Showing papers on "Lanosterol published in 2005"
TL;DR: It is shown that lanosterol, the first sterol intermediate in cholesterol synthesis, potently stimulates ubiquitination of reductase, whereas cholesterol has no effect at 10-fold higher concentrations, and a pair of methyl groups located in the C4 position of Lanosterol confers this differential response.
260 citations
TL;DR: This work studies the influence of cholesterol and its precursors desmosterol and lanosterol on lateral diffusion of phospholipids and sterols by1H pulsed field gradients (PFG) magic angle spinning (MAS) NMR spectroscopy and assumes that the higher activation energies are a reflection of lipid diffusion across domain boundaries.
143 citations
TL;DR: This is the first time such results have been presented for membranes containing the structurally related sterols, ergosterol and lanosterol, and large differences in the influence of these sterols on the membrane thermal area expansion coefficient are observed.
103 citations
TL;DR: It is demonstrated that the lanosterol 14α-demethylase, which converts 24,25-dihydrolanosterol to cholesterol, can be inhibited by the 26-oxygenosterols from G. lucidum, which could lead to novel therapeutic agents that lower blood cholesterol.
Abstract: Ganoderma lucidum is a medicinal fungus belonging to the Polyporaceae family which has long been known in Japan as Reishi and has been used extensively in traditional Chinese medicine. We report the isolation and identification of the 26-oxygenosterols ganoderol A, ganoderol B, ganoderal A, and ganoderic acid Y and their biological effects on cholesterol synthesis in a human hepatic cell line in vitro. We also investigated the site of inhibition in the cholesterol synthesis pathway. We found that these oxygenated sterols from G. lucidum inhibited cholesterol biosynthesis via conversion of acetate or mevalonate as a precursor of cholesterol. By incorporation of 24,25-dihydro-[24,25-3H2]lanosterol and [3-3H]lathosterol in the presence of ganoderol A, we determined that the point of inhibition of cholesterol synthesis is between lanosterol and lathosterol. These results demonstrate that the lanosterol 14α-demethylase, which converts 24,25-dihydrolanosterol to cholesterol, can be inhibited by the 26-oxygenosterols from G. lucidum. These 26-oxygenosterols could lead to novel therapeutic agents that lower blood cholesterol.
100 citations
TL;DR: The recent crystallization of OSC identifies the mechanism of action for this complex enzyme, setting the stage for the design of O SC inhibitors with improved pharmacological properties for cholesterol lowering and treatment of atherosclerosis.
73 citations
TL;DR: The presence of a squalene epoxide/lanosterol cyclase activity, which was suspected in view of the unique 3 beta-hydroxy 4 alpha-methyl steroids of M. capsulatus, was demonstrated by the labelling of lanosterol, and it was shown that this does not derive from Lanosterol by isomerization via a 3-oxo compound.
Abstract: 1. A cell-free system from the bacterium Methylococcus capsulatus was incubated with [12-3H]-squalene; diploptene and diplopterol, normally present in the bacterium, were labelled. 2 The same cell-free system was incubated with (RS)-2,3-epoxy-2,3-dihydro-[3-3H]squalene. Several radioactive 3-hydroxytriterpenes were purifed. Lanosterol, which is normally present in this bacterium, was found labelled as well as 3-epilanosterol. In addition, radioactive 3 alpha-hydroxy and 3 beta-hydroxydiploptene were formed. 3. These data may be explained by the coexistence of two cyclases in M. capsulatus: a squalene/hopane cyclase and a squalene epoxide/lanosterol cyclase. The squalene cyclase exhibits the same lack of substrate specificity as those of Acetobacter pasteurianum and Tetrahymena pyriformis, i.e. in addition to its normal substrate squalene, it can cyclize the two enantiomers of squalene epoxide into 3-hydroxyhopanoids. 4. The presence of a squalene epoxide/lanosterol cyclase activity, which was suspected in view of the unique 3 beta-hydroxy 4 alpha-methyl steroids of M. capsulatus, was demonstrated by the labelling of lanosterol. More surprisingly 3-epilanosterol was also present and labelled. We showed that this does not derive from lanosterol by isomerization via a 3-oxo compound. Therefore the squalene expoxide cyclase of M. capsulatus, like the one of eukaryotes cyclizes the (3S) enantiomer of squalene epoxide into lanosterol. But it is definitely less substrate-specific as it can also cyclize the (3R) enantiomer into 3-epilanosterol.
73 citations
TL;DR: Efforts to modify the catalytic specificity of enzymes consistently show that it is easier to broaden the substrate or product specificity of an accurate enzyme than to restrict the selectivity of one that is promiscuous.
Abstract: Efforts to modify the catalytic specificity of enzymes consistently show that it is easier to broaden the substrate or product specificity of an accurate enzyme than to restrict the selectivity of one that is promiscuous. Described herein are experiments in which cycloartenol synthase was redesigned to become a highly accurate lanosterol synthase. Several single mutants have been described that modify the catalytic specificity of cycloartenol to form some lanosterol. Modeling studies were undertaken to identify combinations of mutations that cooperate to decrease the formation of products other than lanosterol. A double mutant was constructed and characterized and was shown to cyclize oxidosqualene accurately to lanosterol (99%). This catalytic change entailed both relocating polarity with a His477Asn mutation and modifying steric constraints with an Ile481Val mutation.
59 citations
TL;DR: This unique behavior of cholesterol is interpreted as a result of its previously established out-of-plane motion which allows the molecule to cross the bilayer midplane, thereby effectively coupling the bilayers leaflets to form a highly flexible but more stable composite membrane.
46 citations
TL;DR: It is suggested that CYP17, in addition to its 17alpha-hydroxylase/17,20-lyase activity, critical in androgen formation, also expresses a secondary activity, squalene monooxygenase (epoxidase), of a well-established enzyme involved in cholesterol biosynthesis, which may become critical under certain conditions.
Abstract: Cytochrome P450 17alpha-hydroxylase/17,20-lyase (CYP17) is a microsomal enzyme catalyzing two distinct activities, 17alpha-hydroxylase and 17,20-lyase, essential for the biosynthesis of adrenal and gonadal steroids. CYP17 is a potent oxidant, it is present in liver and nonsteroidogenic tissues, and it has been suggested to have catalytic properties distinct to its function in steroid metabolism. To identify CYP17 functions distinct of its 17alpha-hydroxylase/17,20-lyase activity, we used MA-10 mouse tumor Leydig cells known to be defective in 17alpha-hydroxylase/17,20-lyase activity. A CYP17 knocked down MA-10 clone (MA-10(CYP17KD)) was generated by homologous recombination and its steroidogenic capacity was compared with wild-type cells (MA-10(wt)). Although no differences in cell morphology and proliferation rates were observed between these cells, the human chorionic gonadotropin-induced progesterone formation and de novo synthesis of steroids were dramatically reduced in MA-10(CYP17KD) cells; their steroidogenic ability could be rescued in part by transfecting CYP17 DNA into the cells. Knocking down CYP17 mRNA by RNA interference yielded similar results. However, no significant difference was observed in the steroidogenic ability of cells treated with 22R-hydroxycholesterol, which suggested a defect in cholesterol biosynthesis. Incubation of MA-10(CYP17KD) cells with (14)C-labeled squalene resulted in the formation of reduced amounts of radiolabeled cholesterol compared with MA-10(wt) cells. In addition, treatment of MA-10(CYP17KD) cells with various cholesterol substrates indicated that unlike squalene, addition of squalene epoxide, lanosterol, zymosterol, and desmosterol could rescue the hormone-induced progesterone formation. Further in vitro studies demonstrated that expression of mouse CYP17 in bacteria resulted in the expression of squalene monooxygenase activity. In conclusion, these studies suggest that CYP17, in addition to its 17alpha-hydroxylase/17,20-lyase activity, critical in androgen formation, also expresses a secondary activity, squalene monooxygenase (epoxidase), of a well-established enzyme involved in cholesterol biosynthesis, which may become critical under certain conditions.
41 citations
TL;DR: Functional characterization of CYP51G1-Sc expressed in yeast showed that it could demethylate obtusifoliol, as well as nontypical plant sterol biosynthetic intermediates (lanosterol), in contrast with the strong substrate specificity of the previously characterized obtUSifolioiol 14α-demethylases found in other plant species.
Abstract: The sterol 14α-demethylase (CYP51) is the most widely distributed cytochrome P450 gene family being found in all biological kingdoms. It catalyzes the first step following cyclization in sterol biosynthesis, leading to the formation of precursors of steroid hormones, including brassinosteroids, in plants. Most enzymes involved in the plant sterol biosynthesis pathway have been characterized biochemically and the corresponding genes cloned. Genes coding for enzymes promoting substrate modifications before 24-methylenelophenol lead to embryonic and seed defects when mutated, while mutants downstream the 24-methylenelophenol intermediate show phenotypes characteristic of brassinosteroid mutants. By a differential display approach, we have isolated a fertilization-induced gene, encoding a sterol 14α-demethylase enzyme, named CYP51G1-Sc. Functional characterization of CYP51G1-Sc expressed in yeast (Saccharomyces cerevisiae) showed that it could demethylate obtusifoliol, as well as nontypical plant sterol biosynthetic intermediates (lanosterol), in contrast with the strong substrate specificity of the previously characterized obtusifoliol 14α-demethylases found in other plant species. CYP51G1-Sc transcripts are mostly expressed in meristems and in female reproductive tissues, where they are induced following pollination. Treatment of the plant itself with obtusifoliol induced the expression of the CYP51G1-Sc mRNA, suggesting a possible role of this transient biosynthetic intermediate as a bioactive signaling lipid molecule. Furthermore, treatments of leaves with 14C-labeled obtusifoliol demonstrated that this sterol could be transported in distal parts of the plant away from the sprayed leaves. Arabidopsis (Arabidopsis thaliana) CYP51 homozygous knockout mutants were also lethal, suggesting important roles for this enzymatic step and its substrate in plant development.
40 citations
TL;DR: It is demonstrated that the fucosterol had a 3H atom located at C-25 and therefore proves that hydrogen (tritium) migration from C-24 to C- 25 occurs during alkylation of the phytosterol side chain.
Abstract: Fucosterol biosynthesised by Fucus spiralis from [2-14C,(4R)-4-3H1] mevalonic acid has a 3H/14C atomic ratio of 3/5. Isomerisation of the labelled fucosteryl acetate gave 3β-acetoxystigmasta-5,24-diene with a 3H/14C atomic ratio of 2/5. This demonstrated that the fucosterol had a 3H atom located at C-25 and therefore proves that hydrogen (tritium) migration from C-24 to C-25 occurs during alkylation of the phytosterol side chain. Cycloartenol and 24-methylene cycloartanol also isolated from the Fucus spiralis were shown to be radioactively labelled, there was no evidence of radioactive lanosterol. Tritium was shown to be present at C-3 of the biosynthesised cycloartenol but was absent from C-3 of the fucosterol.
TL;DR: Several critical residues from oxidationosqualene-lanosterol cyclase (ERG7) from Saccharomyces cerevisiae and oxidosqualenecycloartenol synthase (CAS) from Arabidopsis thaliana are identified and demonstrated their roles in facilitating tetracyclic formation and/or stabilizing the lanosteryl cation for deprotonation.
Abstract: Oxidosqualene cyclases catalyze the biotransformation of acyclic (3S)-2,3-oxidosqualene (OS) to a variety of polycyclic sterols and triterpenoids, generating over 100 distinct triterpenoid skeletons with the formula C30H50O. [1–3,4 and references therein] Product specificity is species-dependent and precisely controlled by the prefolded substrate conformation as well as by interactions between the carbocationic intermediate for deprotonation and the functional groups of catalytic amino acid residues of the enzyme. The transformation mechanisms of this single class of enzymes can vary widely. For example, the triterpenes lanosterol, cycloartenol, and parkeol are formed from a preorganized chair–boat–chair substrate conformation of OS, and cationic cyclization to the protosteryl cation is followed by skeletal rearrangements until the final deprotonation step. Formation of the pentacyclic b-amyrin and lupeol proceed similarly except that OS is in the chair–chair–chair conformation (this results in stereochemical differences in the products relative to the chair–boat–chair substrate conformation), and the cationic cyclization to the dammarenyl cation is followed by annulation of a fifth ring. Various strategies have been used to probe the complex cyclization/rearrangement reaction mechanism, both for the purpose of understanding these complex enzymes and also to engineer cyclases to generate new product profiles. For example, site-directed mutagenesis was used to identify the residues responsible for the product specificity of b-amyrin synthase (PNY) and lupeol synthase (OEW). Two residues of PNY from Panax ginseng, Trp259 and Tyr261, were found to play important roles in the reaction mechanism to direct b-amyrin and/or lupeol formation. We and others independently identified several critical residues from oxidosqualene-lanosterol cyclase (ERG7) from Saccharomyces cerevisiae and oxidosqualenecycloartenol synthase (CAS) from Arabidopsis thaliana, and demonstrated their roles in facilitating tetracyclic formation and/or stabilizing the lanosteryl cation for deprotonation, as
TL;DR: Interestingly, when CREB is not limiting, the increasing amounts of SREBP-1a fail to transactivate the CYP51 promoter above the CREB-only level, suggesting that hormones might have an important role in regulating cholesterogenesis in vivo.
Abstract: Lanosterol 14α-demethylase (CYP51) responds to cholesterol feedback regulation through sterol regulatory element binding proteins (SREBPs). The proximal promoter of CYP51 contains a conserved region with clustered regulatory elements: GC box, cAMP-response elements (CRE-like), and sterol regulatory element (SRE). In lipid-rich (SREBP-poor) conditions, the CYP51 mRNA drops gradually, the promoter activity is diminished, and no DNA-protein complex is observed at the CYP51-SRE1 site. The majority of cAMP-dependent transactivation is mediated through a single CRE (CYP51-CRE2). Exposure of JEG-3 cells to forskolin, a mediator of the cAMP-dependent signaling pathway, provokes an immediate early response of CYP51, which has not been described before for any cholesterogenic gene. The CYP51 mRNA increases up to 4-fold in 2 h and drops to basal level after 4 h. The inducible cAMP early repressor (ICER) is involved in attenuation of transcription. Overexpressed CRE-binding protein (CREB)/CRE modulator (CREM) transac...
TL;DR: The present results demonstrate that selected cholesterol analogs may act as cytostatic agents, interrupting cell cycle progression specifically in the G2/M phase.
TL;DR: Results indicate that exit of lanosterol from LP occurs independently of functional Erg11p, random supply of sterol intermediates to all organelles of erg11Delta erg3Delta appears to compensate for the lack of ergosterol in this mutant, and preferential sorting of ergostol in wild type, but also of ergosta-7,22-dienol in erg3 Delta, supplies sterol to the plasma membrane.
TL;DR: It is established, through kinetic and spectral analysis, that MT FdR preferentially uses NADH as cofactor, and forms a complex with mycobacterial ferredoxin (MT Fdx) and MT CYP51, a cytochrome P450 (CYP) from M. tuberculosis that is similar to lanosterol 14alpha-demethylase isozymes.
TL;DR: The content of ergosterol in both the sensitive and resistant C. albicans showed depletion, whereas the squalene showed accumulation especially in the sensitive isolates determined with the method developed.
TL;DR: Observations indicate that CP-320626 inhibits cholesterolgenesis via direct inhibition of CYP51, and that this is the mechanism whereby CP- 320626 lowers plasma cholesterol in experimental animals.
Patent•
25 Feb 2005
TL;DR: In this paper, the authors proposed a method for modulating the rate of cholesterol synthesis in a mammal by using C27 modified sterols, particularly derivatives of intermediates in cholesterol synthesis.
Abstract: This invention relates to oxysteroids and oxysteroid hormones which have been identified. These oxysteroids are C27 modified sterols, particularly derivatives of intermediates in cholesterol synthesis, including lanosterol, zymosterol and desmosterol, including C27 diol and C27 acid derivatives, as well as related compounds and analogs thereof. The oxysteroids are capable of binding to or otherwise interacting with orphan nuclear receptors to result in modulation of gene expression. The invention further relates to methods of modulating the rate of cholesterol synthesis in a mammal. More specifically, the invention relates to treatment of cholesterol-related conditions which are improved or ameliorated by modulating the rate of cholesterol synthesis or cholesterol metabolism in a human in need thereof by administration of these oxysteroids, analogs or antagonists thereof. Assays for identification of analogs, antagonists or modulators of these oxysteroids are also provided.
TL;DR: S23515, and potentially other imidazoline-like drugs, could exert hypolipidemic effects in addition to their hypotensive activities, and this work suggests that these molecules were proposed to play an additional role in cardiovascular diseases by acting on glucose and lipid metabolism.
TL;DR: The results suggest that the fungicidal activity of these inhibitors is related to their inhibitory effect on LS, and its use for screening molecules to find fungal inhibitors is described.
Journal Article•
TL;DR: TTS-12 can inhibit the growth of Candida albicans and ultimately lead to cell death and it might inhibit the bio-synthesis of ergosterol in CandidaAlbicans.
Abstract: Objective: To study the effect of TTS-12 on the sterol bio-synthetical pathway in Candida albicans. Methods: The concentrations of ergosterol and lanosterol in Candida albicans before and after cultured with TTS-12 were determined quantitatively with GC-MS. Results: The concentrations of ergosterol and lanosterol in Candida albicans control group were (53.2± 4.8)% and (3.5±0.6 )%, respectively. The concentrations of ergosterol and lanosterol in Candida albicans treated with TTS-12 were (5.6±0.8)% and (16.5±3.2)%, respectively. Conclusion: TTS-12 can inhibit the growth of Candida albicans and ultimately lead to cell death. It might inhibit the bio-synthesis of ergosterol in Candida albicans.
TL;DR: In this paper, the electronic and energetic parameters of lanosterol and other structurally related steroids, including epilanosterol, were analyzed to find differences of selectivity in each molecule, along with total energy and hardness.
Abstract: 14α-demethylation is the reaction which leads directly to norlanosterol from lanosterol, and is carried out exclusively by lanosterol structure. To discover the features, which make lanosterol a unique molecule able to undergo this demethylation, the electronic and energetic parameters of lanosterol and other structurally related steroids, were calculated. Local and global parameters were analyzed, in order to insight into the reactivity and selectivity of every molecule studied. Electrostatic potential maps were used to find differences of selectivity in each molecule, along with total energy and hardness, discovering the differences in reactivity. Lanosterol shows specific orientation and unique shape of electrostatic potential map, which does not appear in other structures, except epilanosterol, because it differs only in the orientation of a hydroxyl group, therefore they present many similarities but many differences also. For this reason, epilanosterol has a similar shape of electrostatic potential map, but not its orientation. Aoyama et al. have found, three essential structural features in lanosterol to be demethylated, which generate a specific electrostatic potential map, the hydroxyl group on C-3, the position of the double bound between C8 and C9 on cycle B, and the side chain double bond. Our study agrees with some biochemical studies, which reveal that there are three key features essential for substrate recognition by the enzyme P-450 14DM . We think the present study is an alternative methodology to find features which are related with some parameters obtained via theoretical calculations.