Studies on fatty acid oxidation in rat brain and Escherichia coli.
Item
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Title
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Studies on fatty acid oxidation in rat brain and Escherichia coli.
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Identifier
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AAI9130322
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identifier
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9130322
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Creator
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He, Xue-ying.
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Contributor
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Horst Schulz
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Date
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1991
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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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In an attempt to clarify why the brain oxidizes fatty acids poorly or not at all, the activities of {dollar}\beta{dollar}-oxidation enzymes present in rat brain and rat heart mitochondria were measured and compared with each other. The specific activities of all but one brain enzyme are between 4% and 5% of those observed in heart mitochondria. The exception is 3-ketoacyl-CoA thiolase (EC 2.3.1.16) whose specific activity in brain mitochondria is 125-times lower than in heart mitochondria. The rate of fatty acid oxidation in brain mitochondria, estimated on the basis of palmitoylcarnitine-supported respiration and (1-{dollar}\sp{14}{dollar}C) palmitoyl-carnitine degradation to be less than 0.5 nmol/min/mg of protein. Since the reactions catalyzed by carnitine palmitoyltransferase (EC 2.3.1.21) and acyl-CoA synthetase (EC 6.2.1.3) do not seem to restrict fatty acid oxidation in brain, it is concluded that the oxidation of fatty acids in rat brain is limited by the activity of the mitochondrial 3-ketoacyl-CoA thiolase.;In Escherichia coli, a multienzyme complex of fatty acid oxidation exhibiting five different enzymatic activities consists of two large a-subunits and two small {dollar}\beta{dollar}-subunits that are encoded by the fadBA operon. The operon's structure and organization were revealed by sequencing a 5.2-kb DNA (PstI-SalI) fragment located at 87 min on the E. coli chromosome. The direction of transcription of this operon was found to be from fadB to fadA. The transcription start site of the fadBA operon was located 42 nucleotides upstream of the initiator codon of the fadB gene by primer extension analysis, and the location of the promoter of the fadBA operon was thus defined. The 3-ketoacyl-CoA thiolase {dollar}\beta{dollar}-subunit encoded by the fadA gene, is composed of 387 amino acid residues and has a calculated molecular weight 40,876. The large {dollar}\alpha{dollar}-subunit, coded for the fadB gene, a multifunctional protein is composed of 729 amino acid residues and has a calculated Mr of 79,593. Sequence analysis suggest that the functional domains of the multifunctional protein are arranged in the order:enoyl-CoA hydratase:L-3-hydroxyacyl-CoA dehydrogenase:{dollar}\Delta\sp3{dollar}-cis-{dollar}\Delta\sp2{dollar}-trans-enoyl-CoA isomerase.
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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.
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Program
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Biochemistry
