D-ribose
show the reaction diagram
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189% of the activity with 7-methylxanthosine
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ir
7-methylinosine + H2O
7-methylhypoxanthine + D-ribose
show the reaction diagram
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121% of the activity with 7-methylxanthosine
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ir
7-methylxanthosine + H2O
7-methylxanthine + D-ribose
show the reaction diagram
additional information
?
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substrate specificity, overview, no activity with 1-methylguanosine and guanosine, poor activity with inosine and adenosine
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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
7-methylxanthosine + H2O
7-methylxanthine + D-ribose
show the reaction diagram
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Mg2+
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slightly stimulating
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
7-Methylhypoxanthine
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50% inhibition at 5 mM, no inhibition at 1 mM
7-methylxanthine
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40% inhibition at 5 mM, no inhibition at 1 mM
Ca2+
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slight inhibition
Cu2+
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slight inhibition
EDTA
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90 inhibition at 1 mM
PCMB
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80% inhibition at 0.5 mM
Zn2+
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slight inhibition
additional information
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no inhibitin by Mg2+, Fe2+, Co2+, NaF, and iodoacetate
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
0.00656
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partially purified enzyme, after anion exchange chromatography
0.0294
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purified enzyme
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
8.5
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assay at
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
30
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assay at
37
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assay at
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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immature and ripe
Manually annotated by BRENDA team
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
55000
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gel filtration
pH STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
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the purified enzyme is unstable in acidic medium
137101
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
native enzyme from leaves, separated from adenosine nucleosidase, EC 3.2.2.7, by anion exchange chromatography, followed by hydroxylapatite chromatography and gel filtration, to homogeneity
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