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Literature summary for 2.3.1.B25 extracted from
- Engineering of plant polyketide biosynthesis (2008), Chem. Pharm. Bull., 56, 1505-1514.
Cloned(Commentary)
| Cloned (Comment) | Organism |
|---|---|
| DNA and amino acid sequence determination and analysis, sequence comparison and phylogenetic analysis | Aloe arborescens |
Protein Variants
| Protein Variants | Comment | Organism |
|---|---|---|
| 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 | Aloe arborescens |
| G207F | site-directed mutagenesis, the bulky substitution G207F mutant loses the octaketide-forming activity and yields the pentaketide 2,7-dihydroxy-5-methylchromone | Aloe arborescens |
| G207L | site-directed mutagenesis, the bulky substitution G207F mutant loses the octaketide-forming activity and yields the pentaketide 2,7-dihydroxy-5-methylchromone | Aloe arborescens |
| 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 | Aloe arborescens |
| 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 | Aloe arborescens |
| 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 | Aloe arborescens |
| additional information | oktaketide synthase, EC 2.3.1.OKS, and pentaketide chromone synthase, EC 2.3.1.216, are not functionally interconvertible by the single amino acid switch at residue 207 | Aloe arborescens |
Molecular Weight [Da]
| Molecular Weight [Da] | Molecular Weight Maximum [Da] | Comment | Organism |
|---|---|---|---|
| 44000 | - |
x * 44000, about, sequence calculation | Aloe arborescens |
Natural Substrates/ Products (Substrates)
| Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| 8 malonyl-CoA | Aloe arborescens | - |
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 | - |
? |  |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Aloe arborescens | Q3L7F5 | - |
- |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| 8 malonyl-CoA | - |
Aloe arborescens | 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 | - |
? | |
| 8 malonyl-CoA | - |
Aloe arborescens | 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 | i.e. SEK4 and SEK4b | ? | |
| additional information | recombinant oktaketide synthase catalyzes sequential condensations of eight molecules of malonyl-CoA to yield a 1:4 mixture of aromatic octaketides, 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-2-methyl-2,3-dihydro-4H-chromen-4-one and 2,7-dihydroxy-5-[(4-hydroxy-2-oxo-2H-pyran-6-yl)methyl]-5-methyl-2,3-dihydro-4H-chromen-4-one, which are the longest polyketides generated by the structurally simple type III polyketide synthase. Recombinant oktaketide synthase accepts acetyl-CoA, resulting from decarboxylation of malonyl-CoA, as a starter substrate | Aloe arborescens | ? | - |
? | |
Subunits
| Subunits | Comment | Organism |
|---|---|---|
| ? | x * 44000, about, sequence calculation | Aloe arborescens |
Synonyms
| Synonyms | Comment | Organism |
|---|---|---|
| OKS | - |
Aloe arborescens |
General Information
| General Information | Comment | Organism |
|---|---|---|
| evolution | pentaketide chromone synthase is a plant-specific type III polyketide synthase that belongs to the chalcone synthase superfamily of type III polyketide synthases and grouped with other non-chalcone forming enzymes | Aloe arborescens |
| additional information | the critical active-site residue 197, and the catalytic triad, Cys164, His303, and Asn336, are conserved in type III polyketide synthases, while the residues lining the active-site are exchanged to G197, L256, V338 (numbering in Madia sativa CHS). Active-site architecture of pentaketide chromone synthase compared to other type III polhaseyketide synt, crystal structure and hmology modeling, overview | Aloe arborescens |
| physiological function | the oktaketide synthase is involved in the biosynthesis of anthrones and anthraquinones in the medicinal plant | Aloe arborescens |
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