Lanosterol

About: Lanosterol is a research topic. Over the lifetime, 1239 publications have been published within this topic receiving 36737 citations. The topic is also known as: (3β)-lanosta-8,24-dien-3-ol & (3β,20R)-lanosta-8,24-dien-3-ol.

Characterization of the Saccharomyces cerevisiae ERG27 gene encoding the 3-keto reductase involved in C-4 sterol demethylation

Abstract: The last unidentified gene encoding an enzyme involved in ergosterol biosynthesis in Saccharomyces cerevisiae has been cloned. This gene, designated ERG27, encodes the 3-keto sterol reductase, which, in concert with the C-4 sterol methyloxidase (ERG25) and the C-3 sterol dehydrogenase (ERG26), catalyzes the sequential removal of the two methyl groups at the sterol C-4 position. We developed a strategy to isolate a mutant deficient in converting 3-keto to 3-hydroxy-sterols. An ergosterol auxotroph unable to synthesize sterol or grow without sterol supplementation was mutagenized. Colonies were then selected that were nystatin-resistant in the presence of 3-ketoergostadiene and cholesterol. A new ergosterol auxotroph unable to grow on 3-ketosterols without the addition of cholesterol was isolated. The gene (YLR100w) was identified by complementation. Segregants containing the YLR100w disruption failed to grow on various types of 3-keto sterol substrates. Surprisingly, when erg27 was grown on cholesterol- or ergosterol-supplemented media, the endogenous compounds that accumulated were noncyclic sterol intermediates (squalene, squalene epoxide, and squalene dioxide), and there was little or no accumulation of lanosterol or 3-ketosterols. Feeding experiments in which erg27 strains were supplemented with lanosterol (an upstream intermediate of the C-4 demethylation process) and cholesterol (an end-product sterol) demonstrated accumulation of four types of 3-keto sterols identified by GC/MS and chromatographic properties: 4-methyl-zymosterone, zymosterone, 4-methyl-fecosterone, and ergosta-7,24 (28)-dien-3-one. In addition, a fifth intermediate was isolated and identified by 1H NMR as a 4-methyl-24,25-epoxy-cholesta-7-en-3-one. Implications of these results are discussed.

Isolation and Characterization of the Gene Encoding 2,3-Oxidosqualene- Lanosterol Cyclase from Saccharomyces cerevisiae

Abstract: The ERG7 gene encoding oxidosqualene-lanosterol cyclase [(S)-2,3-epoxysqualene mutase (cyclizing, lanosterol forming), EC 5.4.99.7] from Saccharomyces cerevisiae has been cloned by genetic complementation of a cyclase-deficient erg7 strain. The DNA sequence of this gene has been determined and found to contain an open reading frame of 2196 nt (including stop codon) that encodes a predicted protein of 731 amino acids. The predicted molecular mass of the S. cerevisiae cyclase, 83.4 kDa, is similar to the predicted molecular masses of the oxidosqualene-lanosterol cyclase from Candida albicans and the oxidosqualene-cycloartenol cyclase from Arabidopsis thaliana, as well as to the molecular masses assigned to vertebrate oxidosqualene-lanosterol cyclases; however, it is substantially larger than the molecular mass assigned to purified S. cerevisiae cyclase. At the level of DNA and predicted amino acid sequences, the S. cerevisiae and C. albicans cyclases share 56% and 63% identity, respectively. Tryptophan and tyrosine residues are unusually abundant in the predicted amino acid sequences of (oxido)-squalene cyclases, leading to a hypothesis that electron-rich aromatic side chains from these residues are essential features of cyclase active sites.

Differential effects of cholesterol and lanosterol on artificial membranes (glucose permeability/ 13 C nuclear magnetic resonance spectroscopy)

Abstract: The effects of cholesterol, 4,4-dimethylcholesterol, and lanosterol (4,4',14α-trimethyl-δ 8,24 -cholestadiene-3β-ol) on some properties of lecithin vesicles have been compared. Unlike cholesterol, lanosterol retards the exit of trapped glucose from phospholipid vesicles only slightly. The 13 C nuclear magnetic resonance spectrum of cholesterol/lecithin vesicles shows no resonances attributable to the sterol. By contrast, several resonances attributable to quaternary carbon atoms or methyl groups are seen in the 13 C nuclear magnetic resonance spectrum of lanosterol/lecithin vesicles, indicating that lanosterol is much less immobilized than cholesterol. Because the membrane behavior of 4,4-dimethylcholesterol is closely similar to that of cholesterol, it is concluded that the axial 14-α-methyl group is responsible for the lessened membrane immobilization of lanosterol. The results emphasize the importance of a planar sterol α-face for interaction with phospholipid acyl chains.

Sterol phylogenesis and algal evolution.

Abstract: The stereochemistry of several sterol precursors and end products synthesized by two fungal-like micro-organisms Prototheca wickerhamii (I) and Dictyostelium discoideum (II) have been determined by chromatographic (TLC, GLC, and HPLC) and spectral (UV, MS, and 1H NMR) methods. From I and II the following sterols were isolated from the cells: cycloartenol, cyclolaudenol, 24(28)-methylenecycloartanol, ergosterol, protothecasterol, 4alpha-methylergostanol, 4alpha-methylclionastanol, clionastanol, 24beta-ethylcholesta-8,22-enol, and dictyosterol. In addition, the mechanism of C-24 methylation was investigated in both organisms by feeding to I [2-3H]lanosterol, [2-3H]cycloartenol, [24-3H]lanosterol, and [methyl-2H3]methionine and by feeding to II [methyl-2H3]methionine. The results demonstrate that the 24beta configuration is formed by different alkylation routes in I and II. The Delta25(27) route operates in I while the Delta24(28) route operates in II. Based on what is known in the literature regarding sterol distribution and phylogenesis together with our findings that the stereochemical outcome of squalene oxide cyclization leads to the production of cycloartenol rather than lanosterol (characteristic of the fungal genealogy) and the chirality of the C-24 alkyl group is similar in the two nonphotosynthetic microbes (beta oriented), we conclude that Prototheca is an apoplastic Chlorella (i.e., an alga) and that Dictyostelium as well as the other soil amoebae that synthesize cycloartenol evolved from algal rather than fungal ancestors.