- Unveiling Two Consecutive Hydroxylations: Mechanisms of Aromatic Hydroxylations Catalyzed by Flavin-Dependent Monooxygenases for the Biosynthesis of Actinorhodin and Related Antibiotics
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Flavin-dependent monooxygenases are ubiquitous in living systems and are classified into single- or two-component systems. Actinorhodin, produced by Streptomyces coelicolor, is a representative polycyclic polyketide that is hydroxylated through the action of the two-component ActVA-5/ActVB hydroxylase system. These homologous systems are widely distributed in bacteria, but their reaction mechanisms remain unclear. This in vitro investigation has provided chemical proof of two consecutive hydroxylations via hydroxynaphthalene intermediates involved in actinorhodin biosynthesis. The ActVA-5 oxygenase component catalyzed a stepwise dihydroxylation of the substrate, whereas the ActVB flavin reductase not only supplied a reduced cofactor, but also regulated the quinone–hydroquinone interconversion of an intermediate. Our study provides clues for understanding the general biosynthetic mechanisms of highly functionalized aromatic natural products with structural diversity.
- Hashimoto, Makoto,Taguchi, Takaaki,Ishikawa, Kazuki,Mori, Ryuichiro,Hotta, Akari,Watari, Susumu,Katakawa, Kazuaki,Kumamoto, Takuya,Okamoto, Susumu,Ichinose, Koji
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p. 623 - 627
(2019/12/15)
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- Epoxyquinone formation catalyzed by a two-component flavin-dependent monooxygenase involved in biosynthesis of the antibiotic actinorhodin
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The biosynthetic gene cluster of the aromatic polyketide antibiotic actinorhodin (ACT) in Streptomyces coelicolor A3(2) carries a pair of genes, actVA-ORF5 and actVB, that encode a two-component flavin-dependent monooxygenase (FMO). Our previous studies have demonstrated that the ActVA-ORF5/ActVB system functions as a quinone-forming C-6 oxygenase in ACT biosynthesis. Furthermore, we found that this enzyme system exhibits an additional oxygenation activity with dihydrokalafungin (DHK), a proposed intermediate in the ACT biosynthetic pathway, and generates two reaction products. These compounds were revealed to be monooxygenated derivatives of kalafungin, which is spontaneously formed through oxidative lactonization of DHK. Their absolute structures were elucidated from their NMR spectroscopic data and by computer modeling and X-ray crystallography as (5S,14R)-epoxykalafungin and (5R,14S)-epoxykalafungin, demonstrating an additional epoxyquinone-forming activity of the ActVA-ORF5/ActVB system in vitro.
- Taguchi, Takaaki,Okamoto, Susumu,Hasegawa, Kimiko,Ichinose, Koji
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experimental part
p. 2767 - 2773
(2012/04/10)
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- Enantiodivergent total syntheses of nanaomycins and their enantiomers, kalafungins
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The first, enantiospecific total syntheses of pyranonaphthoquinone antibiotics, nanaomycins D and A, and their enantiomers kalafungin and 4-deoxykalafunginic acid, are described by an 'enantiodivergent' strategy from a common optically active intermediate, (1S,3RS,4S)-3,4-dihydro-5,9,10-trimethoxy-1-methyl-1H-naphtho[2,3-c]pyr an-3,4-diol, which has been derived from L-rhamnose via condensation of 4-methoxy-3-(phenylsulfonyl)-1-(3H)-isobenzofuranone and methyl 3,4,6-trideoxy-α-L-glycero-hex-3-enopyranosid-2-ulose.
- Tatsuta,Akimoto,Annaka,et al.
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p. 1699 - 1706
(2007/10/02)
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