Showing papers on "Lanosterol published in 1988"
TL;DR: It appears that ketoconazole inhibits cholesterol elimination as bile acids by blocking 14 alpha-demethylation, which results in effective drainage of sterol nucleus as lanosterols into bile and feces, which is associated with a marked reduction in low density lipoprotein (LDL) cholesterol level probably through activation of hepatic LDL apoB receptors.
237 citations
TL;DR: The (Na+,K+)-ATPase ATP hydrolyzing activity from rabbit kidney medulla basolateral membrane vesicles was studied as a function of the cholesterol content of the basol lateral membranes, and cholesterol was stimulatory and inhibitory at low cholesterol contents and at high cholesterol contents.
Abstract: The (Na+,K+)-ATPase ATP hydrolyzing activity from rabbit kidney medulla basolateral membrane vesicles was studied as a function of the cholesterol content of the basolateral membranes The cholesterol content of the membranes was modified by incubation with phospholipid vesicles When the cholesterol content was increased above that found in the native membrane, the (Na+,K+)-ATPase ATP hydrolyzing activity was inhibited When the cholesterol content was decreased from that found in the native membranes, the (Na+,K+)-ATPase ATP hydrolyzing activity was inhibited Analogous effects were found with the K+-activated phosphatase activity of the same membrane vesicles Therefore, at low cholesterol contents, cholesterol was stimulatory, and at high cholesterol contents, cholesterol was inhibitory The structural specificity of this effect was tested by introducing lanosterol and ergosterol as 50% of the membrane sterol Ergosterol was the least effective at supporting (Na+,K+)-ATPase ATP hydrolyzing activity, while lanosterol was more effective, but still not as effective as cholesterol
150 citations
01 Jan 1988
TL;DR: A biochemical understanding of cytochrome P450 and other cytochromes is important and extensive modification of the N-1 substituents and the screening of newly developed compounds with respect to the selectivity to fungal P450(14DM) with some conventional methods are necessary.
Abstract: Numerous azole compounds have been developed as potent antifungal agents These compounds inhibit the growth of fungi by disturbing membrane and membrane-bound enzyme systems Such disturbance is caused by the depletion of ergosterol and the accumulation of 14-methylsterols such as lanosterol, 24-methylene-24,25-dihydrolanosterol, obtusifoliol, and 14-methylfecosterol in the membrane Ergosterol is synthesized from lanosterol with the 14-methylsterols appearing as intermediates in the metabolic pathway The azole antifungal agents inhibit the 14a-demethylation of methylsterols The 14a-demethylation is a cytochrome P450-dependent reaction, and the cytochrome P450 that catalyzes removal of the 14a-methyl group of 14-methylsterols is believed to be the primary target for azole antifungal agents [for a review, see (101)]
133 citations
TL;DR: The results reveal that the celery cells have two requirements for sterols, one is for relatively large amounts of sterol and may be associated with membrane elaboration and the other essential role, termed ‘trigger’, requires trace amounts of Sterol with a 24α-ethyl side chain such as stigmasterol.
70 citations
TL;DR: Data indicate that the cloned sequence codes for the lanosterol 14α-demethylase cytochrome P450 L1A1 from C. albicans, which is believed to represent two allelic forms of the same gene.
56 citations
TL;DR: Nine mutants of Saccharomyces cerevisiae which are resistant to ketoconazole, have been isolated and characterized and the significance of this second site mutation to the point of inhibitory action of ketoconAZole, that is the P-450-mediated C-14 demethylation of lanosterol, is discussed.
Abstract: Nine mutants of Saccharomyces cerevisiae which are resistant to ketoconazole, have been isolated and characterized. In each case the mutation is nuclear in origin and allelic to a previously described mutation, erg3, which gives rise to a block in the delta 5-6 desaturation step of ergosterol biosynthesis. The significance of this second site mutation to the point of inhibitory action of ketoconazole, that is the P-450-mediated C-14 demethylation of lanosterol, is discussed.
46 citations
01 Nov 1988
TL;DR: The nucleotide sequence of the gene and flanking DNA for the cytochrome P450 lanosterol 14 alpha-demethylase (14DM) from the yeast Candida tropicalis ATCC750 and an open reading frame (ORF) of 528 codons encoding a 60.9-kD protein is identified.
Abstract: We report the nucleotide sequence of the gene and flanking DNA for the cytochrome P450 lanosterol 14α-demethylase (14DM) from the yeast Candida tropicalis ATCC750. An open reading frame (ORF) of 528 codons encoding a 60.9-kD protein is identified. This ORF includes a characteristic heme-binding domain, HR2, common to all P450 proteins. This protein and the 14DM from Saccharomyces cerevisiae share 66.5% identical and 23.1% conservatively replaced amino acids in a 516-amino-acid alignment, and thus are orthologous forms of the P450LIA1 gene. Conversely, C. tropicalis 14DM shares relatively little sequence similarity with P450alk, the predominant P450 protein present when this organism is grown on n-alkanes. Sequence information of these three yeast P450s will be useful for structure–function analyses in the future.
43 citations
TL;DR: Serum cholesterol precursor levels and plant sterol levels were related to parameters of cholesterol metabolism in 22 patients with heterozygous familial hypercholesterolemia, indicating that the higher cholesterol absorption efficiency the higher are the serum plant sterols levels and the lower the precursor sterol contents and the overall cholesterol synthesis.
39 citations
38 citations
TL;DR: The hog-liver microsomal cyclase was purified approximately 140-fold by chromatography on DEAE-cellulose and hydroxylapatite and the partially purified enzyme was inactivated by N-ethylmaleimide, following pseudo-first order kinetics, indicating that a cysteine residue is essential for activity.
35 citations
TL;DR: It is demonstrated that de novo synthesis of cholesterol is not essential for cell growth when cells are cultured in the presence of whole serum, and the inhibition of cholesterol synthesis by antiestrogens mainly affected the lanosterol demethylation step and the C-27 sterol to cholesterol conversion.
TL;DR: The Chinese hamster ovary cell mutant, AR45, was selected for amphotericin B resistance after treatment with the mutagen ethyl methanesulfonate and is characterized as being lanosterol 14 alpha-methyl demethylase-deficient, a cholesterol auxotroph with a deficiency in cholesterol biosynthesis.
TL;DR: In this article, the aziridine function at the terminal and least hindered isopentenoid unit was introduced for geraniol, farnesol, and lanosterol with an excess of iodine azide and lithium aluminum hydride.
TL;DR: The inhibitory activities of these derivatives on cholesterol synthesis are discussed on the basis of the position and stereochemistry of the oxygen functional groups on the sterol nucleus.
Abstract: The effects of oxygenated lanosterol derivatives (1-27, 5μM) including 32-oxygenated lanosterol derivatives on cholesterol biosyntheiss from [24, 25-3H2]-24, 25-dihydrolanosterol (18μM) were tested in 10000×g supernatant (S-10) fraction of rat liver homogenate. Among the derivatives, 7-oxolanost-8-en-3β-ol (7-oxo-DHL), 3β-acetoxylanost-8-en-7-one (7-oxo-DHL-3-OAc), and 7-oxolanosta-5, 8, 11-trien-3β-ol were highly active in depression cholesterol biosynthesis from 24, 25-dyhydrolanosterol. The inhibitory activities of these derivatives on cholesterol synthesis are discussed on the basis of the position and stereochemistry of the oxygen functional groups on the sterol nucleus. The effect of aphidicolin on cholesterol synthesis was also compared with that of 7-oxo-DHL.
TL;DR: There is a need for a new agent that has a much larger safety margin and lacks this toxicity related to changes in steroid hormones, and a new antifungal agent should be highly selective for fungal cytochrome P-450 enzymes.
Abstract: The rising incidence of disseminated fungal infections in compromised patients and the prolonged treatments that are necessary have highlighted the shortcomings of existing antifungal therapies. Amphotericin B is overtly toxic to the kidneys and must be given by a parenteral route, whereas ketoconazole has proved to have some toxicity related to changes in steroid hormones. Griseofulvin, although orally active, is only effective against dermatophytes. Several other antifungal compounds containing azole ring structures have been reported for both plant\"' and potential human u~e'.~-but none has reached the market and has oral activity. The principal point of action of azole antifungal agents appears to be at the level of the cell membrane. It has been postulated that changes in cell membrane sterols may affect the action of membrane-bound enzymes, such as chitin synthase, and that these effects may ultimately slow cell g r ~ w t h . ~ The primary product of sterol metabolism in fungi is ergosterol; the azole antifungal agents inhibit its biosynthesis by interfering at the stage of lanosterol C14-demethylation.6 The enzyme catalyzing this reaction has been shown to be a cytochrome P-450-linked monooxygenase involving the production of formate from atmospheric oxygen.' Cytochrome P-450 is a ubiquitous hemoprotein found throughout the plant and animal kingdoms and is recognized as having an important role in the metabolism of lipids, in xenobiotic degradation in the liver, and in many other reactions? The azole antifungal agents are believed to interact with the heme by virtue of their unhindered lone-pair electrons on the ring nitrogen. There is always the potential for inhibition of important processes such as steroidogenesis in mammals because this interaction may occur with host enzymes. Therefore, a new antifungal agent should be highly selective for fungal cytochrome P-450 enzymes. Ketoconazole, the only orally active antifungal azole drug available for sale, has been reported to have effects on steroid metabolism at doses used clinically.g~'O There is a need for a new agent that has a much larger safety margin and lacks this toxicity. This communication describes the antifungal compound ICI 195,739 (2-( 2,4-difluoropheny1)1-( 3-[(Z)-44 2,2,3,3-tetrafluoropropoxy)styryl]1,2,4-triazol-l-y1)-3-( 1,2,4triazol-l-yl)propan-2-o1), a bistriazole that is orally active and has a wide spectrum
TL;DR: Cholesterol biosynthesis may be topographically heterogeneous and newly synthesized squalene 2,3-oxide resides in a buoyant membrane fraction distinct from markers for the major organelles.
TL;DR: Structurally different polyterpenoids are (at least partially) functionally equivalent and capable of replacing tetrahymanol or sterols and might act as membrane reinforcers in T. pyriformis cells.
TL;DR: A series of novel 32-functionalised lanost-7-en-3-ols (1)–(7) has been synthesised; these compounds are all powerful inhibitors of lanosterol 14α-methyl demethylase, an important enzyme in cholesterol biosynthesis.
Abstract: A series of novel 32-functionalised lanost-7-en-3-ols (1)–(7) has been synthesised; these compounds are all powerful inhibitors of lanosterol 14α-methyl demethylase, an important enzyme in cholesterol biosynthesis.
TL;DR: Tritium labeled parksol was transformed by the sea cucumber Holothuria arenicola into 14α-methyl-5α-cholest-9(11)-en-3β-ol.
TL;DR: Analysis of the sterols indicate that fenpropimorph has, in the sterol-biosynthetic pathway, target enzymes in mammalian cells different from those in the other phyla, and in the fibroblasts its main target seems to be the demethylation of lanosterol.
Abstract: Fenpropimorph (N-[3-(p-t-butylphenyl)-2-methylpropyl]-cis-2,6-dimethylmorpholine), a morpholine fungicide known to be an inhibitor of sterol biosynthesis in fungi and in higher plants, was demonstrated to be an efficient inhibitor of cholesterol biosynthesis in cultured Swiss 3T3 fibroblasts. Treatment of the mammalian cells with fenpropimorph resulted in a dose-dependent inhibition of [14C]acetate incorporation into the C27 sterols [IC50 (concentration causing half-maximal inhibition) = 0.5 microM], which was accompanied by an accumulation of polar sterols and a decrease in cellular hydroxymethylglutaryl-CoA reductase activity. Exposure of the cells to the drug affected cell growth. Analysis of the sterols in the growth-arrested and in the pulse-labelled cells indicate that fenpropimorph has, in the sterol-biosynthetic pathway, target enzymes in mammalian cells different from those in the other phyla. Whereas in plants and fungi fenpropimorph mainly affects sterol isomerases and reductases, in the fibroblasts its main target seems to be the demethylation of lanosterol.
TL;DR: For instance, after 1-2 hours after intragastric administration of ketoconazole, a cytochrome P-450 inhibitor, to rats, there was a 50-60% decrease in the activity of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase.
Abstract: At 1-2 h after intragastric administration of ketoconazole, a cytochrome P-450 inhibitor, to rats, there was a 50-60% decrease in the activity of hepatic 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase. Inhibition reached a maximum at 6-12 h after the drug was given, but after 24 h enzyme activity was stimulated by 60%. The rates of synthesis of hepatic non-saponifiable lipids in vivo showed a similar time-dependent pattern of change. During the first few hours after drug administration, the hepatic cytochrome P-450-dependent metabolism of lanosterol was suppressed in vivo. However, 24 h after treatment, this activity was stimulated, an effect which was also observed by pre-treatment of the rats with the drug for several days. Suppression of hepatic HMG-CoA reductase and lanosterol 14 alpha-demethylase activities was accompanied by a relative increase in the accumulation of labelled polar sterols in the liver in vivo. In the intestine, ketoconazole also resulted in a rapid decline in the rate of synthesis of non-saponifiable lipids and an inhibition of lanosterol 14 alpha-demethylation in vivo. However, in contrast with the liver, there was no stimulation of non-saponifiable lipid synthesis after 24 h.
TL;DR: A facile chemical synthesis of lanost-8-en-3 beta-ol-24-one (24-ketolanosterol) is described, which was found to be a potent inhibitor of 3-hydroxy-3-methylglutaryl CoA reductase activity in cultured mouse L cells.
TL;DR: The metabolism of 4 was inhibited by 7-oxo-24, 25-dihydrolanosterol (6, 7-Oxo-DHL), which is a potent inhibitor of cholesterol biosynthesis from lanosterol or 4, however, the metabolism of 1 was less inhibited by 6 than that of 4.
Abstract: Metabolism of 32-hydroxylated 24, 25-dihydrolanosterols (1-3), including the intermediate of lanosterol and 24, 25-dihydrolanosterol (4, DHL) demethylation, were studied in a reconstituted system consisting of rat liver partially purified cytochrome P-450, which catalyzes lanosterol 14-demethylation (cytochrome P-45014DM), and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P-450 reductase. The reconstituted system converted lanost-8-ene-3β, 32-diol (1) to 4, 4-dimethyl-5α-cholesta-8, 14, dien-3β-ol (5), the 14-dehydroxymethylated product, in the same way as 4. Lanost-7-ene-3β-32-diol (2) and lanost-6-ene-3β, 32-diol (3), the isomers of 1, were not converted to the corresponding 14-dehydroxymethylated products. The apparent Km value of cytochrome P-45014DM for 1 was about 1/6 of that for 4. The metabolism of 4 was inhibited by 7-oxo-24, 25-dihydrolanosterol (6, 7-oxo-DHL), which is a potent inhibitor of cholesterol biosynthesis from lanosterol or 4. However, the metabolism of 1 was less inhibited by 6 than that of 4.
TL;DR: 3-Hydroxy-3-methylglutaryl-CoA reductase activity, as well as acetate and mevalonate incorporation into nonsaponifiable lipids, was inhibited by the presence of these compounds; this confirms the physiological function of polar steroids in the regulation of cholesterogenesisin vivo.
Abstract: The incorporation of mevalonate into nonsaponifiable lipids by chick liverin vivo strongly increased between 1–18 days after hatching. Cholesterol feeding (2%) inhibited this. Synthesis of cholesterol was strongly inhibited, whereas the intermediates isolated by TLC accumulated. Most of the polar nonsaponifiable lipids that accumulated in liver 90 minutes after mevalonate administration to 18-day-old cholesterol-fed chicks were identified as lanosterol derivative. 3-Hydroxy-3-methylglutaryl-CoA reductase activity, as well as acetate and mevalonate incorporation into nonsaponifiable lipids, was inhibited by the presence of these compounds. To our knowledge, this is the first report of such inhibition; this confirms the physiological function of polar steroids in the regulation of cholesterogenesisin vivo.
TL;DR: An important step in the biosynthesis of the fungal membrane is the cytochrome P450-mediated 14-demethylation of lanosterol to give, after several more steps, ergosterol, and the synthesis of 14-imidazolylmethyl-lanost-8-ene-3-ol was set out.
Abstract: An important step in the biosynthesis of the fungal membrane is the cytochrome P450-mediated 14-demethylation of lanosterol to give, after several more steps, ergosterol. Studies have shown that the imidazole and triazole antifungals inhibit this enzyme because of the binding of the heterocyclic nitrogen atom (N-3 of imidazole and N-4 of triazole) to the protoheme iron atom. This results in the exclusion of oxygen that would normally take part in the reaction.' It is further thought that the nonheterocyclic portion of the antifungal molecule binds to the lipophilic sites of cytochrome P-450.' Because the target of the enzyme is the 14-methyl position of lanosterol, a logical inhibitor would be lanosterol with a heme-binding component (imidazole) at the 14methyl position. Therefore we set out to synthesize 14-imidazolylmethyl-lanost-8-ene-3-ol. Typical methods of introducing a I-alkylimidazole group involve the nucleophilic displacement of alkyl halides or alkyl sulfonates with imidazole. Perhaps a 1Cmethyltosylate or halide could be prepared from the known 14-hydroxymethyl-lanosterol'; however, displacement with a nucleophile, such as an imidazole, adjacent to this neopentyl center could prove extremely difficult. For this reason, we chose to intoduce an amine at the 14-methyl position and to build up the imidazole ring. Our strategy utilized D. H. R. Barton's photolysis of 3&acetoxy-lanost-7a-nitrite (1) to obtain the oxime (2).* Treatment of the oxime with either LAH, LAH-AlCl,, or Red-A1 failed to give the desired 14-aminomethyl compound. Hydrogenation using Pt catalysis with 1.1 equivalents of perchloric acid, however, gave the desired compound in 25% yield. This low yield prompted us to investigate the reduction of the 14-nitrile (3) obtained by dehydration of 2 with Ac,O/pyridine. LAH reduction of the 14-nitrile (3) gave the expected aldehyde after aqueous workup? Even under forced conditions of excess LAH and higher temperatures, no aminomethyl compound was detected. Treatment with 1: 1 LAH:AICl,, however, gave the desired aminomethyl
TL;DR: The incorporation of squalene, lanosterol, dehydroxydemethoxyviridin and demethoxyviidin into viridiol by the fungus, Gliocladium deliquescens, is described.
TL;DR: Incubation of CHO-K1 cells in lipid-deficient medium containing lanosterol for 4 days was associated with a profound change in cellular sterol composition as reflected by a marked accumulation of lanosterols and 24,25-dihydrolanosterol and a striking elongation of the cells.
TL;DR: The sterol composition can regulate specific biochemical processes in the membrane and can be considered as a factor that plays a role in the responsiveness of HL-60 cells to TPA.
Abstract: We have examined the sterol composition and metabolism of promyelocytic leukaemia cell lines (HL-60) after treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA). A variant cell line (Blast II cells) which is resistant to TPA was used as control. Analysis of the sterols of TPA-sensitive cells radiolabelled with [3H]leucine, [14C]acetate or [14C]pyruvate showed a high incorporation into cholesterol and a low incorporation in lanosterol + dihydrolanosterol. The inverse relationship was observed in TPA-resistant cells. Experiments with other cellular variants representing TPA-sensitive and TPA-resistant classes gave similar results. Analysis of the cellular sterol composition by gas chromatography confirmed that TPA-resistant cells are particularly rich in lanosterol/dihydrolanosterol. TPA treatment enhanced the incorporation of [14C]pyruvate into the sterol fraction of both cell types. This was accompanied by an alteration of incorporation into several lipids, particularly phospholipids. Pulse-chase studies with [14C]acetate revealed that TPA induced the release of radioactive lipids into the medium from HL-60 and Blast II cells. However this treatment released phospholipids from the TPA-sensitive cells and sterols and fatty acids from the TPA-resistant cells. We conclude that the sterol composition can regulate specific biochemical processes in the membrane and can be considered as a factor that plays a role in the responsiveness of HL-60 cells to TPA.
TL;DR: Results in this paper demonstrate for the first time the accumulation of a fraction of nonsaponifiable lipid(s) identified as lanosterol derivatives and cholesterol precursors formed by kidneys from [5-14C]mevalonate in experiments carried out in vivo, as well as their evolution during postnatal period.
Abstract: The mevalonate incorporation in vivo into total nonsaponifiable lipids by chick kidneys drastically increased after hatching, reaching similar levels to those previously observed in liver. Cholesterol was the major sterol formed from mevalonate from 11 days onward, while a fraction of polar nonsaponifiable lipid(s) was observed as the major compound(s) synthesized at 5-8 days. Relative percentages of squalene, squalene oxide(s) and lanosterol synthesized from mevalonate also increased between 11-18 days after hatching. Results in this paper demonstrate for the first time the accumulation of a fraction of nonsaponifiable lipid(s) identified as lanosterol derivatives and cholesterol precursors formed by kidneys from [5-14C]mevalonate in experiments carried out in vivo, as well as their evolution during postnatal period.