Mitochondrial metabolism of 3-mercaptopropionic acid; aspects of the beta-oxidation of unsaturated fatty acids; steady-state kinetics of coupled enzyme reactions.
Item
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Title
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Mitochondrial metabolism of 3-mercaptopropionic acid; aspects of the beta-oxidation of unsaturated fatty acids; steady-state kinetics of coupled enzyme reactions.
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Identifier
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AAI8801698
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identifier
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8801698
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Creator
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Cuebas, Dean Anthony.
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Contributor
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Adviser: Horst Schulz
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Date
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1987
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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 metabolism of 3-mercaptopropionic acid in mitochondria was studied by use of purified mitochondrial enzymes and rat heart mitochondria. Metabolites of 3-mercaptopropionic acid were separated by high performance liquid chromatography and identified by comparing them with chemically synthesized derivatives of 3-mercaptopropionic acid. The hydrolysis of S-acyl-3-mercaptopropionyl-CoA thioesters proceeds more rapidly than the hydrolysis of fatty acyl-CoA thioesters of comparable chain lengths. Free CoASH is also regenerated from S-acetyl-3-mercaptopropionyl-CoA and more rapidly from 3-mercaptopropionyl-CoA as a result of their reactions with carnitine catalyzed by carnitine acetyltransferase. These findings lead to the suggestion that the major mitochondrial CoA-containing metabolites of 3-mercaptopropionic acid are S-acyl-3-mercaptopropionyl-CoA thioesters.;3-Mercaptopropionyl-CoA and three of its S-acyl derivatives, all of which are likely mitochondrial metabolites of 3-mercaptopropionic acid, were tested for their capacity to inhibit the individual enzymes of {dollar}\beta{dollar}-oxidation. 3-Mercaptopropionyl-CoA inhibits only acyl-CoA dehydrogenase, whereas S-myristoyl-3-mercaptopropionyl-CoA inhibits reversibly several {dollar}\beta{dollar}-oxidation enzymes. All observations together lead to the suggestion that the inhibition of {dollar}\beta{dollar}-oxidation by 3-mercaptopropionic acid in coupled rat heart mitochondria is most likely a consequence of the reversible inhibition of acyl-CoA dehydrogenase by long-chain S-acyl-3-mercaptopropionyl-CoA thioesters and possibly by 3-mercaptopropionyl-CoA.;A collaborative investigation of the metabolism of 2,4-decadienoyl-CoA, a presumed metabolite in the oxidation of linoleic acid, necessitated the synthesis of various geometric isomers of 2,4-decadienoic acid and their respective CoA derivatives. Additionally, geometrically and optically pure 3-hydroxy-4-decenoic acids and their CoA thioesters were prepared. The characterization of these materials is presented, as well the comparisons of the electronic spectra of three of the four possible geometric isomers of 2,4-decadienoyl-CoA. The equilibrium constant of the 3-hydroxyacyl-CoA dehydrogenase catalyzed oxidation of L-3-hydroxy-4-trans-decenoyl-CoA was determined and found to be 1.1 {dollar}\times{dollar} 10{dollar}\sp{lcub}-8{rcub}{dollar} M, which is significantly higher than the equilibrium constant that had been previously determined for saturated 3-hydroxyacyl-CoA's.;A mathematical analysis of the steady state kinetics of coupled enzyme reactions is presented, where the primary reaction is thermodynamically very unfavored. The derivation of several equations that take into account high concentrations of primary and coupling enzymes is presented, as well as an analysis of the error associated with the use of simple rate equations that do not take into account the binding of substrates due to high enzyme concentrations. (Abstract shortened with permission of author.).
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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.
