1
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Soupene E, Kuypers FA. Ligand binding to the ACBD6 protein regulates the acyl-CoA transferase reactions in membranes. J Lipid Res 2015; 56:1961-71. [PMID: 26290611 PMCID: PMC4583085 DOI: 10.1194/jlr.m061937] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 08/18/2015] [Indexed: 12/17/2022] Open
Abstract
The binding determinants of the human acyl-CoA binding domain-containing protein (ACBD) 6 and its function in lipid renewal of membranes were investigated. ACBD6 binds acyl-CoAs of a chain length of 6 to 20 carbons. The stoichiometry of the association could not be fitted to a 1-to-1 model. Saturation of ACBD6 by C16:0-CoA required higher concentration than less abundant acyl-CoAs. In contrast to ACBD1 and ACBD3, ligand binding did not result in the dimerization of ACBD6. The presence of fatty acids affected the binding of C18:1-CoA to ACBD6, dependent on the length, the degree of unsaturation, and the stereoisomeric conformation of their aliphatic chain. ACBD1 and ACBD6 negatively affected the formation of phosphatidylcholine (PC) and phosphatidylethanolamine in the red blood cell membrane. The acylation rate of lysophosphatidylcholine into PC catalyzed by the red cell lysophosphatidylcholine-acyltransferase 1 protein was limited by the transfer of the acyl-CoA substrate from ACBD6 to the acyltransferase enzyme. These findings provide evidence that the binding properties of ACBD6 are adapted to prevent its constant saturation by the very abundant C16:0-CoA and protect membrane systems from the detergent nature of free acyl-CoAs by controlling their release to acyl-CoA-utilizing enzymes.
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Affiliation(s)
- Eric Soupene
- Children’s Hospital Oakland Research Institute, Oakland, CA 94609
| | - Frans A. Kuypers
- Children’s Hospital Oakland Research Institute, Oakland, CA 94609
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2
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Luttgeharm KD, Cahoon EB, Markham JE. A mass spectrometry-based method for the assay of ceramide synthase substrate specificity. Anal Biochem 2015; 478:96-101. [PMID: 25725359 DOI: 10.1016/j.ab.2015.02.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 02/12/2015] [Accepted: 02/17/2015] [Indexed: 01/24/2023]
Abstract
The acyl composition of sphingolipids is determined by the specificity of the enzyme ceramide synthase (EC 2.3.1.24). Ceramide contains a long-chain base (LCB) linked to a variety of fatty acids to produce a lipid class with potentially hundreds of structural variants. An optimized procedure for the assay of ceramide synthase in yeast microsomes is reported that uses mass spectrometry to detect any possible LCB and fatty acid combination synthesized from unlabeled substrates provided in the reaction. The assay requires the delivery of substrates with bovine serum albumin for maximum activity within defined limits of substrate concentration and specific methods to stop the reaction and extract the lipid that avoid the non-enzymatic synthesis of ceramide. The activity of ceramide synthase in yeast microsomes is demonstrated with the four natural LCBs found in yeast along with six saturated and two unsaturated fatty acyl-coenzyme As from 16 to 26 carbons in length. The procedure allows for the determination of substrate specificity and kinetic parameters toward natural substrates for ceramide synthase from potentially any organism.
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Affiliation(s)
- Kyle D Luttgeharm
- Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Edgar B Cahoon
- Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Jennifer E Markham
- Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
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3
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Nagy HM, Paar M, Heier C, Moustafa T, Hofer P, Haemmerle G, Lass A, Zechner R, Oberer M, Zimmermann R. Adipose triglyceride lipase activity is inhibited by long-chain acyl-coenzyme A. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:588-94. [PMID: 24440819 PMCID: PMC3988850 DOI: 10.1016/j.bbalip.2014.01.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 12/20/2013] [Accepted: 01/06/2014] [Indexed: 12/28/2022]
Abstract
Adipose triglyceride lipase (ATGL) is required for efficient mobilization of triglyceride (TG) stores in adipose tissue and non-adipose tissues. Therefore, ATGL strongly determines the availability of fatty acids for metabolic reactions. ATGL activity is regulated by a complex network of lipolytic and anti-lipolytic hormones. These signals control enzyme expression and the interaction of ATGL with the regulatory proteins CGI-58 and G0S2. Up to date, it was unknown whether ATGL activity is also controlled by lipid intermediates generated during lipolysis. Here we show that ATGL activity is inhibited by long-chain acyl-CoAs in a non-competitive manner, similar as previously shown for hormone-sensitive lipase (HSL), the rate-limiting enzyme for diglyceride breakdown in adipose tissue. ATGL activity is only marginally inhibited by medium-chain acyl-CoAs, diglycerides, monoglycerides, and free fatty acids. Immunoprecipitation assays revealed that acyl-CoAs do not disrupt the protein–protein interaction of ATGL and its co-activator CGI-58. Furthermore, inhibition of ATGL is independent of the presence of CGI-58 and occurs directly at the N-terminal patatin-like phospholipase domain of the enzyme. In conclusion, our results suggest that inhibition of the major lipolytic enzymes ATGL and HSL by long-chain acyl-CoAs could represent an effective feedback mechanism controlling lipolysis and protecting cells from lipotoxic concentrations of fatty acids and fatty acid-derived lipid metabolites. Long-chain acyl-CoAs inhibit ATGL in a non-competitive manner. Inhibition occurs at the N-terminal region of ATGL and independent of CGI-58, the co-activator of ATGL. Acyl-CoA mediated inhibition of lipolysis could represent a general feedback mechanism protecting cells from fatty acid overload.
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Affiliation(s)
- Harald M Nagy
- Institute of Molecular Biosciences, University of Graz, Austria
| | - Margret Paar
- Institute of Molecular Biosciences, University of Graz, Austria
| | - Christoph Heier
- Institute of Molecular Biosciences, University of Graz, Austria
| | - Tarek Moustafa
- Institute of Molecular Biosciences, University of Graz, Austria
| | - Peter Hofer
- Institute of Molecular Biosciences, University of Graz, Austria
| | | | - Achim Lass
- Institute of Molecular Biosciences, University of Graz, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Austria
| | - Monika Oberer
- Institute of Molecular Biosciences, University of Graz, Austria
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4
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Hartmann D, Lucks J, Fuchs S, Schiffmann S, Schreiber Y, Ferreirós N, Merkens J, Marschalek R, Geisslinger G, Grösch S. Long chain ceramides and very long chain ceramides have opposite effects on human breast and colon cancer cell growth. Int J Biochem Cell Biol 2012; 44:620-8. [PMID: 22230369 DOI: 10.1016/j.biocel.2011.12.019] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 12/14/2011] [Accepted: 12/22/2011] [Indexed: 01/14/2023]
Abstract
Ceramides are known to be key players in intracellular signaling and are involved in apoptosis, cell senescence, proliferation, cell growth and differentiation. They are synthesized by ceramide synthases (CerS). So far, six different mammalian CerS (CerS1-6) have been described. Recently, we demonstrated that human breast cancer tissue displays increased activity of CerS2, 4, and 6, together with enhanced generation of their products, ceramides C(16:0), C(24:0), and C(24:1). Moreover, these increases were significantly associated with tumor dignity. To clarify the impact of this observation, we manipulated cellular ceramide levels by overexpressing ceramide synthases 2, 4 or 6 in MCF-7 (breast cancer) and HCT-116 (colon cancer) cells, respectively. Overexpression of ceramide synthases 4 and 6 elevated generation of short chain ceramides C(16:0), C(18:0) and C(20:0), while overexpression of ceramide synthase 2 had no effect on ceramide production in vivo, presumably due to limited substrate availability, because external addition of very long chain acyl-CoAs resulted in a significant upregulation of very long chain ceramides. We also demonstrated that upregulation of CerS4 and 6 led to the inhibition of cell proliferation and induction of apoptosis, whereas upregulation of CerS2 increased cell proliferation. On the basis of our data, we propose that a disequilibrium between ceramides of various chain length is crucial for cancer progression, while normal cells require an equilibrium between very long and long chain ceramides for normal physiology.
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Affiliation(s)
- Daniela Hartmann
- Pharmazentrum frankfurt/ZAFES, Institut für Klinische Pharmakologie, Klinikum der Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt/Main, Germany
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5
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Schiffmann S, Hartmann D, Fuchs S, Birod K, Ferreiròs N, Schreiber Y, Zivkovic A, Geisslinger G, Grösch S, Stark H. Inhibitors of specific ceramide synthases. Biochimie 2011; 94:558-65. [PMID: 21945810 DOI: 10.1016/j.biochi.2011.09.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 09/09/2011] [Indexed: 10/17/2022]
Abstract
Ceramide synthases (CerSs) are key enzymes in the biosynthesis of ceramides and display a group of at least six different isoenzymes (CerS1-6). Ceramides itself are bioactive molecules. Ceramides with different N-acyl side chains (C(14:0)-Cer - C(26:0)-Cer) possess distinct roles in cell signaling. Therefore, the selective inhibition of specific CerSs which are responsible for the formation of a specific ceramide holds promise for a number of new clinical treatment strategies, e.g., cancer. Here, we identified four of hitherto unknown functional inhibitors of CerSs derived from the FTY720 (Fingolimod) lead structure and showed their inhibitory effectiveness by two in vitro CerS activity assays. Additionally, we tested the substances in two cell lines (HCT-116 and HeLa) with different ceramide patterns. In summary, the in vitro activity assays revealed out that ST1058 and ST1074 preferentially inhibit CerS2 and CerS4, while ST1072 inhibits most potently CerS4 and CerS6. Importantly, ST1060 inhibits predominately CerS2. First structure-activity relationships and the potential biological impact of these compounds are discussed.
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Affiliation(s)
- Susanne Schiffmann
- Pharmazentrum Frankfurt/ZAFES, Institute of Clinical Pharmacology, Goethe-University Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt/Main, Germany
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6
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Du Z, Araujo P, Stubhaug I, Frøyland L. Unbound DHA causes a high blank value in β‐oxidation assay: a concern for
in vitro
studies. EUR J LIPID SCI TECH 2010. [DOI: 10.1002/ejlt.200900071] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Zhen‐Yu Du
- National Institute of Nutrition and Seafood Research (NIFES), P.O. Box 2029 Nordnes, N‐5817 Bergen, Norway
| | - Pedro Araujo
- National Institute of Nutrition and Seafood Research (NIFES), P.O. Box 2029 Nordnes, N‐5817 Bergen, Norway
| | - Ingunn Stubhaug
- National Institute of Nutrition and Seafood Research (NIFES), P.O. Box 2029 Nordnes, N‐5817 Bergen, Norway
- Present address: Skretting Aquaculture Research Center AS, 1103 Stavanger, Norway
| | - Livar Frøyland
- National Institute of Nutrition and Seafood Research (NIFES), P.O. Box 2029 Nordnes, N‐5817 Bergen, Norway
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7
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Yurchenko OP, Nykiforuk CL, Moloney MM, Ståhl U, Banaś A, Stymne S, Weselake RJ. A 10-kDa acyl-CoA-binding protein (ACBP) from Brassica napus enhances acyl exchange between acyl-CoA and phosphatidylcholine. PLANT BIOTECHNOLOGY JOURNAL 2009; 7:602-10. [PMID: 19702754 DOI: 10.1111/j.1467-7652.2009.00427.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The gene encoding a 10-kDa acyl-CoA-binding protein (ACBP) from Brassica napus was over-expressed in developing seeds of Arabidopsis thaliana. Biochemical analysis of T(2) and T(3) A. thaliana seeds revealed a significant increase in polyunsaturated fatty acids (FAs) (18:2(cisDelta9,12) and 18:3(cisDelta9,12,15)) at the expense of very long monounsaturated FA (20:1(cisDelta11)) and saturated FAs. In vitro assays demonstrated that recombinant B. napus ACBP (rBnACBP) strongly increases the formation of phosphatidylcholine (PC) in the absence of added lysophosphatidylcholine in microsomes from DeltaYOR175c yeast expressing A. thaliana lysophosphatidylcholine acyltransferase (AthLPCAT) cDNA or in microsomes from microspore-derived cell suspension cultures of B. napus L. cv. Jet Neuf. rBnACBP or bovine serum albumin (BSA) were also shown to be crucial for AthLPCAT to catalyse the transfer of acyl group from PC into acyl-CoA in vitro. These data suggest that the cytosolic 10-kDa ACBP has an effect on the equilibrium between metabolically active acyl pools (acyl-CoA and phospholipid pools) involved in FA modifications and triacylglycerol bioassembly in plants. Over-expression of ACBP during seed development may represent a useful biotechnological approach for altering the FA composition of seed oil.
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Affiliation(s)
- Olga P Yurchenko
- Agricultural Lipid Biotechnology Program, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada
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8
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Siloto RMP, Madhavji M, Wiehler WB, Burton TL, Boora PS, Laroche A, Weselake RJ. An N-terminal fragment of mouse DGAT1 binds different acyl-CoAs with varying affinity. Biochem Biophys Res Commun 2008; 373:350-4. [PMID: 18571500 DOI: 10.1016/j.bbrc.2008.06.031] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Accepted: 06/05/2008] [Indexed: 10/21/2022]
Abstract
A histidine-tagged recombinant N-terminal fragment of type-1 mouse liver diacylglycerol acyltransferase (DGAT; EC 2.3.1.20), MmDGAT1(1-95)His6, was expressed in Escherichia coli, and used to investigate possible acyl-CoA-binding properties. Analysis of the purified fragment by MALDI-TOF mass spectrometry revealed a polypeptide with molecular mass of about 11 kDa which was consistent with the calculated molecular mass based on the deduced amino acid sequence. Lipidex-1000 binding assays indicated that MmDGAT1(1-95)His(6) interacted with long chain fatty acyl-CoAs similar to observations on DGAT1 from oilseed rape (Brassica napus). Binding, as a function of acyl-CoA concentration, differed for palmitoyl (16:0), stearoyl (18:0), and erucoyl (cisDelta(13)22:1)-CoA. Binding of stearoyl- or erucoyl-CoA to MmDGAT1(1-95)His(6) as a function of acyl-CoA concentration, however, was sigmoid and displayed positive cooperativity suggesting that MmDGAT1 may be subject to allosteric modulation by acyl-CoAs. An intra-polypeptide segment within the N-terminal region of MmDGAT1 contained remnants of an acyl-CoA-binding signature initially identified in plant DGAT1. The acyl-CoA-binding site in mammalian DGAT1 could represent a potential target for therapeutic interventions for disorders such as type-2 diabetes and obesity.
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Affiliation(s)
- Rodrigo M P Siloto
- Department of Agricultural, Food and Nutritional Science, 4-10 Agriculture/Forestry Centre, University of Alberta, Edmonton, Alta., Canada T6G 2P5
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9
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Weselake RJ, Madhavji M, Szarka SJ, Patterson NA, Wiehler WB, Nykiforuk CL, Burton TL, Boora PS, Mosimann SC, Foroud NA, Thibault BJ, Moloney MM, Laroche A, Furukawa-Stoffer TL. Acyl-CoA-binding and self-associating properties of a recombinant 13.3 kDa N-terminal fragment of diacylglycerol acyltransferase-1 from oilseed rape. BMC BIOCHEMISTRY 2006; 7:24. [PMID: 17192193 PMCID: PMC1764880 DOI: 10.1186/1471-2091-7-24] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Accepted: 12/27/2006] [Indexed: 12/01/2022]
Abstract
Background Diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) catalyzes the acyl-CoA-dependent acylation of sn-1, 2-diacylglycerol to generate triacylglycerol and CoA. The deduced amino acid sequence of cDNAs encoding DGAT1 from plants and mammals exhibit a hydrophilic N-terminal region followed by a number of potential membrane-spanning segments, which is consistent with the membrane-bound nature of this enzyme family. In order to gain insight into the structure/function properties of DGAT1 from Brassica napus (BnDGAT1), we produced and partially characterized a recombinant polyHis-tagged N-terminal fragment of the enzyme, BnDGAT1(1–116)His6, with calculated molecular mass of 13,278 Da. Results BnDGAT1(1–116)His6 was highly purified from bacterial lysate and plate-like monoclinic crystals were grown using this preparation. Lipidex-1000 binding assays and gel electrophoresis indicated that BnDGAT1(1–116)His6 interacts with long chain acyl-CoA. The enzyme fragment displayed enhanced affinity for erucoyl (22:1cisΔ13)-CoA over oleoyl (18:1cisΔ9)-CoA, and the binding process displayed positive cooperativity. Gel filtration chromatography and cross-linking studies indicated that BnDGAT1(1–116)His6 self-associated to form a tetramer. Polyclonal antibodies raised against a peptide of 15 amino acid residues representing a segment of BnDGAT1(1–116)His6 failed to react with protein in microsomal vesicles following treatment with proteinase K, suggesting that the N-terminal fragment of BnDGAT1 was localized to the cytosolic side of the ER. Conclusion Collectively, these results suggest that BnDGAT1 may be allosterically modulated by acyl-CoA through the N-terminal region and that the enzyme self-associates via interactions on the cytosolic side of the ER.
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Affiliation(s)
- Randall J Weselake
- Department of Agricultural, Food and Nutritional Science, 4-10 Agriculture/Forestry Centre, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada
| | - Milan Madhavji
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Steve J Szarka
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
- Present address : SemBioSys Genetics Inc., 110, 2985 23 Avenue N.E., Calgary, AB T1Y 7L3, Canada
| | - Nii A Patterson
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
- Present address: Metabolix Inc., 21 Erie Street, Cambridge, MA 02139, USA
| | - William B Wiehler
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Cory L Nykiforuk
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
- Present address : SemBioSys Genetics Inc., 110, 2985 23 Avenue N.E., Calgary, AB T1Y 7L3, Canada
| | - Tracy L Burton
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Parveen S Boora
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Steven C Mosimann
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Nora A Foroud
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Benjamin J Thibault
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Maurice M Moloney
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
| | - André Laroche
- Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta P.O. Box 3000 Main, Lethbridge, Alberta, T1J 4B1, Canada
| | - Tara L Furukawa-Stoffer
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
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10
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Hollenback D, Bonham L, Law L, Rossnagle E, Romero L, Carew H, Tompkins CK, Leung DW, Singer JW, White T. Substrate specificity of lysophosphatidic acid acyltransferase beta -- evidence from membrane and whole cell assays. J Lipid Res 2005; 47:593-604. [PMID: 16369050 DOI: 10.1194/jlr.m500435-jlr200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Membranes of mammalian cells contain lysophosphatidic acid acyltransferase (LPAAT) activities that catalyze the acylation of sn-1-acyl lysophosphatidic acid (lysoPA) to form phosphatidic acid. As the biological roles and biochemical properties of the six known LPAAT isoforms have yet to be fully elucidated, we have characterized human LPAAT-beta activity using two different assays. In a membrane-based assay, LPAAT-beta used lysoPA and lysophosphatidylmethanol (lysoPM) but not other lysophosphoglycerides as an acyl acceptor, and it preferentially transferred 18:1, 18:0, and 16:0 acyl groups over 12:0, 14:0, 20:0, and 20:4 acyl groups. The fact that lysoPM could traverse cell membranes permitted additional characterization of LPAAT-beta activity in cells: PC-3 and DU145 cells converted exogenously added lysoPM and (14)C-labeled 18:1 into (14)C-labeled phosphatidylmethanol (PM). The rate of PM formation was higher in cells that overexpressed LPAAT-beta and was inhibited by the LPAAT-beta inhibitor CT-32501. In contrast, if lysoPM and (14)C-labeled 20:4 were added to PC-3 or DU145 cells, (14)C-labeled PM was also formed, but the rate was neither higher in cells that overexpressed LPAAT-beta nor inhibited by CT-32501. We propose that LPAAT-beta catalyzes the intracellular transfer of 18:1, 18:0, and 16:0 acyl groups but not 20:4 groups to lysoPA.
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Affiliation(s)
- David Hollenback
- Department of Biochemistry, Cell Therapeutics, Inc., Seattle, WA 98119, USA.
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11
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Luo YS, Nicaud JM, Van Veldhoven PP, Chardot T. The acyl-CoA oxidases from the yeast Yarrowia lipolytica: characterization of Aox2p. Arch Biochem Biophys 2002; 407:32-8. [PMID: 12392712 DOI: 10.1016/s0003-9861(02)00466-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One of the acyl-CoA oxidases from the yeast Yarrowia lipolytica, acyl-CoA oxidase 2 (Aox2p), has been expressed in Escherichia coli as an active, N-terminally tagged (His)(6) fusion protein. The specific activity of the purified enzyme, containing FAD, was 19.7 micromolmin(-1)mg(-1) using myristoyl-CoA as substrate. Using substrates with different chain lengths and different substituents, its kinetic properties were further analyzed. Straight-chain acyl-CoAs, with a chain length of 10-14C, are well oxidized, reflecting the properties of Aox2p as deduced from in vivo studies. Acyl-CoAs containing more than 14C were also desaturated, if their concentration was below 25 microM or if proteins capable of binding these CoA-esters, such as albumin or beta-casein, were added to the assay. These long-chain acyl-CoAs, although poor substrates, acted as competitors for the short- and medium-chain substrates. Compared to palmitoyl-CoA, activity toward hexadecadioyl-CoA, containing a omega-carboxy group, was similar. Taken together, these data suggest that micelles of long-chain acyl-CoAs are able to bind and inhibit Aox2p. The enzyme was also active toward acyl-CoA-esters containing a 2-methyl group, but only the 2S isomer was recognized.
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Affiliation(s)
- Yi Shan Luo
- Laboratoire de Chimie Biologique, INRA INA-PG, Centre de Biotechnologie Agro-Industrielle, Thiverval-Grignon, France
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12
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Demant EJ, Nystrøm BT. Continuous recording of long-chain acyl-coenzyme a synthetase activity using fluorescently labeled bovine serum albumin. Anal Biochem 2001; 295:38-44. [PMID: 11476543 DOI: 10.1006/abio.2001.5181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The fluorescence-based long-chain fatty acid probe BSA-HCA (bovine serum albumin labeled with 7-hydroxycoumarin-4-acetic acid) is shown to respond to binding of long-chain acyl-CoA thioesters by quenching of the 450 nm fluorescence emission. As determined by spectrofluorometric titration, binding affinities for palmitoyl-, stearoyl-, and oleoyl-CoA (Kd = 0.2-0.4 microM) are 5-10 times lower than those for the corresponding nonesterified fatty acids. In the presence of detergent (Chaps, Triton X-100, n-octylglucoside) above the critical micelle concentration, acyl-CoA partitions from BSA-HCA and into the detergent micelles. This allows BSA-HCA to be used as a fluorescent probe for continuous recording of fatty acid concentrations in detergent solution with little interference from acyl-CoA. Using a calibration of the fluorescence signal with fatty acids in the C14 to C20 chain-length range, fatty acid consumption by Pseudomonas fragi and rat liver microsomal acyl-CoA synthetase activities are measured down to 0.05 microM/min with a data sampling rate of 10 points per second. This new method provides a very promising spectrofluorometric approach to the study of acyl-CoA synthetase reaction kinetics at physiologically relevant (nM) aqueous phase concentrations of fatty acid substrates and at a time resolution that cannot be obtained in isotopic sampling or enzyme-coupled assays.
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Affiliation(s)
- E J Demant
- Department of Medical Biochemistry and Genetics, University of Copenhagen, Copenhagen, DK-2200, Denmark.
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13
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Fox SR, Rawsthorne S, Hills MJ. Fatty acid synthesis in pea root plastids is inhibited by the action of long-chain acyl- coenzyme as on metabolite transporters. PLANT PHYSIOLOGY 2001; 126:1259-65. [PMID: 11457976 PMCID: PMC116482 DOI: 10.1104/pp.126.3.1259] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2001] [Revised: 03/14/2001] [Accepted: 04/06/2001] [Indexed: 05/21/2023]
Abstract
The uptake in vitro of glucose (Glc)-6-phosphate (Glc-6-P) into plastids from the roots of 10- to 14-d-old pea (Pisum sativum L. cv Puget) plants was inhibited by oleoyl-coenzyme A (CoA) concentrations in the low micromolar range (1--2 microM). The IC(50) (the concentration of inhibitor that reduces enzyme activity by 50%) for the inhibition of Glc-6-P uptake was approximately 750 nM; inhibition was reversed by recombinant rapeseed (Brassica napus) acyl-CoA binding protein. In the presence of ATP (3 mM) and CoASH (coenzyme A; 0.3 mM), Glc-6-P uptake was inhibited by 60%, due to long-chain acyl-CoA synthesis, presumably from endogenous sources of fatty acids present in the preparations. Addition of oleoyl-CoA (1 microM) decreased carbon flux from Glc-6-P into the synthesis of starch and through the oxidative pentose phosphate (OPP) pathway by up to 73% and 40%, respectively. The incorporation of carbon from Glc-6-P into fatty acids was not detected under any conditions. Oleoyl-CoA inhibited the incorporation of acetate into fatty acids by 67%, a decrease similar to that when ATP was excluded from incubations. The oleoyl-CoA-dependent inhibition of fatty acid synthesis was attributable to a direct inhibition of the adenine nucleotide translocator by oleoyl-CoA, which indirectly reduced fatty acid synthesis by ATP deprivation. The Glc-6-P-dependent stimulation of acetate incorporation into fatty acids was reversed by the addition of oleoyl-CoA.
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Affiliation(s)
- S R Fox
- The Department of Brassica and Oilseeds Research, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom
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14
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Lee H, Kim IH. Thioredoxin-linked lipid hydroperoxide peroxidase activity of human serum albumin in the presence of palmitoyl coenzyme A. Free Radic Biol Med 2001; 30:327-33. [PMID: 11165879 DOI: 10.1016/s0891-5849(00)00483-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Human Serum Albumin (HSA) exerted a significant lipid peroxidase activity with the use of a thiol-reducing equivalent such as dithiothreitol (DTT). Carboxyl group-modified HSA (CM-HSA) showed a 10-fold stronger lipid peroxidase activity (1.6 nmol/min/mg) than that of HSA (0.17 nmol/min/mg). Instead of DTT, thioredoxin (Trx) also supported reducing equivalent to the reduction of lipid hydroperoxide by CM-HSA. Contrast to CM-HSA, HSA did not reduce lipid peroxide with the use of Trx. In the presence of palmitoyl coenzyme A (palmitoyl-CoA) however, HSA used Trx as an electron donor to the reduction of lipid hydroperoxide. The Trx-linked peroxidase activity of HSA sharply increased with elongation in the carbon chain of the acyl moiety of acyl-CoA, showing an optimum activity in the presence of palmitoyl-CoA. Fluorescence study indicates the conformational changes of HSA induced by palmitoyl-CoA. Together, these data suggest that palmitoyl-CoA-bound HSA has a capability to remove lipid peroxide with the use of electrons given by Trx system.
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Affiliation(s)
- H Lee
- Department of Biochemistry, Paichai University, 439-6 Doma-2 Dong Seo-Gu Taejon 302-735, Republic of Korea
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15
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Chao H, Billheimer JT, Kier AB, Schroeder F. Microsomal long chain fatty acyl-CoA transacylation: differential effect of sterol carrier protein-2. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1439:371-83. [PMID: 10498408 DOI: 10.1016/s1388-1981(99)00109-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The recent discovery that sterol carrier protein-2 (SCP-2) binds long chain++ (LCFA-CoA) with high affinity (A. Frolov et al., J. Biol. Chem. 271 (1997) 31878-31884) suggests new possible functions of this protein in LCFA-CoA metabolism. The purpose of the present investigation was to determine whether SCP-2 differentially modulated microsomal LCFA-CoA transacylation to cholesteryl esters, triacylglycerols, and phospholipids in vitro. Microsomal acyl-CoA:cholesterol acyltransferase (ACAT) activity measured with liposomal membrane cholesterol donors depended on substrate LCFA-CoA level, mol% cholesterol in the liposomal membrane, and total amount of liposomal cholesterol. As compared to basal activity without liposomes, microsomal ACAT was inhibited 30-50% in the presence of cholesterol poor (1.4 mol%) liposomes. In contrast, cholesterol rich (>25 mol%) liposomes stimulated ACAT up to 6.4-fold compared to basal activity without liposomes and nearly 10-fold as compared to cholesterol pool (1.4 mol%) liposomes. Increasing oleoyl-CoA reversed the inhibition of microsomal ACAT by cholesterol poor (1.4 mol%) liposomes, but did not further stimulate ACAT in the presence of cholesterol rich (35 mol%) liposomes. In contrast, high (100 microM) oleoyl-CoA inhibited ACAT nearly 3-fold. This inhibition was reversed by LCFA-CoA binding proteins, bovine serum albumin (BSA) and SCP-2. SCP-2 was 10-fold more effective (mole for mole) than BSA in reversing LCFA-CoA inhibited microsomal ACAT. Concomitantly, under conditions in which SCP-2 stimulated ACAT it equally enhanced transacylation of oleoyl-CoA into phospholipids, and 5.2-fold enhanced oleoyl-CoA transacylation to triacylglycerols. In summary, SCP-2 appeared to exert its greatest effects on microsomal transacylation in vitro by reversing LCFA-CoA inhibition of ACAT and by differentially targeting LCFA-CoA to triacylglycerols. These data suggest that the high affinity interaction of SCP-2s with LCFA-CoA may be physiologically important in microsomal transacylation reactions.
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Affiliation(s)
- H Chao
- Department of Pathobiology, Texas A&M University, TVMC, College Station, TX 77843-4467, USA
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16
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Broadway NM, Saggerson ED. Effect of membrane environment on the activity and inhibitability by malonyl-CoA of the carnitine acyltransferase of hepatic microsomal membranes. Biochem J 1997; 322 ( Pt 2):435-40. [PMID: 9065760 PMCID: PMC1218209 DOI: 10.1042/bj3220435] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have investigated the extent to which membrane environment affects the catalytic properties of the malonyl-CoA-sensitive carnitine acyltransferase of liver microsomal membranes. Arrhenius-type plots of activity were linear in the absence and presence of malonyl-CoA (2.5 microM). Sensitivity to malonyl-CoA increased with decreasing assay temperature. Partly purified enzyme displayed an increased K0.5 (substrate concentration supporting half the maximal reaction rate) for myristoyl-CoA and a reduced sensitivity to malonyl-CoA compared with the enzyme in situ in membranes. Reconstitution with liposomes of a range of compositions restored the K0.5 for myristoyl-CoA to values similar to that seen in native membranes. The lipid requirements for restoration of sensitivity to malonyl-CoA were more stringent. When animals were starved for 24 h the specific activity of carnitine acyltransferase in microsomal membrane residues was increased 3.3-fold, whereas sensitivity to malonyl-CoA was decreased to 1/2.8. When enzymes partly purified from fed and starved animals were reconstituted into crude soybean phosphatidylcholine liposomes there was no difference in sensitivity to malonyl-CoA. When partly purified enzyme from fed rats was reconstituted into liposomes prepared from microsomal membrane lipids from fed animals it was 2.2-fold more sensitive to malonyl-CoA than when reconstituted with liposomes prepared from microsomal membrane lipids from starved animals. This suggests that the physiological changes in sensitivity to malonyl-CoA are mediated via changes in membrane lipid composition rather than via modification of the enzyme protein itself. The increased specific actvity of acyltransferase observed on starvation could not be attributed to changes in membrane lipid composition.
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Affiliation(s)
- N M Broadway
- Department of Biochemistry and Molecular Biology, University College London, U.K
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17
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Eccleston VS, Harwood JL. Solubilisation, partial purification and properties of acyl-CoA: glycerol-3-phosphate acyltransferase from avocado (Persea americana) fruit mesocarp. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1257:1-10. [PMID: 7599174 DOI: 10.1016/0005-2760(95)00054-g] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Glycerol-3-phosphate acyltransferase (G3PAT) activity was studied using a microsomal membrane fraction from avocado (Persea americana) mesocarp. G3PAT was shown to be an integral membrane protein, having an active site that appeared to be accessible to the cytoplasmic face of the endoplasmic reticulum, in experiments using limited proteolytic digestion. CHAPS solubilisation (0.25%, w/v) of microsomal G3PAT activity was used as an initial step in purification of this enzyme. Both CHAPS-solubilised and microsomal G3PAT activities were characterised and compared. Affinity chromatography was used to purify microsomal G3PAT for the first time from a plant source. Glycerophosphorylethanolamine coupled to cyanogen bromide-activated Sepharose was used for this purpose. Specific elution of G3PAT by a solution of glycerol-3-phosphate resulted in about 150-fold purification. The significance of the results and the potential usefulness of the purification method for further studies of G3PAT in plants are discussed.
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Affiliation(s)
- V S Eccleston
- Department of Biochemistry, University of Wales College of Cardiff, UK
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18
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Rich GT, Comerford JG, Graham S, Dawson AP. Effects of CoA and acyl-CoA on Ca(2+)-permeability of endoplasmic-reticulum membranes from rat liver. Biochem J 1995; 306 ( Pt 3):703-8. [PMID: 7702563 PMCID: PMC1136578 DOI: 10.1042/bj3060703] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have studied the effects of CoA and palmitoyl-CoA on Ca2+ movements and GTP-dependent vesicle fusion in rat liver microsomes. (1) Inhibition of membrane fusion by CoA depends on esterification of CoA to long-chain acyl-CoA using endogenous non-esterified fatty acids. (2) Binding of long-chain acyl-CoA to microsomal membranes is inhibited by BSA, which also relieves inhibition of membrane fusion. (3) Under conditions where acyl-CoA binding is inhibited, CoA causes increased Ca2+ accumulation, apparently by decreasing the Ca2+ leak rate. (4) Conversely, palmitoyl-CoA, in the presence of BSA, causes Ca2+ efflux. (5) The decrease in Ca(2+)-permeability caused by CoA does not depend on the presence of ATP or GTP, and is irreversible in the short term. (6) Using 14C-labelled CoA we show that CoA derivatives can be formed from endogenous components of microsomal membranes in the absence of ATP. (7) The results are interpreted in terms of a Ca(2+)-permeability which is controlled by CoA and/or long-chain acyl-CoA esters.
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Affiliation(s)
- G T Rich
- School of Biological Sciences, University of East Anglia, Norwich, U.K
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19
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Little D, Weselake R, Pomeroy K, Furukawa-Stoffer T, Bagu J. Solubilization and characterization of diacylglycerol acyltransferase from microspore-derived cultures of oilseed rape. Biochem J 1994; 304 ( Pt 3):951-8. [PMID: 7818502 PMCID: PMC1137425 DOI: 10.1042/bj3040951] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Particulate fractions prepared from microspore-derived (MD) embryos of oilseed rape (Brassica napus L. cv. Reston) and an embryogenic MD cell suspension culture of oilseed rape (B. napus L. cv. Jet Neuf) were used as a source of diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) for enzyme characterization and development of a solubilization procedure. DGAT activity in the 1500-100,000 g fraction from MD embryos was stimulated 4-5-fold by 3 to 4 mg of BSA/ml of reaction mixture. DGAT activity from MD embryos was stimulated 2-3-fold by fluoride salts and 1.4-fold by NaCl, whereas iodide salts caused substantial inhibition of enzyme activity. The effect of the various 1:1 electrolytes on enzyme activity appeared to be related more to their differential effects on solution structure rather than ionic strength. DGAT was solubilized from membranes of MD embryos and the cell suspension culture by about 80 and 50% respectively, using 2 M NaCl in 1% (w/v) octanoyl-N-methyl-glucamide (MEGA-8) (pH 8.0 buffer) at a detergent to protein ratio of 2:1. The specific activity of solubilized DGAT was about 2-fold greater than that of the particulate enzyme. The mechanism of solubilization appeared to be related to the lowering of the critical micellar concentration of MEGA-8 in the presence of NaCl. DGAT, solubilized from MD embryos, eluted with an M(r) of about 2 x 10(6) during gel-filtration chromatography on a Superose 6 column equilibrated in buffer containing 0.1% (w/v) MEGA-8. The solubilized enzyme exhibited optimal activity at pH 7. At concentrations above 2 microM acyl-CoA, the specificity of solubilized DGAT for oleoyl-CoA and palmitoyl-CoA was considerably greater than for stearoyl-CoA.
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Affiliation(s)
- D Little
- Department of Chemistry, University of Lethbridge, Alberta, Canada
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20
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Hirschberg K, Rodger J, Futerman AH. The long-chain sphingoid base of sphingolipids is acylated at the cytosolic surface of the endoplasmic reticulum in rat liver. Biochem J 1993; 290 ( Pt 3):751-7. [PMID: 8457204 PMCID: PMC1132344 DOI: 10.1042/bj2900751] [Citation(s) in RCA: 155] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Ceramide, a key intermediate in sphingolipid metabolism, is synthesized by acylation of sphinganine followed by dehydrogenation of dihydroceramide to ceramide. Using radioactive sphinganine, we have examined the site and topology of dihydroceramide synthesis in well-characterized subcellular fractions from rat liver. [4,5-3H]Sphinganine was introduced as a complex with BSA and was metabolized to [4,5-3H]dihydroceramide upon incubation of rat liver homogenates or microsomes with fatty acyl CoA. Conditions were established in a detergent-free system in which dihydroceramide synthesis was not limited by either substrate availability or by amounts of microsomal protein or reaction time. The distribution of dihydroceramide synthesis was found to exactly parallel that of an endoplasmic reticulum (ER) marker upon subfractionation of microsomes, and no endogenous activity was detected in either purified Golgi apparatus or plasma membrane fractions. Limited protease digestion demonstrated that sphinganine N-acyltransferase is localized at the cytosolic surface of intact ER-derived vesicles. These results are discussed with regard to the subsequent transport of (dihydro)-ceramide from the ER to sites of further metabolism in a pre-Golgi apparatus compartment and in the cis and medial cisternae of the Golgi apparatus.
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Affiliation(s)
- K Hirschberg
- Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel
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21
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Substrate specificities of rat liver peroxisomal acyl-CoA oxidases: palmitoyl-CoA oxidase (inducible acyl-CoA oxidase), pristanoyl-CoA oxidase (non-inducible acyl-CoA oxidase), and trihydroxycoprostanoyl-CoA oxidase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)88666-0] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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22
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Boylan JG, Hamilton JA. Interactions of acyl-coenzyme A with phosphatidylcholine bilayers and serum albumin. Biochemistry 1992; 31:557-67. [PMID: 1731912 DOI: 10.1021/bi00117a037] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Interactions of oleoyl- and octanoyl-coenzyme A (CoA) with phosphatidylcholine (PC) vesicles and bovine serum albumin (BSA) were investigated by NMR spectroscopy. Binding of acyl-CoA to small unilamellar PC vesicles and to BSA was detected by changes in 13C and 31P chemical shifts relative to the chemical shifts for aqueous acyl-CoA. When oleoyl-CoA (less than or equal to 15 mol %) was added to preformed vesicles, the 13C thioester signal (200.1 ppm) was upfield from the signal for micellar oleoyl-CoA (201.7 ppm), suggesting decreased H-bonding (partial dehydration) at the carbonyl group upon binding to the bilayer. When vesicles were prepared by cosonication of oleoyl-CoA and PC, a second peak (199.8 ppm) was seen. The major peak at 200.1 ppm broadened and shifted after addition of Dy(NO3)3 and was not seen after addition of BSA, while the peak at 199.8 ppm was unaffected by either perturbation. Thus, oleoyl-CoA in each bilayer leaflet was distinguished, and transbilayer movement was shown to be slow (t 1/2 greater than or equal to hours). PC vesicles remained intact with less than or equal to 15 mol % oleoyl-CoA, while higher oleoyl-CoA proportions produced mixed micelles. In contrast, 13C spectra revealed rapid exchange (ms) of octanoyl-CoA between the aqueous phase and PC vesicles and a low affinity for the bilayer. Thus, the binding affinity of acyl-CoA for PC bilayers is dependent on the acyl chain length. Oleoyl-CoA in the presence of BSA (1 mol/mol) gave rise to three carbonyl signals at 197.2-203.6 ppm. With 2-5 mol of oleoyl-CoA/BSA, 1-2 additional signals were observed. None of the signals corresponded to unbound oleoyl-CoA. Addition of [13C]carboxyl-enriched oleic acid to oleoyl-CoA/BSA mixtures revealed simultaneous binding of oleic acid and oleoyl-CoA to BSA, with some perturbation of binding interactions. Thus, BSA contains multiple binding sites for oleoyl-CoA and can bind fatty acid and acyl-CoA simultaneously.
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Affiliation(s)
- J G Boylan
- Biophysics Department, Housman Medical Research Center, Boston University School of Medicine, Massachusetts 02118-2394
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23
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Juguelin H, Bessoule JJ, Cassagne C. Interaction of amphiphilic substrates (acyl-CoAs) and their metabolites (free fatty acids) with microsomes from mouse sciatic nerves. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1068:41-51. [PMID: 1892854 DOI: 10.1016/0005-2736(91)90058-g] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have measured the partition of stearoyl-CoA and oleoyl-CoA between an aqueous phase and the microsomes from mouse sciatic nerves. A method of microultracentrifugation was used which allowed us to study separately the aqueous phase and the biological membranes. We observed that the partition is dependent upon the amount of acyl-CoAs and membrane proteins but seems to be independent of time. A theoretical analysis of these data allowed interpretation of the binding and release in terms of acyl-CoA surface density in the vesicles. We have also analyzed the fate of the membrane-bound acyl-CoAs. We show that, whereas the apparent partition does not seem to vary, the hydrolysis of the membrane-bound acyl-CoAs followed by the release of free fatty acids from the membrane leads to a modification of the partition of acyl-CoAs between the membrane and the aqueous phase. We propose that there is a constant partition of the aliphatic chains (acyl-CoAs + free fatty acids).
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Affiliation(s)
- H Juguelin
- Institut de Biochimie Cellulaire et de Neurochimie du CNRS, Université de Bordeaux II, France
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24
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Richards EW, Hamm MW, Otto DA. The effect of palmitoyl-CoA binding to albumin on the apparent kinetic behavior of carnitine palmitoyltransferase I. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1076:23-8. [PMID: 1986792 DOI: 10.1016/0167-4838(91)90215-l] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Substrate saturation plots of carnitine palmitoyltransferase I activity from isolated rat liver mitochondria vs. palmitoyl-CoA concentration in the presence of bovine serum albumin have been reported to yield sigmoidal kinetics. Under identical assay conditions we have confirmed these observations as reflected by nonlinear Lineweaver-Burke plots (1/vi vs. 1/[S]) an average Hill coefficient of napp. = 1.98 +/- 0.09 (Mean +/- S.E. from four separate experiments). For these determinations the enzyme activity was plotted against the total [palmitoyl-CoA] in the presence of 0.13% bovine serum albumin. Utilizing the total [palmitoyl-CoA] to determine the kinetic properties of carnitine palmitoyltransferase I would be valid only if the relationship between total and free [palmitoyl-CoA] was linear, which is not the case as we have previously shown. When carnitine palmitoyltransferase I substrate saturation kinetics were reanalyzed using the previously determined free [palmitoyl-CoA]'s, the plots revealed a shift to standard hyperbolic kinetics. This observation was confirmed by an average Hill coefficient of napp. = 1.04 +/- 0.10 (Mean +/- S.E.) and linear Lineweaver-Burke plots. The double-reciprocal plots from these analyses yielded an average S0.5 of 2.55 +/- 0.82 microM (Mean +/- S.E.) palmitoyl-CoA and Vmax of 19.69 +/- 5.48 nmol/min per mg protein. These studies clearly demonstrate the importance of defining the free [palmitoyl-CoA] when analyzing the kinetics of carnitine palmitoyltransferase I in the presence of bovine serum albumin.
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Affiliation(s)
- E W Richards
- Department of Research, Baptist Medical Centers, Birmingham, AL 35211
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