Information on EC 2.3.1.B25 - octaketide synthase

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The expected taxonomic range for this enzyme is: Aloe

EC NUMBER
COMMENTARY hide
2.3.1.B25
preliminary BRENDA-supplied EC number
RECOMMENDED NAME
GeneOntology No.
octaketide synthase
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REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
16 malonyl-CoA + 28 H+ = 16 CoA + 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-2-methyl-2,3-dihydro-4H-chromen-4-one + 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-5-methyl-2,3-dihydro-4H-chromen-4-one + 16 CO2 + 16 H2O
show the reaction diagram
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SYSTEMATIC NAME
IUBMB Comments
malonyl-CoA:malonyl-CoA C-malonyltransferase (oktaketide-forming)
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
evolution
physiological function
the oktaketide synthase is involved in the biosynthesis of anthrones and anthraquinones in the medicinal plant
additional information
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
8 malonyl-CoA
8 CoA + 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-2-methyl-2,3-dihydro-4H-chromen-4-one + 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-5-methyl-2,3-dihydro-4H-chromen-4-one + 8 CO2 + H2O
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
8 malonyl-CoA
8 CoA + 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-2-methyl-2,3-dihydro-4H-chromen-4-one + 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-5-methyl-2,3-dihydro-4H-chromen-4-one + 8 CO2 + H2O
show the reaction diagram
Q3L7F5
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additional information
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Q3L7F5
the oktaketide synthase reaction is also catalyzed by chalcone synthase (EC 2.3.1.74) mutant T197G/G256L/S338V, CHS containing a double point mutation G256L/S338V not only accepts 4coumaroyl-CoA but also biosynthesizes octaketides SEK4 and 4b, exhausting eight malonyl-CoAs
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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adventitious root
Manually annotated by BRENDA team
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
44000
x * 44000, about, sequence calculation
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
?
x * 44000, about, sequence calculation
Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
DNA and amino acid sequence determination and analysis, sequence comparison and phylogenetic analysis
EXPRESSION
ORGANISM
UNIPROT
LITERATURE
treatment with salicylic acid leads to increased expression of octaketide synthase genes and decreases in malonyl-CoA, with concomitant accumulation of Aloe emodin and chrysophanol
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
G197A
site-directed mutagenesis, the mutant enzyme shows altered activity compared to the wild-type enzyme producing heptaketides
G197T
site-directed mutagenesis, the mutant enzyme shows altered activity compared to the wild-type enzyme producing hexaketides
G197W
site-directed mutagenesis, the mutant enzyme shows altered activity compared to the wild-type enzyme producing tri- and pentaketides
G207A
site-directed mutagenesis, the G207A mutant loses the octaketide-forming activity and yields the heptaketide aloesone in addition to 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-2-methyl-2,3-dihydro-4H-chromen-4-one/2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-5-methyl-2,3-dihydro-4H-chromen-4-one
G207F
site-directed mutagenesis, the bulky substitution G207F mutant loses the octaketide-forming activity and yields the pentaketide 2,7-dihydroxy-5-methylchromone
G207L
site-directed mutagenesis, the bulky substitution G207F mutant loses the octaketide-forming activity and yields the pentaketide 2,7-dihydroxy-5-methylchromone
G207M
site-directed mutagenesis, OKS G207M mutant completely loses the octaketide-forming activity, but efficiently produces an unnatural pentaketide, 2,7-dihydroxy-5-methylchromone, from five molecules of malonyl-CoA, not a 5,7-diydroxy-5-methylchromne like the pentaketide chromone synthase, EC 2.3.1.216
G207T
site-directed mutagenesis, the G207T mutant loses the octaketide-forming activity and yields a hexaketide, 6-(2,4-dihydroxy-6-methylphenyl)-4-methoxy-2-pyrone, from six molecules of malonyl-CoA
G207W
site-directed mutagenesis, the mutant loses the octaketide-forming activity and yields a tetraketide, tetracetic acid lactone, along with the triketide, triacetic acid lactone, without the formation of an aromatic ring system
additional information
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
molecular biology
use of octaketide synthase for rational biosynthetic engineering to generate molecular diversity and pursue innovative, biologically potent compounds