Mechanistic Studies of the Biosynthesis of 3,6‐Dideoxysugars in Bacteria: Exploration of a Novel C‐O Bond Cleavage Event

Hung‐Wen ‐W Liu, Jon S. Thorson, Vaughn P. Miller, Theresa M. Kelley, Yenyoung Lei, Olivier Ploux, Xuemei He, Ding‐Yah ‐Y Yang

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3 Scopus citations


Deoxy sugars are ubiquitous in nature and contribute to diverse biological activities. Attempts to design systems to control or to mimic their functions are hampered, however, by the lack of biosynthetic knowledge of these unique sugars. To elucidate the mechanism by which the sugar deoxygenation is effected, we have initiated a study to explore the biosynthesis of CDP‐ascarylose, a 3,6‐dideoxyhexose found in the lipopolysaccharides of Yersinia pseudotuberculosis, and our initial focus centered on C‐3 deoxygenation catalyzed by E1 and E3. We have now purified the wild‐type enzymes, cloned the corresponding genes (ascC for E1 and ascD for E3), and overexpressed the gene products in Escherichia coli. The purified E3 is a flavoprotein comprising an iron‐sulfur center and E1 is an iron‐sulfur containing, pyridoxamine 5′‐phosphate‐de‐pendent enzyme. Since these iron‐sulfur clusters are well known one‐electron carriers, reactions mediated by E1 and E3 must proceed via a radical mechanism. Recently, EPR analysis of E1/E3 catalysis indicated a potential new redox role for pyridoxamine as a cofactor. These findings make this system unique from two perspectives: E1 is the only coenzyme B6‐dependent catalyst that interacts with a sugar and not with an amino acid, and it is the first example in which coenzyme B6 may facilitate one‐electron redox chemistry. Thus, the unprecedented mechanisms of E1 and E3 distinguish this system as a novel radical deoxygenation with potentially interesting future developments.

Original languageEnglish
Pages (from-to)627-636
Number of pages10
JournalJournal of the Chinese Chemical Society
Issue number4
StatePublished - Aug 1995


  • Ascarylose
  • Deoxysugars
  • Enzyme
  • Iron‐sulfur cluster
  • Mechanism
  • Pyridoxamine
  • Radical

ASJC Scopus subject areas

  • Chemistry (all)


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