Alternate routes for the beta-oxidation of unsaturated fatty acids in peroxisomes, mitochondria, and Escherichia coli.
Item
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Title
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Alternate routes for the beta-oxidation of unsaturated fatty acids in peroxisomes, mitochondria, and Escherichia coli.
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Identifier
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AAI9304738
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identifier
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9304738
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Creator
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Smeland, Tor Einar.
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Contributor
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Adviser: Horst Schulz
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Date
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1992
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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 | Biology, Microbiology | Biology, Cell
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Abstract
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Rat liver D-3-hydroxyacyl-CoA dehydratase was purified and found to act in combination with enoyl-CoA hydratase to catalyze the epimerization of 3-hydroxyacyl-CoA. The molecular weight of the dehydratase was estimated to be twice that of its 44 kDa subunit. It catalyzes the reversible dehydration of D-3-hydroxyacyl-CoA to 2-trans-enoyl-CoA, but does not act on 2-cis-enoyl-CoA. Virtually inactive toward crontonyl-CoA, it exhibits high activity with 2-trans-hexenoyl-CoA and acts with decreasing efficiency on all 2-enoyl-CoA's from 2-hexenoyl-CoA to 2-hexadecenoyl-CoA. It is suggested that 2-cis-enoyl-CoA intermediates formed during the beta-oxidation of polyunsaturated fatty acids in peroxisomes are hydrated by enoyl-CoA hydratase to D-3-hydroxyacyl-CoA's, which are epimerized to their L-isomers by the sequential actions of D-3-hydroxyacyl-CoA dehydratase and enoyl-CoA hydratase.;The 3-hydroxyacyl-CoA epimerase activity associated with the multienzyme complex of fatty acid oxidation from E. coli, was studied. The E. coli complex catalyzes the rapid, direct dehydration of D-3-hydroxy-4-trans-decenoyl-CoA to 2-trans,4-trans-decadienoyl-CoA, which is slowly hydrated to L-3-hydroxy-4-trans-decenoyl-CoA. A kinetic analysis of the epimerase and its partial reactions established that epimerization of 3-hydroxyacyl-CoAs occurs via dehydration/hydration. A substrate competition study with D- and L-3-hydroxy-4-trans-decenoyl-CoA suggests that a single active site dehydrates the D- and L-isomers of 3-hydroxyacyl-CoAs.;The metabolism of 5-enoyl-CoAs, formed during the beta-oxidation of unsaturated fatty acids with odd-numbered double bonds, was studied. Metabolites were identified by high performance liquid chromatography. 5-cis-Octenoyl-CoA was dehydrogenated by medium-chain acyl-CoA dehydrogenase (EC 1.3.99.3) to 2-trans,5-cis-octadienoyl-CoA, which was isomerized to 3,5-octadienoyl-CoA either by mitochondrial 3-cis,2-trans-enoyl-CoA isomerase (EC-5.3.3.8) or by peroxisomal trifunctional enzyme. Further isomerization of 3,5-octadienoyl-CoA to 2-trans,4-trans-octadienoyl-CoA in the presence of soluble extracts of rat liver or heart mitochondria was attributed to a novel 3,5-2,4-dienoyl-CoA isomerase. A soluble extract of rat liver mitochondria catalyzed the isomerization of 2-trans,5-cis-octadienoyl-CoA to 2-trans,4-trans-octadienoyl-CoA, which upon addition of NADPH, NAD{dollar}\sp+{dollar}, and CoA was chain shortened. It is concluded that odd-numbered double bonds can be reductively removed during the beta-oxidation of polyunsaturated fatty acids.
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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.
