Information on EC 2.5.1.115 - homogentisate phytyltransferase

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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria

EC NUMBER
COMMENTARY hide
2.5.1.115
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RECOMMENDED NAME
GeneOntology No.
homogentisate phytyltransferase
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REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
phytyl diphosphate + homogentisate = diphosphate + 2-methyl-6-phytylbenzene-1,4-diol + CO2
show the reaction diagram
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
vitamin E biosynthesis (tocopherols)
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vitamin E metabolism
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Ubiquinone and other terpenoid-quinone biosynthesis
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Metabolic pathways
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Biosynthesis of secondary metabolites
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SYSTEMATIC NAME
IUBMB Comments
phytyl diphosphate:homogentisate phytyltransferase
Requires Mg2+ for activity [3]. Involved in the biosynthesis of the vitamin E tocopherols. While the enzyme from the cyanobacterium Synechocystis PCC 6803 has an appreciable activity with geranylgeranyl diphosphate (EC 2.5.1.116, homogentisate geranylgeranyltransferase), the enzyme from the plant Arabidopsis thaliana has only a low activity with that substrate [1,3,4].
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
malfunction
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disruption of Synechocystis sp. PCC 6803 HPT function causes an absence of tocopherols without affecting plastoquinone-9 levels, indicating that separate polyprenyltransferases exist for tocopherol and plastoquinone synthesis in Synechocystis sp. PCC 6803
physiological function
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
geranylgeranyl diphosphate + homogentisate
?
show the reaction diagram
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?
geranylgeranyl diphosphate + homogentisate
diphosphate + 2-methyl-6-geranylgeranylbenzene-1,4-diol + CO2
show the reaction diagram
geranylgeranyl diphosphate + homogentisate
diphosphate + 6-geranylgeranyl-2-methylbenzene-1,4-diol + CO2
show the reaction diagram
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about 18% of the activity with phythyldiphosphate
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?
phythyl diphosphate + homogentisate
diphosphate + 2-methyl-6-phytylbenzene-1,4-diol + CO2
show the reaction diagram
phytyl diphosphate + homogentisate
diphosphate + 2-methyl-6-phytylbenzene-1,4-diol + CO2
show the reaction diagram
additional information
?
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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
phytyl diphosphate + homogentisate
diphosphate + 2-methyl-6-phytylbenzene-1,4-diol + CO2
show the reaction diagram
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Co2+
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5-10fold less stimulation than Mg2+
Mg2+
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best activator, optimum concentration 2 mM
Mn2+
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5-10fold less stimulation than Mg2+
additional information
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divalent cation required
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
n-dodecyl beta-D-maltoside
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stimulation at low concentration, strong inhibition above 0.1 mM
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
n-dodecyl beta-D-maltoside
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stimulation at low concentration, strong inhibition above 0.1 mM
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.006
homogentisate
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pH 7.5, 28°C
0.001
phythyl diphosphate
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pH 7.5, 28°C
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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gene expression level gradually decreases during fruit ripening, reaching a background level in ripened apple fruits
Manually annotated by BRENDA team
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expression in Escherichia coli
EXPRESSION
ORGANISM
UNIPROT
LITERATURE
abiotic stress results in an 18 and 8fold increase in total tocopherol content in wild-type and isoform HPT1 overexpressing leaves, respectively, with tocopherol levels in the ovrexpressing strain being 2- to 4fold higher than wild type at all experimental time points. Increased total tocopherol levels correlate with elevated HPT mRNA levels and HPT specific activity
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
nutrition
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in leaves, isoform HPT1 constitutive overexpression results in a 10fold increase in HPT specific activity and a 4.4fold increase in total tocopherol content relative to wild type. In seeds, HPT1 overexpression results in a 4fold increase in HPT specific activity and a total seed tocopherol content that is 40% higher than wild type, primarily because of an increase in gamma-tocopherol content. This enlarged pool of gamma-tocopherol is almost entirely converted to alpha-tocopherol by crossing HPT1 overexpressing plants with lines constitutively overexpressing gamma-tocopherol methyltransferase. Seed of the resulting double-overexpressing lines displays a 12fold increase in vitamin E activity relative to wild type