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Discovery of Aerobic Mechanisms 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 -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a947
Subject(s) - biochemistry , fatty acid , double bond , strain (injury) , chemistry , mutant , auxotrophy , linoleic acid , unsaturated fatty acid , biology , organic chemistry , gene , anatomy
Unsaturated fatty acids (UFA) are produced anaerobically, or by oxidative desaturation in the presence of oxygen. Anaerobic synthesis introduces the double bond into the growing acyl chain by the FabA dehydratase/isomerase component of the bacterial type II fatty acid biosynthetic pathway. A Δ fabA mutant of Pseudomonas aeruginosa grew without exogenous UFA but was a UFA auxotroph under anaerobic conditions. Wild‐type cells produced C18:1 as the principal UFA, while the Δ fabA strain produced mainly C16:1. Two membrane proteins in P. aeruginosa , DesA and DesB , possessed the characteristic desaturase histidine clusters which are essential for catalysis. No fatty acid compositional changes were found in either Δ desA or Δ des B strains. Δ fabA Δ desA double mutant required UFA for growth but Δ fabA Δ desB double mutant did not. DesA expression rescued Δ fabA Δ desA strain from UFA auxotroph and elevated C16:1 production, indicating that DesA was responsible for C16:1 formation in Δ fabA strain. Acetate pulse‐chase experiments demonstrated that in the Δ fabA strain the double bond in C16:1 was introduced after fatty acid biosynthesis. The C16:1 was located in the sn ‐2 position of phosphatidylethanolamine and the double bond was at the Δ9 position. Stearate supported the growth of Δ fabA Δ desA double mutant, and it was converted to C18:1 9, whereas wild type cell has C18:1 11. The expression of desB was induced by stearate, and repressed by oleate. Thus, P. aeruginosa has both an oxygen‐dependent phospholipid desaturase (DesA) and an acy‐CoA desaturase (DesB). (supported by NIH Grant GM34496)