title: A stereospecific pathway diverts β-oxidation intermediates to the biosynthesis of rhamnolipid biosurfactants.
abstract: 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.
authors.affiliation: INRS-Institut Armand-Frappier, Laval, QC H7V 1B7, Canada.
authors.forename: Ahmad Mohammad
authors.initials: AM
authors.lastname: Abdel-Mawgoud
authors.affiliation: INRS-Institut Armand-Frappier, Laval, QC H7V 1B7, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Lépine
authors.affiliation: INRS-Institut Armand-Frappier, Laval, QC H7V 1B7, Canada. Electronic address: eric.deziel@iaf.inrs.ca.
authors.forename: Eric
authors.initials: E
authors.lastname: Déziel
mesh_terms: D004746:Enoyl-CoA Hydratase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D006017:Glycolipids / Q000096:biosynthesis* / Q000737:chemistry; D007535:Isomerases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013501:Surface-Active Agents / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D006017:Glycolipids; D054813:Polyhydroxyalkanoates; D013501:Surface-Active Agents; C418382:rhamnolipid; D004746:Enoyl-CoA Hydratase; D007535:Isomerases