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Two aerobic pathways for the formation of unsaturated fatty acids in Pseudomonas aeruginosa
Author(s) -
Zhu Kun,
Choi KyoungHee,
Schweizer Herbert P.,
Rock Charles O.,
Zhang YongMei
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05088.x
Subject(s) - biology , biochemistry , mutant , dehydratase , fatty acid , metabolism , enzyme , unsaturated fatty acid , phospholipid , gene , membrane
Summary The double bond in anaerobic unsaturated fatty acid (UFA) biosynthesis is introduced by the FabA dehydratase/isomerase of the bacterial type II fatty acid biosynthetic pathway. A Δ fabA mutant of Pseudomonas aeruginosa grew aerobically, but required a UFA supplement for anaerobic growth. Wild‐type cells produced 18:1Δ11 as the principal UFA, whereas the Δ fabA strain produced only 16:1Δ9. The double bond in the 16:1Δ9 was introduced after phospholipid formation and was localized in the sn ‐2 position. Two predicted membrane proteins, DesA and DesB , possessed the conserved histidine clusters characteristic of fatty acid desaturases. The Δ fabA Δ desA double mutant required exogenous fatty acids for growth but the Δ fabAdesB double mutant did not. Exogenous stearate was converted to 18:1Δ9 and supported the growth of Δ fabA Δ desA double mutant. A Δ fabA Δ desAdesB triple mutant was unable to desaturate exogenous stearate and was an UFA auxotroph. We detected a 2.5‐fold increase in desA expression in Δ fabA mutants, whereas desB expression was derepressed by the deletion of the gene encoding a transcriptional repressor DesT. These data add two aerobic desaturases to the enzymes used for fatty acid metabolism in proteobacteria: DesA, a 2‐position phospholipid Δ9‐desaturase that supplements the anaerobic FabA pathway, and DesB, an inducible acyl‐CoA Δ9‐desaturase whose expression is repressed by DesT.