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Lanosterol synthase

About: Lanosterol synthase is a research topic. Over the lifetime, 164 publications have been published within this topic receiving 5954 citations. The topic is also known as: lanosterol synthase (2,3-oxidosqualene-lanosterol cyclase) & lanosterol synthase.


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Journal ArticleDOI
TL;DR: The identification of LSS as causal gene for autosomal-recessive HS highlights the importance of the cholesterol pathway in hair follicle biology and may facilitate novel therapeutic approaches for hair loss disorders in general.
Abstract: Hypotrichosis simplex (HS) is a rare form of hereditary alopecia characterized by childhood onset of diffuse and progressive scalp and body hair loss. Although research has identified a number of causal genes, genetic etiology in about 50% of HS cases remains unknown. The present report describes the identification via whole-exome sequencing of five different mutations in the gene LSS in three unrelated families with unexplained, potentially autosomal-recessive HS. Affected individuals showed sparse to absent lanugo-like scalp hair, sparse and brittle eyebrows, and sparse eyelashes and body hair. LSS encodes lanosterol synthase (LSS), which is a key enzyme in the cholesterol biosynthetic pathway. This pathway plays an important role in hair follicle biology. After localizing LSS protein expression in the hair shaft and bulb of the hair follicle, the impact of the mutations on keratinocytes was analyzed using immunoblotting and immunofluorescence. Interestingly, wild-type LSS was localized in the endoplasmic reticulum (ER), whereas mutant LSS proteins were localized in part outside of the ER. A plausible hypothesis is that this mislocalization has potential deleterious implications for hair follicle cells. Immunoblotting revealed no differences in the overall level of wild-type and mutant protein. Analyses of blood cholesterol levels revealed no decrease in cholesterol or cholesterol intermediates, thus supporting the previously proposed hypothesis of an alternative cholesterol pathway. The identification of LSS as causal gene for autosomal-recessive HS highlights the importance of the cholesterol pathway in hair follicle biology and may facilitate novel therapeutic approaches for hair loss disorders in general.

48 citations

Journal ArticleDOI
TL;DR: The β‐amyrin synthase purified in this study showed a significantly higher catalytic efficiency than those of the two reported lanosterol synthases, and this is the first report of the kinetic data of the mutated enzymes targeted for the DCTAE(485–489) motif, which is a putative initiation site for the polycyclization reaction.
Abstract: β-Amyrin, a natural triterpene, is widely distributed in the plant kingdom, and its pentacyclic skeleton is produced by oxidosqualene cyclase (OSC). OSC enzymes are classified as membrane proteins, and they catalyze the polycyclization reaction of (3S)-2,3-oxidosqualene to yield nearly 150 different cyclic triterpene skeletons. To date, no report has described the successful purification and characterization of plant β-amyrin synthase. The β-amyrin synthase from Euphorbia tirucalli (EtAS) was expressed as a polyhistidine-tagged protein in Saccharomyces cerevisiae GIL77, which lacks the lanosterol synthase gene. The expression yield, determined by western blotting analysis, was 5-7 mg. By Ni(2+) -nitrilotriacetic acid affinity column chromatography and careful selection of the proper imidazole concentration during the purification processes of washing and elution, a single band was successfully obtained on SDS/PAGE. We then tested the effects of four detergents on the enzyme activity. Supplementation with Triton X-100 at a concentration of 0.05% yielded the highest activity. The optimal pH and temperature were 7.0 and 30 °C, respectively. The kinetic parameters, K(m) and k(cat) , were determined to be 33.8 ± 0.53 μm and 46.4 ± 0.68 min(-1), respectively. To the best of our knowledge, there are no reports describing both K(m) and k(cat) for OSCs except for two examples of rat and bovine lanosterol synthases. The β-amyrin synthase purified in this study showed a significantly higher catalytic efficiency (k(cat)/K(m)) (~ 10(3)-fold) than those of the two reported lanosterol synthases. Gel-filtration HPLC indicated that the OSC exists as a monomer, and the eluted OSC retained its activity. Furthermore, the inhibition constants K(i) and IC(50) and types of inhibition by iminosqualene, Ro48-8071 and U18666A were determined, and indicated that iminosqualene and Ro48-8071 are potent inhibitors. Additionally, this is the first report of the kinetic data of the mutated enzymes targeted for the DCTAE(485-489) motif, which is a putative initiation site for the polycyclization reaction. No activity of the D485N variant and significantly decreased activity of the C564A variant were found, definitively demonstrating that the acidic carboxyl residue Asp485 serves as a proton donor to initiate the polycyclization reaction, and that Cys564 is involved in hydrogen bond formation with the carboxyl residue Asp458 to enhance the acidity. The CD spectrum is the first to be reported for OSCs, and the CD spectra of the wild-type and the mutated EtASs were almost the same, indicating that the protein architecture was not altered by these mutations.

47 citations

Journal ArticleDOI
TL;DR: It is demonstrated that lack of the hydrophobic domains prevents at least in part the association of the proteins with lipid particles and causes their retention to the ER, which strongly supports the view that ER and lipid particles are related organelles.

46 citations

Journal ArticleDOI
TL;DR: Results gained from homology modeling of human OSC based on structural information of SHC from Alicyclobacillus acidocaldarius are discussed and aStructural insight should strongly stimulate structure‐based design of antifungal or cholesterol‐lowering drugs.
Abstract: 2,3-Oxidosqualene cyclases (OSC) are key enzymes in sterol biosynthesis. They catalyze the stereoselective cyclization and skeletal rearrangement of (3S)-2,3-oxidosqualene to lanosterol in mammals and fungi and to cycloartenol in algae and higher plants. Sequence information and proposed mechanism of 2,3-oxidosqualene cyclases are closely related to those of squalene-hopene cyclases (SHC), which represent functional analogs of OSCs in bacteria. SHCs catalyze the cationic cyclization cascade converting the linear triterpene squalene to fused ring compounds called hopanoids. High stereoselectivity and precision of the skeletal rearrangements has aroused the interest of researchers for nearly half a century, and valuable data on studying mechanistic details in the complex enzyme-catalyzed cyclization cascade has been collected. Today, interest in cyclases is still unbroken, because OSCs became targets for the development of antifungal and hypocholesterolemic drugs. However, due to the large size and membrane-bound nature of OSCs, three-dimensional structural information is still not available, thus preventing a complete understanding of the atomic details of the catalytic mechanism. In this work, we discuss results gained from homology modeling of human OSC based on structural information of SHC from Alicyclobacillus acidocaldarius and propose a structural model of human OSC. The model is in accordance with previously performed experimental studies with mechanism-based suicide inhibitors and mutagenesis experiments with altered activity and product specificity. Structural insight should strongly stimulate structure-based design of antifungal or cholesterol-lowering drugs.

45 citations

Journal ArticleDOI
TL;DR: To identify mutants that deprotonate differently, randomly generated mutant cycloartenol synthases were selected in a yeast lanosterol synthase mutant and two novel mutants were uncovered.

44 citations

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20216
20206
20194
20188
201711
20165