A novel paradigm of fatty acid beta-oxidation exemplified by the thioesterase-dependent partial degradation of conjugated linoleic acid that fully supports growth of Escherichia coli.
An alternative pathway of beta-oxidation for unsaturated fatty acids was studied in Escherichia coli. 9- cis,11- trans-Octadecadienoic acid (conjugated linoleic acid), a potential substrate of this pathway, was shown to support growth of E. coli in the absence of any other carbon source. The identification of 3,5-dodecadienoic acid in the growth medium revealed the partial beta-oxidation of conjugated linoleic acid to 3,5-dodecadienoyl-CoA, which was hydrolyzed to 3,5-dodecadienoic acid and released from cells. The involvement of acyl-CoA thioesterases in this process was evaluated by determining the substrate specificity of thioesterase II and comparing it with that of a novel thioesterase (thioesterase III) and by assessing mutant strains devoid of one or both of these thioesterases for growth on conjugated linoleic acid. Both thioesterases were highly active with 3,5-dodecadienoyl-CoA as substrate. A deficiency of either thioesterase decreased the growth rate of cells on conjugated linoleic acid but not on palmitic acid. The absence of both thioesterases reduced the cellular growth in a cumulative manner but did not abolish it. It is concluded that thioesterases II and III and at least one other thioesterase function in the partial degradation of conjugated linoleic acid via the thioesterase-dependent pathway of beta-oxidation, which provides all energy and carbon precursors required for the growth of E. coli.
Nie
Lina
L
Department of Chemistry, City College and Graduate School of the City University of New York, New York, New York 10031, USA.
Ren
Ying
Y
Janakiraman
Anuradha
A
Smith
Stuart
S
Schulz
Horst
H
D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism*; D044243:Linoleic Acids, Conjugated / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D050356:Lipid Metabolism / Q000187:drug effects / Q000502:physiology; D009154:Mutation; D010084:Oxidation-Reduction / Q000187:drug effects; D019308:Palmitic Acid / Q000378:metabolism / Q000494:pharmacology; D013869:Thiolester Hydrolases / Q000235:genetics / Q000378:metabolism*
D029968:Escherichia coli Proteins; D044243:Linoleic Acids, Conjugated; C046938:9,11-linoleic acid; D019308:Palmitic Acid; D064429:Fatty Acid Synthases; D013869:Thiolester Hydrolases; C022738:thioesterase II