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The Study of the Step of Post-PKS Tailoring Process of GDM Biosynthesis in Streptomyces Hygroscopicus 17997

Author: JiaChangHong
Tutor: WuLinZhuan
School: Beijing Union Medical College
Course: Microbial and Biochemical Pharmacy
Keywords: Streptomyces hygroscopicus 17997 geldanamycin (GDM) geldanamycin hydroquinone 17-O-demethylreblastatin biosynthesis post-PKS tailoring
CLC: R915
Type: Master's thesis
Year: 2011
Downloads: 42
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Abstract


In order to obtain some detail(s) of the post-PKS tailoring process of geldanamycin (GDM) biosynthesis, we analyzed the secondary metabolites produced by Streptomyces hygroscopicus 17997, its gdmN and gdmP mutants. The ethyl acetate extracts of these strains, cultured on ISPII medium plates at different culture times, were first separated by silica gel TLC, followed by alkaline color reaction for preliminary discrimination of GDM and its biosynthetic intermediate(s). LC-MS was then utilized for confirming the interested GDM biosynthetic intermediate(s). At a culture period of 72-96h, geldanamycin hydroquinone (GQH2), 4,5-dihydro-7-descarbamoyl-7-hydroxygeldanamycin hydroquinone (H2GQH2-dC) or 4,5-dihydrogeldanamycin hydroquinone (H2GQH2) appeared as the main component, while the corresponding quinone as the minor component, of Streptomyces hygroscopicus 17997, its gdmN or gdmP disruption mutant, respectively. These hydroquinones dissappeared gradually in older cultures and the corresponding quinones became the main components.A non-benzoquinone geldanamycin analogue,17-O-demethylreblastatin was found to exist in the fermentation broths of Streptomyces hygroscopicus 17997 and its gdmP disruption mutant. The compound could be partially bioconversed to geldanamycin upon a longer time (3d) incubation with a GDM-pks- disruption mutant of Streptomyces hygroscopicus 17997, suggesting that it was a subnormal intermediate of geldanamycin biosynthesis. As a result, an order of benzoquinone modifications of post-PKS tailoring process in geldanamycin biosynthesis was proposed, in which C-17 hydroxylation took place after C-21 hydroxylation. Spontaneous oxidation of GQH2 to GDM is suggested as the last step of the post-PKS tailoring process of GDM biosynthesis in Streptomyces hygroscopicus 17997.

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