Evidence for the essential function of 2,4-dienoyl-coenzyme A reductase in the beta-oxidation of unsaturated fatty acids in vivo. Isolation and characterization of an Escherichia coli mutant with a defective 2,4-dienoyl-coenzyme A reductase.
For the purpose of assessing in vivo the importance of 2,4-dienoyl-CoA reductase (EC 1.3.1.34) in the beta-oxidation of unsaturated fatty acids, reductase mutants of Escherichia coli were isolated by selecting cells that were able to grow on oleate but not on petroselinic acid (6-cis-octadecenoic acid). One mutant (fadH) exhibited 12% of the 2,4-dienoyl-CoA reductase activity present in the parental strain with other beta-oxidation enzymes being essentially unaffected. Antireductase antibodies were used to show that the mutant contains a fadH gene product at a level similar to that observed in the parental strain. Thus, the mutation seems to have resulted in the synthesis of a fadH gene product with lower specific activity. The mutation was mapped in the 71-75-min region of the E. coli chromosome where no other gene for beta-oxidation enzymes has so far been located. Complementation of the mutation by F'141, which carries the 67-75.5-min region of the E. coli genome, resulted in an increase in the 2,4-dienoyl-CoA reductase activity to 80% of the level found in the parental strain. Measurements of respiration with petroselinic acid as the substrate showed rates to be linearly dependent on the 2,4-dienoyl-CoA reductase activity up to levels found in wild-type E. coli. 2,4-Dienoyl-CoA reductase, like other enzymes of beta-oxidation, was induced when E. coli was grown on a long chain fatty acid as the sole carbon source. It is concluded that 2,4-dienoyl-CoA reductase is required in vivo for the beta-oxidation of unsaturated fatty acids with double bonds extending from even-numbered carbon atoms.
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Department of Chemistry, City College of the City University of New York, New York 10031.
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Schulz
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D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D005779:Immunodiffusion; D007700:Kinetics; D008970:Molecular Weight; D009154:Mutation; D010084:Oxidation-Reduction; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010101:Oxygen Consumption; D013379:Substrate Specificity
D005231:Fatty Acids, Unsaturated; D044943:Fatty Acid Desaturases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C100153:2,4-dienoyl-CoA reductase