Showing papers on "Lanosterol published in 1987"
TL;DR: Observations suggest that the N-1 substituent of an azole antifungal agent regulates the mobility of the molecule in the heme crevice of ferrous P-45014DM and determines the inhibitory effect of the compound.
221 citations
01 Dec 1987
TL;DR: In this article, the structural gene and flanking regions for lanosterol 14 alpha-demethylase (14DM) from Saccharomyces cerevisiae were sequenced and compared with those of eight other eukaryotic P450s.
Abstract: We have sequenced the structural gene and flanking regions for lanosterol 14 alpha-demethylase (14DM) from Saccharomyces cerevisiae. An open reading frame of 530 codons encodes a 60.7-kDa protein. When this gene is disrupted by integrative transformation, the resulting strain requires ergosterol and, as expected, grows only in the absence of oxygen. The deduced amino acid sequence of 14DM includes a hydrophobic segment near the amino terminus which may be a transmembrane domain. The deduced sequence has been compared with those of eight other eukaryotic P450s, each from a different family within the P450 superfamily. These comparisons indicate that this yeast gene is the first member of a new P450 family, P450LI. The P450, designated P450LIA1, is more closely related to mammalian P450s than to the bacterial P450cam. In fact, both the yeast P450 and several mammalian P450s have equivalent alignment scores when each is compared with the bovine P450scc. Matrix comparisons of the amino acid sequence of this P450 with those of mammalian P450s reveal three conserved regions. The DNA region 5' to the structural 14DM gene includes poly(dA:dT) sequences and a repeating hexamer sequence.
178 citations
TL;DR: Different biochemical targets for the antifungals of use in candidosis are discussed in this paper, which include the allylamines and the fluorinated pyrimidine, flucytosine.
Abstract: The past years have seen a continuous effort toward the synthesis of new antifungal agents. Most of them belong to the N-substituted imidazoles and triazoles. Another interesting series of antifungals are the allylamines. Biochemically, both the azole derivatives and the allylamines belong to the class of ergosterol biosynthesis inhibitors and thus differ from the polyene macrolide antibiotics. Indeed, it is now believed that the antifungal action of the polyenes, nystatin and amphotericin B, is due to a direct interaction with ergosterol itself. A more detailed analysis of the ergosterol biosynthesis inhibitors revealed that ergosterol depletion is the consequence of the interaction of the azole derivatives, e.g., miconazole, ketoconazole, and itraconazole, with the cytochrome P-450 involved in the 14 alpha-demethylation of lanosterol. Both the accumulation of 14 alpha-methylsterols and the concomitant decreased ergosterol content affect the membranes and membrane-bound enzymes of yeast and fungi. The allylamines seem to act by inhibition of the squalene epoxidase resulting in ergosterol depletion and accumulation of squalene. The target for the fluorinated pyrimidine, flucytosine, is completely different. Its antifungal properties may result from its conversion to 5-fluorouracil. The latter is then phosphorylated and incorporated into RNA, thus disrupting the protein synthesis in the yeast cell. These different biochemical targets for the antifungals of use in candidosis are discussed in this paper.
150 citations
TL;DR: It is suggested that the altered membrane sterol pattern provides a common basis for the double resistance by preventing polyene binding and reducing azole permeability.
Abstract: Candida albicans 6.4, which is resistant to both polyene and azole groups of antifungal antibiotics, has a larger lipid content and lower polar lipid to neutral lipid ratio compared with other strains that are sensitive or resistant only to azoles. C. albicans 6.4 contains a relatively greater proportion of triacylglycerol in its neutral lipid in the exponential phase of batch culture compared with other strains, but, unlike them, does not accumulate triacylglycerols or any other stored lipid in the stationary phase. Like other strains, in C. albicans 6.4 the major phospholipids are phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol, but sphingomyelin is absent; the major fatty acids are palmitic, palmitoleic, oleic and linoleic acids. In common with other C. albicans strains, strain 6.4 contains non-specific (lyso)phospholipase activity. The main distinctive feature of the lipid composition of C. albicans 6.4 is the absence of ergosterol, which is replaced by methylated sterol; mainly lanosterol, 24-methylene-24,25-dihydrolanosterol and 4-methylergostadiene-3-ol. It is suggested that the altered membrane sterol pattern provides a common basis for the double resistance by preventing polyene binding and reducing azole permeability.
76 citations
TL;DR: It is shown that cycloartenol, the sterol precursor in plants and algae, is also the sterols precursor in Naegleria species, and that these amoebae, like A. polyphaga, are related by some biosynthetic pathways to photosynthetic phyla.
Abstract: The sterols and sterol precursors of two amoebae of the genus Naegleria, Naegleria lovaniensis and Naegleria gruberi were investigated. Cycloartenol, the sterol precursor in photosynthetic organisms, is present in both amoebae. In N. lovaniesis, it is accompanied by lanosterol and parkeol, as well as by the 24,25-dihydro derivatives of these triterpenes. One of the most striking features of these amoebae is the accumulation of 4 alpha-methylsterols which are present in similar amounts as those of 4,4-desmethylsterols (3-5 mg/g, dry weight). 4 alpha-Methylergosta-7,22-dienol was identified as a new compound. Ergosterol was the major 4,4-desmethylsterol, accompanied by small amounts of C27 and other C28 sterols. Treatment of N. lovaniensis with fenpropimorph modified the sterol pattern of this amoeba and inhibited its growth. This fungicide, known to inhibit steps of sterol biosynthesis in fungi and plants, induced the disappearance of 4 alpha-methyl-delta 7-sterols and the appearance of the unusual delta 6,8,22-ergostatrienol as in A. polyphaga. These results might be explained by a partial inhibition of the delta 8----delta 7 isomerase, the small amounts of delta 7-sterols formed being converted into ergosterol which is still present in fenpropimorph-exposed cells. De novo sterol biosynthesis in N. lovaniensis was shown by incorporation of [1-14C]acetate into sterols and sterol precursors, especially cycloartenol. Lanosterol and parkeol were not significantly labelled. Furthermore, [3-3H]squalene epoxide was efficiently cyclized by a cell-free system of this amoeba into cycloartenol, and again no significant radioactivity was detected in lanosterol and parkeol. This shows that cycloartenol, the sterol precursor in plants and algae, is also the sterol precursor in Naegleria species, and that these amoebae, like A. polyphaga, are related by some biosynthetic pathways to photosynthetic phyla. Lanosterol, the sterol precursor in non-photosynthetic phyla (animal and fungi) and parkeol are more likely dead-ends of this biosynthetic pathway. The peculiar phylogenetic position of these protozoa was further emphasized by the action of indole acetic acid and other auxine-like compounds on their growth. Indeed amoebic growth was enhanced in the presence of these higher plant growth hormones. The differences in the sterol composition of the protozoa we have hitherto examined is related to their sensitivity toward polyene macrolide antibiotics.(ABSTRACT TRUNCATED AT 400 WORDS)
70 citations
TL;DR: In this paper, the authors showed that at concentrations higher than 3 microM, triparanol, buthiobate and low concentrations (less than 0.5 microM) of U18666A, inhibitors of desmosterol delta 24-reductase, of lanosterol 14 alpha-demethylase and of squalene-2,3-epoxide cyclase (EC 5.4.7) respectively, resulted in a decrease of the HMG-CoA reductase activity.
Abstract: Incubating Hep G2 cells for 18 h with triparanol, buthiobate and low concentrations (less than 0.5 microM) of U18666A, inhibitors of desmosterol delta 24-reductase, of lanosterol 14 alpha-demethylase and of squalene-2,3-epoxide cyclase (EC 5.4.99.7) respectively, resulted in a decrease of the HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase activity. However, U18666A at concentrations higher than 3 microM increased the HMG-CoA reductase activity in a concentration-dependent manner. None of these inhibitors influenced directly the reductase activity in Hep G2 cell homogenates. Analysis by t.l.c. of 14C-labelled non-saponifiable lipids formed from either [14C]acetate or [14C]mevalonate during the cell incubations confirmed the sites of action of the drugs used. Beside the 14C-labelled substrates of the blocked enzymes and 14C-labelled cholesterol, another non-saponifiable lipid fraction was observed, which behaves as polar sterols on t.l.c. This was the case with triparanol and at those concentrations of U18666A that decreased the reductase activity, suggesting that polar sterols may play a role in suppressing the reductase activity. In the presence of 30 microM-U18666A (sterol formation blocked) the increase produced by simultaneously added compactin could be prevented by addition of mevalonate. This indicates the existence of a non-sterol mevalonate-derived effector in addition to a sterol-dependent regulation. LDL (low-density lipoprotein), which was shown to be able to decrease the compactin-induced increase in reductase activity, could not prevent the U18666A-induced increase. On the contrary, LDL enhanced the U18666A effect, showing that the LDL regulation is not merely the result of introducing cholesterol to the cells.
50 citations
TL;DR: The results demonstrate that metabolism of the oxygenated biosynthetic intermediate is not required to suppress reductase activity and strongly support the hypothesis that oxygenated 14 alpha-methyl demethylase intermediates are endogenously generated modulators of HMG-CoA reduct enzyme activity.
40 citations
TL;DR: Results establish that lanosterol 14 alpha-methyl demethylation, but not 24,25-epoxylanosterol formation, is required to suppress HMG-CoA reductase in the manner described by Lanosterol demethylase inhibitors.
39 citations
TL;DR: Identity of this gene was confirmed by observing a heme binding region common to all P450s after sequencing the 3' portion of the gene, and based upon tests of its expression in strains of Saccharomyces cerevisiae.
33 citations
TL;DR: A previously described Candida albicans nystatin resistant mutant blocked in 14α-demethylation of lanosterol was shown to also lack all traces of cytochrome P450 as determined by carbon monoxide difference spectra as discussed by the authors.
33 citations
TL;DR: P-450SG1 is the first example of a cytochrome P-450 having a histidine axial ligand trans to thiolate and of a genetically altered cytochamino acid isolated in a homogeneous state.
TL;DR: This work describes a simple assay for measuring squalene epoxidase specific activity in Saccharomyces cerevisiae cell-free extracts, by using [14C] farnesyl pyrophosphate as substrate, and shows thatSqualene 2,3-epoxide-lanosterol cyclase is also a microsome-bound enzyme.
TL;DR: Support is provided for the hypothesis that newly synthesized cholesterol and lanosterol are not in the same membrane and that synthesis of the sterols is not associated with the smooth endoplasmic reticulum.
TL;DR: A simplified synthesis of lanost-8-ene-3β, 32-diol, lanost, 7-ene, 3β-hydroxylanost-7-en-32-al, and 3 β-acetoxylanostan-7α-ol is described.
Abstract: A simplified synthesis of lanost-8-ene-3β, 32-diol, lanost-7-ene-3β, 32-diol, 3β-hydroxylanost-8-en-32-al, and 3β-hydroxylanost-7-en-32-al, in which 3β-acetoxylanostan-7α-ol prepared by the hydrogenation of 3β-acetoxylanost-8-en-7-one is the key compound, is described.
TL;DR: All the thermophilic moulds exhibited avidity for binding sterols to the mycelium, but the ability to bind sterol seemed to depend upon the nature of the organism and the sterol.
Abstract: None of the fourteen thermophilic moulds was able to break down the aliphatic side chain of sterols,viz. cholesterol, lanosterol, sitosterol, and stigmasterol so as to yield 4-androstene-3, 17-dione, 1,4-androstadiene-3, 17-dione and progesterone. InAcremonium alabamensis and.Talaromyces emersonii, cholestenone was detected as a product of fermentation of cholesterol whereas the former yielded stigmastadienone from stigmasterol and sitosterol. Lanosterol appeared to be resistant to fungal bioconversion. All the thermophilic moulds exhibited avidity for binding sterols to the mycelium, but the ability to bind sterol seemed to depend upon the nature of the organism and the sterol.
TL;DR: Observations rule out the hypotheses that either an endogenously synthesized oxygenated cholesterol biosynthetic intermediate or epoxysterol is required to mediate the inhibition of this enzyme by low density lipoprotein.
TL;DR: A 24-epimeric mixture of 4α, 14α, 24-trimethyl-9(11)-cholesten-3-one was synthesized from lanosterol through 4α-14-α,24-trIMethyl-8-choline-3β-ol as discussed by the authors.
Abstract: A 24-epimeric mixture of 4α,14α,24-trimethyl-9(11)-cholesten-3-one was synthesized from lanosterol through 4α,14α,24-trimethyl-8-cholesten-3β-ol and 4α,14α,24-trimethyl-7,11-dioxocholestan-3β-yl acetate as key intermediates.
TL;DR: Measurement of isotope ratios in 5α-stigmast-9(11)-en_ 3β -ol (I), a C 29 -sterol, biosynthesised in Costus speciosus from 3RS-mevalonate -[2- 14 C,4R- 3 H] have shown that squalene is possibly metabolised into I via Δ 9(11) lanosterol (VII) rather than Δ 8(9) lanost
TL;DR: It is indicated that proper membrane cholesterol content is necessary for the maintenance of normal low-density lipoprotein receptor function in NS-1 cells.
TL;DR: 22R-Hydroxylanosterol is prepared from lanosterol with an overall yield of over 30% through the stereospecific coupling of the aldehyde 7 with an arsenic ylide.
Abstract: 22R-Hydroxylanosterol (10) is prepared from lanosterol (1) with an overall yield of over 30%. The key step of the synthesis is the stereospecific coupling of the aldehyde 7 with an arsenic ylide. The same reaction is used to build the side chain of 22R-hydroxydesmosterol (14).
Journal Article•
TL;DR: Results in this paper demonstrate for the first time the accumulation of a fraction of nonsaponifiable lipids identified as lanosterol derivatives and cholesterol precursors formed from [5-14C]mevalonate in experiments carried out in vivo.
Abstract: The in vivo mevalonate incorporation into total nonsaponifiable lipids by chick liver was minimal after hatching and drastically increased between 1-5 days. The hepatic synthesis of different cholesterol precursors emerged sequentially after hatching. Between 1-5 days increased strongly the conversion of mevalonate into squalene and also the formation of oxygenated lanosterol derivatives from squalene. The conversion of squalene became completely active at day 8. Cholesterol formation from lanosterol derivatives was completely activated between 8-11 days. Results in this paper demonstrate for the first time the accumulation of a fraction of nonsaponifiable lipids identified as lanosterol derivatives and cholesterol precursors formed from [5-14C]mevalonate in experiments carried out in vivo. Postnatal evolution of these oxysterols may explain the great increase of 3-hydroxy-3-methylglutaryl-CoA reductase activity found in chick liver between 5-11 days, simultaneous or posterior to the diminution of the oxygenated cholesterol precursors.
01 Nov 1987
TL;DR: The structures of triterpenols from Euphorbia lathyris latex are reported in this article, where a method for quantifying very small amounts of these compounds was developed.
Abstract: The structures of triterpenols, not previously been known, from Euphorbia lathyris latex are reported A method for quantifying very small amounts of these compounds was developed Concerning the biochemistry of the latex, no exogenous cofactors were required for the biosynthesis and the addition of compounds such as NADPAH and ATP do not stimulate the biosynthesis The addition of DTE or a similar anti-oxidant was found to help reduce the oxidation of the latex, thus increasing the length of time that the latex remains active The requirement of a divalent cation and the preference for Mn in the pellet was observed The effect of several inhibitors on the biosynthesis of the triterpenoids was examined Mevinolin was found to inhibit the biosynthesis of the triterpenoids from acetate, but not mevalonate A dixon plot of the inhibition of acetate incorporation showed an I/sub 50/ concentration of 32 muM Fenpropimorph was found to have little or no effect on the biosynthesis Tridemorph was found to inhibit the biosynthesis of all of the triterpenoids with an I/sub 50/ of 4 muM It was also observed that the cyclopropyl containing triterpenols, cycloartenol and 24-methylenecycloartenol were inhibited much more strongly than those containing an 8-9 double bond, lanosterol and 24-methylenelanosterol The evidence indicates, but does not definetely prove, that lanosterol and 24-methylenelanosterol are not made from cycloartenol and 24-methylenecycloartenol via a ring-opening enzyme such as cycloeucalenol-obtusifoliol isomerase The possibilty that cycloartenol is made via lanosterol was investigated by synthesizing 4-R-4-/sup 3/H-mevalonic acid and incubating latex with a mixture of this and /sup 14/C-mevalonic acid From the /sup 3/H//sup 14/C ratio it was shown that cycloartenol and 24-methylenecycloartenol are not made via an intermediate containing as 8-9 double bond 88 refs, 15 figs, 30 tabs
TL;DR: In this article, a simplified synthesis of lanost-8-ene-3β, 32-diol and 3β-hydroxylanost-7-en-32-al is described.
Abstract: A simplified synthesis of lanost-8-ene-3β, 32-diol, lanost-7-ene-3β, 32-diol, 3β-hydroxylanost-8-en-32-al, and 3β-hydroxylanost-7-en-32-al, in which 3β-acetoxylanostan-7α-ol prepared by the hydrogenation of 3β-acetoxylanost-8-en-7-one is the key compound, is described.