| Octaketide-producing type III polyketide synthase from Hypericum perforatum is expressed in dark glands accumulating hypericins. | |
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MedLine Citation:
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PMID: 18647343 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Hypericins are biologically active constituents of Hypericum perforatum (St John's wort). It is likely that emodin anthrone, an anthraquinone precursor of hypericins, is biosynthesized via the polyketide pathway by type III polyketide synthase (PKS). A PKS from H. perforatum, HpPKS2, was investigated for its possible involvement in the biosynthesis of hypericins. Phylogenetic tree analysis revealed that HpPKS2 groups with functionally divergent non-chalcone-producing plant-specific type III PKSs, but it is not particularly closely related to any of the currently known type III PKSs. A recombinant HpPKS2 expressed in Escherichia coli resulted in an enzyme of approximately 43 kDa. The purified enzyme catalysed the condensation of acetyl-CoA with two to seven malonyl-CoA to yield tri- to octaketide products, including octaketides SEK4 and SEK4b, as well as heptaketide aloesone. Although HpPKS2 was found to have octaketide synthase activity, production of emodin anthrone, a supposed octaketide precursor of hypericins, was not detected. The enzyme also accepted isobutyryl-CoA, benzoyl-CoA and hexanoyl-CoA as starter substrates producing a variety of tri- to heptaketide products. In situ RNA hybridization localized the HpPKS2 transcripts in H. perforatum leaf margins, flower petals and stamens, specifically in multicellular dark glands accumulating hypericins. Based on our results, HpPKS2 may have a role in the biosynthesis of hypericins in H. perforatum but some additional factors are possibly required for the production of emodin anthrone in vivo. |
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Authors:
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Katja Karppinen; Juho Hokkanen; Sampo Mattila; Peter Neubauer; Anja Hohtola |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2008-07-21 |
Journal Detail:
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Title: The FEBS journal Volume: 275 ISSN: 1742-464X ISO Abbreviation: FEBS J. Publication Date: 2008 Sep |
Date Detail:
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Created Date: 2008-08-15 Completed Date: 2008-10-03 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 101229646 Medline TA: FEBS J Country: England |
Other Details:
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Languages: eng Pagination: 4329-42 Citation Subset: IM |
Affiliation:
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Department of Biology, University of Oulu, Finland. katja.karppinen@oulu.fi |
| Data Bank Information | |
Bank Name/Acc. No.:
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GENBANK/EU635882 |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Base Sequence Chromatography, Liquid DNA Primers Escherichia coli / genetics Hypericum / enzymology* In Situ Hybridization Molecular Sequence Data Perylene / analogs & derivatives*, metabolism Phylogeny Polyketide Synthases / genetics, isolation & purification*, metabolism RNA Probes Recombinant Proteins / genetics, isolation & purification, metabolism Spectrometry, Mass, Electrospray Ionization |
| Chemical | |
Reg. No./Substance:
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0/DNA Primers; 0/RNA Probes; 0/Recombinant Proteins; 198-55-0/Perylene; 548-04-9/hypericin; 79956-01-7/Polyketide Synthases |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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