A stereospecific pathway diverts β-oxidation intermediates to the biosynthesis of rhamnolipid biosurfactants

Chem Biol. 2014 Jan 16;21(1):156-64. doi: 10.1016/j.chembiol.2013.11.010. Epub 2013 Dec 26.


Rhamnolipids are multipurpose surface-active molecules produced by the bacterium Pseudomonas aeruginosa from L-rhamnose and R-3-hydroxyalkanoate (C₁₀±₂) precursors. R-3-hydroxyalkanoate precursor is believed to be synthesized de novo. We demonstrate, however, that β-oxidation is the predominant source of this precursor. Inhibition of β-oxidation sharply decreases rhamnolipids production, even when using a nonfatty acid carbon source (glycerol). Isotope tracing shows that β-oxidation intermediates are direct precursors of rhamnolipids. A mutant-based survey revealed an operon coding for enoyl-CoA hydratases/isomerases (ECH/I), named RhlYZ, implicated in rhamnolipids production via an axial role in 3-hydroxyalkanoate synthesis. In vitro, RhlZ is an R-ECH/I transforming 2-decenoyl-CoA, a β-oxidation intermediate, into R-3-hydroxydecanoyl-CoA, the potential rhamnolipids precursor. Interestingly, polyhydroxyalkanoates share with rhamnolipids the RhlYZ-generated R-3-hydroxyalkanoates pool, as demonstrated by the decrease of polyhydroxyalkanoates upon mutation of rhlYZ and the increase of rhamnolipids in a polyhydroxyalkanoates-defective mutant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Enoyl-CoA Hydratase / antagonists & inhibitors
  • Enoyl-CoA Hydratase / genetics
  • Enoyl-CoA Hydratase / metabolism*
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology
  • Glycolipids / biosynthesis*
  • Glycolipids / chemistry
  • Isomerases / antagonists & inhibitors
  • Isomerases / genetics
  • Isomerases / metabolism*
  • Molecular Structure
  • Oxidation-Reduction
  • Polyhydroxyalkanoates / biosynthesis
  • Polyhydroxyalkanoates / chemistry
  • Pseudomonas aeruginosa / chemistry
  • Pseudomonas aeruginosa / enzymology*
  • Pseudomonas aeruginosa / metabolism
  • Stereoisomerism
  • Structure-Activity Relationship
  • Surface-Active Agents / chemistry
  • Surface-Active Agents / metabolism*


  • Enzyme Inhibitors
  • Glycolipids
  • Polyhydroxyalkanoates
  • Surface-Active Agents
  • rhamnolipid
  • Enoyl-CoA Hydratase
  • Isomerases