Beta -oxidation of unsaturated fatty acids in yeast.
Item
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Title
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Beta -oxidation of unsaturated fatty acids in yeast.
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Identifier
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AAI3292487
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identifier
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3292487
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Creator
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Ntamack, Andre Guillaume.
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Contributor
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Adviser: Horst Schulz
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Date
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2007
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry
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Abstract
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The beta-oxidation of fatty acids to acetyl-CoA is a central energy-yielding pathway in animals, yeast, and bacteria. This study of the beta-oxidation of oleic acid in Saccharomyces cerevisiae was initiated by measuring and comparing the growth of wild-type S. cerevisiae on oleic acid or palmitic acid with the growth of mutants that have either a deletion in the DCI1 gene reported to encode Delta 3,5, Delta2,4-dienoyl-CoA isomerase (dienoyl-CoA isomerase) or in the thioesterase gene (TES1) or in both the DCI1 and TES1 genes. Growth of wild-type yeast and the DCI1 mutant was indistinguishable on either palmitic acid or oleic acid, whereas the TES1 mutant grew slower and to a lower density on oleic acid but not on palmitic acid. 3,5-Tetradecadienoic acid was detected in the growth medium by gas chromatography/mass spectrometry after growth of wild-type cells on oleic acid, but not when palmitic acid was the carbon source. When the TES1 mutant was transformed with a plasmid expressing human dienoyl-CoA isomerase to increase the dienoyl-CoA isomerase activity, the growth defect on oleic acid was partially corrected. The purified product of the DCI1 gene expressed in E.coli did not exhibit dienoyl-CoA isomerase activity. Low levels of dienoyl-CoA isomerase activity were detected in wild-type yeast but also in the DCI1 mutant. However beta-oxidation enzymes in the DCI1 mutant were upregulated and mislocalised to the cytosol. These observations support the conclusion that the DCI1 gene product is not a beta-oxidation enzyme, but rather is involved in protein import into peroxisomes. Hence 3,5-tetradecadienoyl-CoA, an intermediate of oleate beta-oxidation, does not seem to be degraded via the reductase-dependent pathway, which does not operate in yeast. Instead the disposal of 3,5-tetradecadienoyl-CoA is achieved by the thioesterase-dependent pathway that involves hydrolysis of acyl-CoA intermediates, including 3,5-tetradecadienoyl-CoA to the corresponding acids that are excreted into the growth medium.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
