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Ruan B, Lai PS, Yeh CW, Wilson WK, Pang J, Xu R, Matsuda SPT, Schroepfer GJ. Alternative pathways of sterol synthesis in yeast. Use of C(27) sterol tracers to study aberrant double-bond migrations and evaluate their relative importance. Steroids 2002; 67:1109-19. [PMID: 12441197 DOI: 10.1016/s0039-128x(02)00069-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Yeast produce traces of aberrant sterols by minor alternative pathways, which can become significant when normal metabolism is blocked by inhibitors or mutations. We studied sterols generated in the absence of the delta(8)-delta(7) isomerase (Erg2p) or delta(5) desaturase (Erg3p) by incubating three mutant strains of Saccharomyces cerevisiae with 5 alpha-cholest-8-en-3beta-ol, 8-dehydrocholesterol (delta(5,8) sterol), or isodehydrocholesterol (delta(6,8) sterol), together with the corresponding 3 alpha-3H isotopomer. Nine different incubations gave altogether 16 sterol metabolites, including seven delta(22E) sterols formed by action of the yeast C-22 desaturase (Erg5p). These products were separated by silver-ion high performance liquid chromatography (Ag(+)-HPLC) and identified by gas chromatography-mass spectrometry, nuclear magnetic resonance spectroscopy, and radio-Ag(+)-HPLC. When delta(8)-delta(7) isomerization was blocked, exogenous delta(8) sterol underwent desaturation to delta(5,8), delta(6,8), and delta(8,14) sterols. Formation of delta(5,8) sterol was strongly favored over delta(6,8) sterol, but both pathways are essentially dormant under normal conditions of sterol synthesis. The delta(5,8) sterol was metabolically almost inert except for delta(22) desaturation, whereas the delta(6,8) sterol was readily converted to delta(5,7), delta(5,7,9(11)), and delta(7,9(11)) sterols. The combined results indicate aberrant metabolic pathways similar to those in mammalian systems. However, delta(5,7) sterol undergoes only slight isomerization or desaturation in yeast, an observation that accounts for the lower levels of delta(5,8) and delta(5,7,9(11)) sterols in wild-type yeast compared to Smith-Lemli-Opitz individuals.
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Affiliation(s)
- Benfang Ruan
- Department of Chemistry, Rice University, 6100 Main Street, Houston, TX 77005, USA
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2
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Fujimoto Y, Ohyama K, Nomura K, Hyodo R, Takahashi K, Yamada J, Morisaki M. Biosynthesis of sterols and ecdysteroids in Ajuga hairy roots. Lipids 2000; 35:279-88. [PMID: 10783005 DOI: 10.1007/s11745-000-0524-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Hairy roots of Ajuga reptans var. atropurpurea produce clerosterol, 22-dehydroclerosterol, and cholesterol as sterol constituents, and 20-hydroxyecdysone, cyasterone, isocyasterone, and 29-norcyasterone as ecdysteroid constituents. To better understand the biosynthesis of these steroidal compounds, we carried out feeding studies of variously 2H- and 13C-labeled sterol substrates with Ajuga hairy roots. In this article, we review our studies in this field. Feeding of labeled desmosterols, 24-methylenecholesterol, and 13C2-acetate established the mechanism of the biosynthesis of the two C29-sterols and a newly accumulated codisterol, including the metabolic correlation of C-26 and C-27 methyl groups. In Ajuga hairy roots, 3alpha-, 4alpha-, and 4beta-hydrogens of cholesterol were all retained at their original positions after conversion into 20-hydroxyecdysone, in contrast to the observations in a fern and an insect. Furthermore, the origin of 5beta-H of 20-hydroxyecdysone was found to be C-6 hydrogen of cholesterol exclusively, which is inconsistent with the results in the fern and the insect. These data strongly support the intermediacy of 7-dehydrocholesterol 5alpha,6alpha-epoxide. Moreover, 7-dehydrocholesterol, 3beta-hydroxy-5beta-cholest-7-en-6-one (5beta-ketol), and 3beta,14alpha-dihydroxy-5beta-cholest-7-en-6-one (5beta-ketodiol) were converted into 20-hydroxyecdysone. Thus, the pathway cholesterol-->7-dehydrocholesterol-->7-dehydrocholesterol 5alpha,6alpha-epoxide-->5beta-ketol-->5beta-k etodiol is proposed for the early stages of 20-hydroxyecdysone biosynthesis. 3beta-Hydroxy-5beta-cholestan-6-one was also incorporated into 20-hydroxyecdysone, suggesting that the introduction of a 7-ene function is not necessarily next to cholesterol. C-25 Hydroxylation during 20-hydroxyecdysone biosynthesis was found to proceed with ca. 70% retention and 30% inversion. Finally, clerosterol was shown to be a precursor of cyasterone and isocyasterone.
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Affiliation(s)
- Y Fujimoto
- Department of Chemistry and Materials Science, Tokyo Institute of Technology, Japan.
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3
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Moebius FF, Reiter RJ, Hanner M, Glossmann H. High affinity of sigma 1-binding sites for sterol isomerization inhibitors: evidence for a pharmacological relationship with the yeast sterol C8-C7 isomerase. Br J Pharmacol 1997; 121:1-6. [PMID: 9146879 PMCID: PMC1564641 DOI: 10.1038/sj.bjp.0701079] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. The sigma-drug binding site of guinea-pig liver is carried by a protein which shares significant amino acid sequence similarities with the yeast sterol C8-C7 isomerase (ERG2 protein). Pharmacologically-but not structurally-the sigma 1-site is also related to the emopamil binding protein, the mammalian sterol C8-C7 isomerase. We therefore investigated if sterol C8-C7 isomerase inhibitors are high affinity ligands for the (+)-[3H]-pentazocine labelled sigma 1-binding site. 2. Among the compounds which bound with high affinity to native hepatic and cerebral as well as to yeast expressed sigma 1-binding sites were the agricultural fungicide fenpropimorph (Ki 0.005 nM), the antihypocholesterinaemic drugs triparanol (Ki 7.0 nM), AY-9944 (Ki, 0.46 nM) and MDL28,815 (Ki 0.16 nM), the enantiomers of the ovulation inducer clomiphene (Ki 5.5 and 12 nM, respectively) and the antioestrogene tamoxifen (Ki 26 nM). 3. Except for tamoxifen these affinities are essentially identical with those for the [3H]-ifenprodil labelled sterol C8-C7 isomerase of S. cerevisiae. This demonstrates that sigma 1-binding protein and yeast isomerase are not only structurally but also pharmacologically related. Because of its affiliations with yeast and mammalian sterol isomerases we propose that the sigma 1-binding site is localized on a sterol isomerase related protein, involved in postsqualene sterol biosynthesis.
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MESH Headings
- Animals
- Binding Sites
- Brain/drug effects
- Brain/metabolism
- Calcium Channel Blockers/metabolism
- Clomiphene/metabolism
- Clomiphene/pharmacology
- Estrogen Antagonists/metabolism
- Estrogen Antagonists/pharmacology
- Excitatory Amino Acid Antagonists/metabolism
- Fertility Agents, Female/metabolism
- Fertility Agents, Female/pharmacology
- Fungicides, Industrial/metabolism
- Fungicides, Industrial/toxicity
- Guinea Pigs
- Hypolipidemic Agents/metabolism
- Hypolipidemic Agents/pharmacology
- Isoquinolines/metabolism
- Isoquinolines/pharmacology
- Isotope Labeling
- Microsomes/metabolism
- Microsomes, Liver/drug effects
- Microsomes, Liver/metabolism
- Morpholines/metabolism
- Morpholines/toxicity
- Pentazocine/metabolism
- Piperidines/metabolism
- Receptors, sigma/drug effects
- Receptors, sigma/metabolism
- Saccharomyces cerevisiae/enzymology
- Saccharomyces cerevisiae/metabolism
- Stereoisomerism
- Steroid Isomerases/antagonists & inhibitors
- Steroid Isomerases/metabolism
- Tamoxifen/metabolism
- Tamoxifen/pharmacology
- Triparanol/metabolism
- Triparanol/pharmacology
- Verapamil/analogs & derivatives
- Verapamil/metabolism
- trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride/metabolism
- trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride/pharmacology
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Affiliation(s)
- F F Moebius
- Institut für Biochemische Pharmakologie, Universität Innsbruck, Austria
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4
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Moebius FF, Bermoser K, Reiter RJ, Hanner M, Glossmann H. Yeast sterol C8-C7 isomerase: identification and characterization of a high-affinity binding site for enzyme inhibitors. Biochemistry 1996; 35:16871-8. [PMID: 8988026 DOI: 10.1021/bi961996m] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The yeast gene ERG2 encodes a sterol C8-C7 isomerase and is essential for ergosterol synthesis and cell proliferation. Its striking homology with the so-called sigma1 receptor of guinea pig brain, a polyvalent steroid and drug binding protein, suggested that the yeast sterol C8-C7 isomerase (ERG2) carries a similar high affinity drug binding domain. Indeed the sigma ligands [3H]haloperidol (Kd = 0.3 nM) and [3H]ifenprodil (Kd = 1.4 nM) bound to a single population of sites in ERG2 wild type yeast microsomes (Bmax values of 77 and 61 pmol/mg of protein, respectively), whereas binding activity was absent in strains carrying ERG2 gene mutations or disruptions. [3H]Ifenprodil binding was inhibited by sterol isomerase inhibitors such as fenpropimorph (Ki = 0.05 nM), tridemorph (Ki = 0.09 nM), MDL28,815 (Ki = 0.44 nM), triparanol (Ki = 1.5 nM), and AY-9944 (Ki = 5.8 nM). [3H]Haloperidol specifically photoaffinity-labeled a protein with an apparent molecular weight of 27400, in agreement with the molecular mass of the sterol C8-C7 isomerase (24900 Da). 9E10 c-myc antibodies specifically immunoprecipitated the c-myc tagged protein after [3H]haloperidol photolabeling, unequivocally proving that the drug binding site is localized on the ERG2 gene product. Haloperidol, trifluperidol, and ifenprodil inhibited the growth of Saccharomyces cerevisiae and reduced the ergosterol content of cells grown in their presence. Our results demonstrate that the yeast sterol C8-C7 isomerase has a polyvalent high-affinity drug binding site similar to mammalian sigma receptors and that in yeast sigma ligands inhibit sterol biosynthesis.
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Affiliation(s)
- F F Moebius
- Institut für Biochemische Pharmakologie, Universität Innsbruck, Austria
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Affiliation(s)
- E I Mercer
- Department of Biochemistry, University of Wales, Aberystwyth, Dyfed, U.K
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Keesler GA, Casey WM, Parks LW. Stimulation by heme of steryl ester synthase and aerobic sterol exclusion in the yeast Saccharomyces cerevisiae. Arch Biochem Biophys 1992; 296:474-81. [PMID: 1632640 DOI: 10.1016/0003-9861(92)90600-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Saccharomyces cerevisiae sterol and heme auxotrophs were used to elucidate a role for hemes in sterol esterification. Steryl ester synthase (SES) activity was stimulated on average fourfold in cells supplemented with 50 micrograms/ml delta-aminolevulinic acid (ALA). This stimulation was not dependent on ALA per se, but on the ability of this precursor to effect heme competency. The addition of ALA stimulated SES activity of yeast on either fermentative or respiratory carbon sources. The elevation of SES activity was independent of intracellular free sterol, unsaturated fatty acid, or methionine levels. SES activity increases as the cells enter stationary phase, and this increase is enhanced by heme competency. SES was directly inhibited by the hypocholesterolemic drug lovastatin (mevinolin). The inhibition of SES activity by lovastatin was enhanced in heme-competent cells.
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Affiliation(s)
- G A Keesler
- Department of Microbiology, North Carolina State University, Raleigh 27695-7615
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7
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Abstract
The mechanism of each of the reactions in the post-squalene segment of the fungal and higher plant sterol biosynthetic pathway is outlined. The inhibitors of the enzymes catalyzing the reactions are described and how inhibition is brought about is explained in the areas where it is known.
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Affiliation(s)
- E I Mercer
- Department of Biochemistry, University College of Wales, Aberystwyth, Dyfed, United Kingdom
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8
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Fenner GP, Parks LW. Gas chromatographic analysis of intact steryl esters in wild type Saccharomyces cerevisiae and in an ester accumulating mutant. Lipids 1989; 24:625-9. [PMID: 2674578 DOI: 10.1007/bf02535079] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The steryl ester faction from wild type and mutant strains of the yeast Saccharomyces cerevisiae was analyzed without saponification by a non-polar capillary gas chromatographic column. When expressed as microgram ester/mg dry wt, the total ester fraction remained constant or declined slightly from log to stationary phase in the wild type. In the mutant the decrease was more dramatic. No individual ergosteryl ester species was dominant throughout the culture cycle in the wild type. A compound tentatively identified as zymosteryl palmitate was the most prevalent ester in wild type log phase cells, ergosta-5,7-dienyl palmitate and ergosta-5,7-dienyl palmitoleate were the major esters in stationary cells. In the mutant strain, ergosteryl esters of palmitate, palmitoleate, oleate, and stearate were the major ester components throughout the culture cycle. Like the wild type, however, the mutant showed an increase in the proportion of ergosta-5,7-dienyl esters in the stationary phase of the culture cycle. The data did not indicate a sterol/fatty acid specificity during the culture cycle.
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Affiliation(s)
- G P Fenner
- Department of Microbiology, North Carolina State University, Raleigh 27695
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9
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Popják G, Meenan A, Parish EJ, Nes WD. Inhibition of Cholesterol Synthesis and Cell Growth by 24(R, S),25-Iminolanosterol and Triparanol in Cultured Rat Hepatoma Cells. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83338-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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10
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Abstract
The sterol composition of two ascomycetous fungi, Saccharomyces cerevisiae and Gibberella fujikuroi, was examined by chromatographic (TLC, GLC, and HPLC) and spectral (MS and 1H-NMR) methods. Of notable importance was that both fungi produced cholesterol and a homologous series of long chain fatty alcohols (C22 to C30). In addition to ergosterol two novel sterols, ergosta-5,7, 9(11), 22-tetraenol and ergosterol endoperoxide, were isolated as minor compounds in growth-arrested cultures of yeast and in mycelia of G. fujikuroi. 24-Ethylidenelanosterol was also detected in mycelia of G. fujikuroi. A shift in sterol biosynthesis was observed by treatment with 24 (RS), 25-epiminolanosterol (an inhibitor of the S-adenosylmethionine C-24 transferase) and by monitoring the sterol composition at various stages of development. The results are interpreted to imply that the genes for 24-desalkyl, e.g., cholesterol, and 24-alkyl sterols, e.g., 24 beta- methyl cholesterol and 24-ethyl cholesterol, are distributed (but not always expressed) generally throughout the fungi but the occurrence of one or another compounds is influenced by the fitness (structure and amount) for specific sterols to act functionally during fungal ontogeny; sterol fitness is coordinated with Darwinian selection pressures.
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Affiliation(s)
- W D Nes
- Plant Physiology Research Unit, Russell Research Center, USDA, Athens, GA 30613
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11
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Ceruti M, Balliano G, Viola F, Cattel L, Gerst N, Schuber F. Synthesis and biological activity of azasqualenes, bis-azasqualenes and derivatives. Eur J Med Chem 1987. [DOI: 10.1016/0223-5234(87)90050-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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12
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Sterol Biosynthesis in Fungi, a Target for Broad Spectrum Fungicides. CHEMISTRY OF PLANT PROTECTION 1986. [DOI: 10.1007/978-3-642-69790-6_1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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13
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Rezanka T, Dolezalová L, Vyhnálek O, Novotný C. Effect of clomiphene on the content of sterols and fatty acids in Saccharomyces cerevisiae. Folia Microbiol (Praha) 1985; 30:501-5. [PMID: 3910526 DOI: 10.1007/bf02927613] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
During cultivation of Saccharomyces cerevisiae clomiphene regulates both quantitative and qualitative production of sterols and fatty acids as identified by gas chromatography and mass spectrometry. The content of sterols decreases to 75%, the production of fatty acids is comparable with that in the control. The occurrence of sterols increases; sterols with methyl group in position 4, without double bond in position 22 and with double bond in position 24(25) or 24(28) predominate. Among fatty acids shorter saturated and monoene acids are primarily produced, 2-hydroxy acids practically disappeared.
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14
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Heterotrophic nitrifying bacteria in acid forest soils polluted by atmospheric SO2. Folia Microbiol (Praha) 1985. [DOI: 10.1007/bf02927615] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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15
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Hosokawa G, Patterson GW, Lusby WR. Effects of triarimol, tridermorph and triparanol on sterol biosynthesis in carrot, tobacco and soybean suspension cultures. Lipids 1984. [DOI: 10.1007/bf02537407] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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16
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Pereira R, Holmlund CE, Whittaker N. The effect of AY-9944 on yeast sterol and sterol ester metabolism. Lipids 1983; 18:545-52. [PMID: 6194399 DOI: 10.1007/bf02535395] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The effects of the hypocholesterolemic drug AY-9944 (trans-1,4-bis(2-chlorobenzylaminoethyl)cyclohexane dihydrochloride) at two concentrations (10(-4) M and 5 X 10(-4) M) on the synthesis of sterols and sterol esters by Saccharomyces cerevisiae were investigated. Although growth was not markedly affected by the drug, there was a decrease in the free sterol to sterol ester ratio with increased drug concentration. A concomitant increase in the saturated fatty acids esterified to sterol relative to the unsaturated fatty acids was also noted in response to increased drug concentration. Ergosterol accounted for 94.7% of the free sterol in the control culture and for 87.8% of the 5 X 10(-4) M drug-treated culture, respectively. However, in the sterol ester fraction, the ergosterol content decreased from a value of 45.1% in the control culture to 2.4% in the 5 X 10(-4) M AY-9944 treated culture. The sterol ester fraction simultaneously showed increased levels of the delta 8 sterol, fecosterol, in response to increased drug concentration from a 7.4% control value to 57.4% in the 5 X 10(-4) M drug-treated culture. The accumulation of the delta 8 sterol suggests that the site of action of the drug is probably at the delta 8 to delta 7 isomerase step in the biosynthesis of ergosterol. The fact that ergosterol is retained as the major free sterol suggests a biological advantage to the retention of this particular sterol. In addition, the near normal growth in the presence of the drug, in spite of the occurrence of an altered sterol ester profile, indicates that the composition of the sterol ester fraction is not as critical as the free sterol fraction.
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McCammon MT, Parks LW. Lipid synthesis in inositol-starved Saccharomyces cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 713:86-93. [PMID: 6753941 DOI: 10.1016/0005-2760(82)90170-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Lipid synthesis was analyzed in an inositol-requiring mutant of Saccharomyces cerevisiae (MC13). Both rates and cellular amounts of [U-14C]acetate incorporation into phospholipids, triacylglycerols, free sterols and steryl esters were elevated in an inositol-starved culture compared to the supplemented control at a time when the deprived culture was losing viability (inositol-less death). The rates at a later time were greatly reduced. During the period when de novo lipid synthesis was high in the starved culture, phospholipid turnover and presumed conversion to triacylglycerols was also accelerated; no differences were apparent in the turnover of the sterol fractions between the two cultures. No change in the fractional percent of ergosterol or of the sterol precursors could be attributed to inositol starvation. The synthesis and maintenance of membrane lipids (phospholipids and free sterols) and their coupling in cellular metabolism are discussed in light of these results.
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18
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Taylor F, Parks L. An assessment of the specificity of sterol uptake and esterification in Saccharomyces cerevisiae. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(18)43004-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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19
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Fumagalli R, Bernini F, Galli G, Anastasia M, Fiecchi A. The identification of a novel C27 diene, cholesta-5,8-dien-3 beta-OL, in tissues of rats given AY-9944 (trans-1,4-bis(2-dichlorobenzylaminoethyl)cyclohexane) in pregnancy. Steroids 1980; 35:665-72. [PMID: 6157233 DOI: 10.1016/0039-128x(80)90091-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Treatment of pregnant rats with AY-9944, a drug interfering with the last steps of cholesterol biosynthesis, accumulated cholesterol precursors in brain and liver of newborn animals. Different sterol profiles were found in these organs. Along with cholesterol and cholesta-5,7-dien-3 beta-ol, present in both tissues, liver was found to contain a hitherto unreported sterol, absent in brain. The structure of cholesta-5,8-dien-3 beta-ol was attributed to this compound by mass spectrometric, 1H, and 13C NMR analysis.
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20
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Field RB, Holmlund CE, Whittaker NF. The effects of the hypocholesteremic compound 3 beta-(beta-dimethylaminoethoxy)-androst-5-en-17-one on the sterol and steryl ester composition of Saccharomyces cerevisiae. Lipids 1979; 14:741-7. [PMID: 393929 DOI: 10.1007/bf02533900] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
When yeast was grown in the presence of 10(-4) M 3 beta-(beta-dimethylaminoethoxy)-androst-5-en-17-one (DMAE-DHA), the compound 2,3;22,23-dioxidosqualene (DOS) accumulated. Total free sterol was reduced by about 30%, whereas almost no steryl esters were found. The same drug at lower concentration (3 x 10(-6) M) caused a slight increase in steryl ester production, and a 24% reduction in free sterol content. The marked accumulation of ergostra-5,7,22,24(28)-tetraen-3 beta-ol with 3 x 10(-6) M DMAE-DHA indicated that the C24-28 reductase is especially sensitive to the action of the drug.
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21
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Taylor FR, Parks LW. Metabolic interconversion of free sterols and steryl esters in Saccharomyces cerevisiae. J Bacteriol 1978; 136:531-7. [PMID: 361713 PMCID: PMC218576 DOI: 10.1128/jb.136.2.531-537.1978] [Citation(s) in RCA: 76] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The interconversion of free and esterified sterols was followed radioisotopically with [U-14C]acetate and [methyl-14C]methionine. In pulse-chase experiments, radioactivity first appeared mainly in unesterified sterols in exponential-phase cells. Within one generation time, the label equilibrated between the free and esterified sterol pools and subsequently accumulated in steryl esters in stationary-phase cells. When the sterol pools were prelabeled by growing cells aerobically to the stationary phase and the cells were diluted into unlabeled medium, the prelabeled steryl esters returned to the free sterol form under several conditions. (i) During aerobic growth, the prelabeled sterols decreased from 80% to 45% esters in the early exponential phase and then returned to 80% esters as the culture reached the stationary phase. (ii) Under anaerobic conditions, the percentage of prelabeled steryl esters declined continuously. When growth stopped, only 15% of the sterols remained esterified. (iii) In the presence of an inhibitor of sterol biosynthesis, which causes accumulation of a precursor to ergosterol, prelabeled sterols decreased to 40% steryl esters while the precursor was found preferentially in the esterified form. These results indicate that the bulk of the free sterol and steryl ester pools are freely interconvertible, with the steryl esters serving as a supply of free sterols. Furthermore, there is an active cellular control over what types of sterol are found in the free and esterified sterol pools.
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