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Literature summary extracted from

  • Torabinejad, J.; Donahue, J.L.; Gunesekera, B.N.; Allen-Daniels, M.J.; Gillaspy, G.E.
    VTC4 is a bifunctional enzyme that affects myoinositol and ascorbate biosynthesis in plants (2009), Plant Physiol., 150, 951-961.
    View publication on PubMedView publication on EuropePMC

Cloned(Commentary)

EC Number Cloned (Comment) Organism
3.1.3.B9 cloned into a plasmid construct containing the T7 viral promoter, an N-terminal polyhistidine peptide, an Xpress epitope, and an EK cleavage site (pAtIMPH). Overexpression of soluble VTC4 protein in Escherichia coli strain pREP4/BL21(DE3) Arabidopsis thaliana

Inhibitors

EC Number Inhibitors Comment Organism Structure
3.1.3.B9 Ca2+
-
 Arabidopsis thaliana
3.1.3.B9 Li+
-
 Arabidopsis thaliana
3.1.3.B9 additional information ascorbate is not an inhibitor of VTC4 Arabidopsis thaliana
3.1.3.93 D-inositol 3-phosphate substrate inhibition above 0.7 mM Arabidopsis thaliana

KM Value [mM]

EC Number KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
3.1.3.B9 0.107
-
 L-galactose 1-phosphate pH and temperature not specified in the publication Arabidopsis thaliana
3.1.3.93 0.107
-
 beta-L-galactose 1-phosphate pH 7.5, 22°C Arabidopsis thaliana
3.1.3.93 0.191
-
 D-inositol 3-phosphate pH 7.5, 22°C Arabidopsis thaliana

Localization

EC Number Localization Comment Organism GeneOntology No. Textmining

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
3.1.3.93 Mg2+ about 3fold activation, optimum concentration 3-4 mM Arabidopsis thaliana

Molecular Weight [Da]

EC Number Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
3.1.3.B9 33100
-
 x * 33100, calculated from sequence Arabidopsis thaliana
3.1.3.B9 39700
-
 x * 39700, SDS-PAGE Arabidopsis thaliana
3.1.3.93 33100
-
 x * 39700, SDS-PAGE, x * 33100, calculated Arabidopsis thaliana
3.1.3.93 39700
-
 x * 39700, SDS-PAGE, x * 33100, calculated Arabidopsis thaliana

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
3.1.3.B9 L-galactose 1-phosphate + H2O Arabidopsis thaliana
-
 L-galactose + phosphate
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
3.1.3.B9 Arabidopsis thaliana Q9M8S8
-
-
3.1.3.93 Arabidopsis thaliana Q9M8S8 bifunctional L-galactose 1-phosphate phosphatase/myo-inositol monophosphatase
-

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
3.1.3.B9 L-galactose 1-phosphate + H2O
-
 Arabidopsis thaliana L-galactose + phosphate
-
 ?
3.1.3.B9 L-galactose 1-phosphate + H2O the bifunctional enzyme VTC4 also acts on myo-inositol phosphate (cf. EC 3.1.3.25) Arabidopsis thaliana L-galactose + phosphate
-
 ?
3.1.3.93 alpha-D-glucose 1-phosphate + H2O 19% of the activity with myo-inositol Arabidopsis thaliana alpha-D-glucose + phosphate
-
 ?
3.1.3.93 beta-L-galactose 1-phosphate + H2O 166-240% of the activity with myo-inositol Arabidopsis thaliana L-galactose + phosphate
-
 ?
3.1.3.93 D-galactose 1-phosphate + H2O 16.6% of the activity with myo-inositol Arabidopsis thaliana D-galactose + phosphate
-
 ?
3.1.3.93 D-inositol 3-phosphate + H2O
-
 Arabidopsis thaliana D-inositol + phosphate
-
 ?
3.1.3.93 glycerol 2-phosphate + H2O 52% of the activity with myo-inositol Arabidopsis thaliana glycerol + phosphate
-
 ?
3.1.3.93 additional information Fru 1-phosphate, Fru 1,6-bisphosphate, Glc 6-phosphate, D-alpha-glycerophosphate, sorbitol 6-phosphate, and myo-inositol 2-V show little to no hydrolysis in assays Arabidopsis thaliana ?
-
 ?
3.1.3.93 myo-inositol 1-phosphate + H2O
-
 Arabidopsis thaliana myo-inositol + phosphate
-
 ?

Subunits

EC Number Subunits Comment Organism
3.1.3.B9 ? x * 39700, SDS-PAGE Arabidopsis thaliana
3.1.3.B9 ? x * 33100, calculated from sequence Arabidopsis thaliana
3.1.3.93 ? x * 39700, SDS-PAGE, x * 33100, calculated Arabidopsis thaliana

Synonyms

EC Number Synonyms Comment Organism
3.1.3.B9 At3g02870
-
 Arabidopsis thaliana
3.1.3.B9 VTC4
-
 Arabidopsis thaliana
3.1.3.93 VTC4
-
 Arabidopsis thaliana

pH Optimum

EC Number pH Optimum Minimum pH Optimum Maximum Comment Organism
3.1.3.93 7.5
-
-
 Arabidopsis thaliana

General Information

EC Number General Information Comment Organism
3.1.3.B9 malfunction knockout lines of VTC4 exhibit small perturbations in abscisic acid, salt, and cold responses. Analysis of metabolite levels in vtc4 mutants show that less myo-inositol and ascorbate accumulate in these mutants Arabidopsis thaliana
3.1.3.B9 physiological function VTC4 is a bifunctional enzyme that impacts both myo-inositol and ascorbate synthesis pathways Arabidopsis thaliana
3.1.3.93 physiological function knockout lines of isoform VTC4 exhibit small perturbations in abscisic acid, salt, and cold responses. Less myo-inositol and ascorbate accumulate in these mutants Arabidopsis thaliana