Determination of the cryptic stereochemistry of the first PKS chain-extension step in ansamitocin biosynthesis by Actinosynnema pretiosum

Takaaki Kubota, Marco Brünjes, Thomas Frenzel, Jun Xu, Andreas Kirschning, Heinz G. Floss

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

The biosynthesis of the antitumor antibiotic, ansamitocin, involves the assembly of a linear octaketide on the ansamitocin (asm) polyketide synthase (PKS), which is then cyclized to proansamitocin and further modified to the final product. In the first chain-extension step on the asm PKS, a stereocenter is generated which is then obliterated in a subsequent double-bond migration. The cryptic configuration at this stereocenter was determined by first synthesizing the two enantiomers of the intermediate diketide as their N-acetylcysteamine (SNAC) thioesters. These were then used to demonstrate that only the R enantiomer complements a 3-amino-5-hydroxybenzaic acid (AHBA) deficient mutant of Actinosynnema pretiosum to restore ansamitocin formation. The low efficiency of complementation by the diketide, compared to AHBA, is due to inefficient loading onto the PKS and not the inhibition of the enzyme. A presumed next chain-extension intermediate-the triketide with an unrearranged double bond-was also synthesized as its SNAC ester, but did not complement the AHBA- mutant.

Original languageEnglish
Pages (from-to)1221-1225
Number of pages5
JournalChemBioChem
Volume7
Issue number8
DOIs
Publication statusPublished - Aug 2006
Externally publishedYes

Keywords

  • Ansamitocin
  • Antitumor agents
  • Biosynthesis
  • Geldanamycin
  • Polyketides

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Organic Chemistry

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