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J. Biol. Chem., Vol. 279, Issue 12, 11042-11050, March 19, 2004

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An Alternative Pathway of Oleate -Oxidation in Escherichia coli Involving the Hydrolysis of a Dead End Intermediate by a Thioesterase^*

Ying Ren, Julia Aguirre, André G. Ntamack, Chinhung Chu, and Horst Schulz

From the Department of Chemistry, City College and Graduate School of the City University of New York, New York, New York 10031

The degradation of 2-trans,5-cis-tetradecadienoyl-CoA, a metabolite of oleic acid, by the purified complex of fatty acid oxidation from Escherichia coli was studied to determine how much of the metabolite is converted to 3,5-cis-tetradecadienoyl-CoA and thereby diverted from the classical, isomerase-dependent pathway of oleate -oxidation. Approximately 10% of the 2,5-intermediate was converted to the 3,5-isomer. When the latter compound was allowed to accumulate, it strongly inhibited the flux through the main pathway. Since ^3,5,^2,4-dienoyl-CoA isomerase was not detected in E. coli cells grown on oleate, the 3,5-intermediate cannot be metabolized via the reductase-dependent pathway. However, it was hydrolyzed by a thioesterase, which was most active with 3,5-cis-tetradecadienoyl-CoA as substrate and which was induced by growth of E. coli on oleate. An analysis of fatty acids present in the medium after growth of E. coli on oleate revealed the presence of 3,5-tetradecadienoate, which was not detected after cells were grown on palmitate or glucose. Altogether, these data prompt the conclusion that oleate is mostly degraded via the classical, isomerase-dependent pathway in E. coli but that a small amount of 2-trans,5-cis-tetradecadienoyl-CoA is diverted from the pathway via conversion to 3,5-cis-tetradecadienoyl-CoA by ³,²-enoyl-CoA isomerase. The 3,5-intermediate, which would strongly inhibit -oxidation if allowed to accumulate, is hydrolyzed, and the resultant 3,5-tetradecadienoate is excreted into the growth medium. This study provides evidence for the novel function of a thioesterase in -oxidation.

Received for publication, September 9, 2003 , and in revised form, January 2, 2004.

^* This work was supported by NHLBI, National Institutes of Health (NIH), U. S. Public Health Service Grant HL30847 and by NIH Grant RR03060 (to Research Centers of Minority Institutions). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Supported by the Halfway to Careers in Medicine and Research Programs of The New York Community Trust.

To whom correspondence should be addressed: Dept. of Chemistry, City College of CUNY, Convent Ave. at 138th St., New York, NY 10031. Tel.: 212-650-8323; Fax: 212-650-8322; E-mail: hoschu{at}sci.ccny.cuny.edu.

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