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Gan Q, Zheng H, Li X, Li J, Ma J, Zhang Y, Han J, Zhang L, Zhou W, Lu Y. Solving the Jigsaw puzzle of phytosterol diversity by a novel sterol methyltransferase from Zea mays. J Steroid Biochem Mol Biol 2024; 240:106498. [PMID: 38447903 DOI: 10.1016/j.jsbmb.2024.106498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 11/05/2023] [Accepted: 03/03/2024] [Indexed: 03/08/2024]
Abstract
Phytosterols are vital structural and regulatory components in plants. Zea mays produces a series of phytosterols that are specific to corn. However, the underline biosynthetic mechanism remains elusive. In this study, we identified a novel sterol methyltransferase from Z. mays (ZmSMT1-2) which showed a unique feature compared with documented plant SMTs. ZmSMT1-2 showed a substrate preference for cycloartenol. Using S-adenosyl-L-methionine (AdoMet) as a donor, ZmSMT1-2 converted cycloartenol into alkylated sterols with unique side-chain architectures, including Δ25(27) (i.e., cyclolaudenol and cycloneolitsol) and Δ24(25) (i.e., cyclobranol) sterols. Cycloneolitsol is identified as a product of SMTs for the first time. Our discovery provides a previously untapped mechanism for phytosterol biosynthesis and adds another layer of diversity of sterol biosynthesis.
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Affiliation(s)
- Qinhua Gan
- School of Tropical Crops, Hainan University, Haikou 570228, China; Engineering & Research Center of Marine Bioactives and Bioproducts of Hainan Province, Haikou 570228, China; Haikou Technology Innovation Center for Research and Utilization of Algal Bioresources, Haikou 570228, China
| | - Haifeng Zheng
- State Key Laboratory of Marine Resource Utilization in the South China Sea, School of Marine Biology and Fisheries, Hainan University, Haikou 570228, China
| | - Xinyu Li
- State Key Laboratory of Marine Resource Utilization in the South China Sea, School of Marine Biology and Fisheries, Hainan University, Haikou 570228, China
| | - Jing Li
- School of Biological Sciences, The University of Western Australia, Perth 6009, Australia
| | - Jingxue Ma
- State Key Laboratory of Marine Resource Utilization in the South China Sea, School of Marine Biology and Fisheries, Hainan University, Haikou 570228, China; Engineering & Research Center of Marine Bioactives and Bioproducts of Hainan Province, Haikou 570228, China; Haikou Technology Innovation Center for Research and Utilization of Algal Bioresources, Haikou 570228, China
| | - Yuji Zhang
- State Key Laboratory of Marine Resource Utilization in the South China Sea, School of Marine Biology and Fisheries, Hainan University, Haikou 570228, China
| | - Jiakun Han
- Jining Academy of Agricultural Sciences, Jining 272031, China
| | - Lin Zhang
- Shandong Rongchen Pharmaceuticals Inc, Qingdao 266061, China
| | - Wenxu Zhou
- State Key Laboratory of Marine Resource Utilization in the South China Sea, School of Marine Biology and Fisheries, Hainan University, Haikou 570228, China; School of Biological Sciences, The University of Western Australia, Perth 6009, Australia.
| | - Yandu Lu
- State Key Laboratory of Marine Resource Utilization in the South China Sea, School of Marine Biology and Fisheries, Hainan University, Haikou 570228, China; Engineering & Research Center of Marine Bioactives and Bioproducts of Hainan Province, Haikou 570228, China; Haikou Technology Innovation Center for Research and Utilization of Algal Bioresources, Haikou 570228, China; Key Laboratory of Tropical Hydrobiotechnology of Hainan Province, Haikou 570228, China.
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2
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Aberle B, Kowalczyk D, Massini S, Egler-Kemmerer AN, Gergel S, Hammer SC, Hauer B. Methylation of Unactivated Alkenes with Engineered Methyltransferases To Generate Non-natural Terpenoids. Angew Chem Int Ed Engl 2023; 62:e202301601. [PMID: 36997338 DOI: 10.1002/anie.202301601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/30/2023] [Accepted: 03/30/2023] [Indexed: 04/01/2023]
Abstract
Terpenoids are built from isoprene building blocks and have numerous biological functions. Selective late-stage modification of their carbon scaffold has the potential to optimize or transform their biological activities. However, the synthesis of terpenoids with a non-natural carbon scaffold is often a challenging endeavor because of the complexity of these molecules. Herein we report the identification and engineering of (S)-adenosyl-l-methionine-dependent sterol methyltransferases for selective C-methylation of linear terpenoids. The engineered enzyme catalyzes selective methylation of unactivated alkenes in mono-, sesqui- and diterpenoids to produce C11 , C16 and C21 derivatives. Preparative conversion and product isolation reveals that this biocatalyst performs C-C bond formation with high chemo- and regioselectivity. The alkene methylation most likely proceeds via a carbocation intermediate and regioselective deprotonation. This method opens new avenues for modifying the carbon scaffold of alkenes in general and terpenoids in particular.
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Affiliation(s)
- Benjamin Aberle
- Department of Technical Biochemistry, Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Daniel Kowalczyk
- Department of Technical Biochemistry, Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Simon Massini
- Department of Technical Biochemistry, Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Alexander-N Egler-Kemmerer
- Department of Technical Biochemistry, Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Sebastian Gergel
- Department of Technical Biochemistry, Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
- Faculty of Chemistry, Organic Chemistry and Biocatalysis, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Stephan C Hammer
- Department of Technical Biochemistry, Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
- Faculty of Chemistry, Organic Chemistry and Biocatalysis, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Bernhard Hauer
- Department of Technical Biochemistry, Institute of Biochemistry and Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
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3
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Brown MO, Olagunju BO, Giner JL, Welander PV. Sterol methyltransferases in uncultured bacteria complicate eukaryotic biomarker interpretations. Nat Commun 2023; 14:1859. [PMID: 37012227 PMCID: PMC10070321 DOI: 10.1038/s41467-023-37552-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 03/22/2023] [Indexed: 04/05/2023] Open
Abstract
Sterane molecular fossils are broadly interpreted as eukaryotic biomarkers, although diverse bacteria also produce sterols. Steranes with side-chain methylations can act as more specific biomarkers if their sterol precursors are limited to particular eukaryotes and are absent in bacteria. One such sterane, 24-isopropylcholestane, has been attributed to demosponges and potentially represents the earliest evidence for animals on Earth, but enzymes that methylate sterols to give the 24-isopropyl side-chain remain undiscovered. Here, we show that sterol methyltransferases from both sponges and yet-uncultured bacteria function in vitro and identify three methyltransferases from symbiotic bacteria each capable of sequential methylations resulting in the 24-isopropyl sterol side-chain. We demonstrate that bacteria have the genomic capacity to synthesize side-chain alkylated sterols, and that bacterial symbionts may contribute to 24-isopropyl sterol biosynthesis in demosponges. Together, our results suggest bacteria should not be dismissed as potential contributing sources of side-chain alkylated sterane biomarkers in the rock record.
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Affiliation(s)
- Malory O Brown
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Babatunde O Olagunju
- Department of Chemistry, State University of New York-Environmental Science and Forestry, Syracuse, NY, 13210, USA
| | - José-Luis Giner
- Department of Chemistry, State University of New York-Environmental Science and Forestry, Syracuse, NY, 13210, USA
| | - Paula V Welander
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA.
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4
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Elias D, Hervay NT, Jacko J, Morvova M, Valachovic M, Gbelska Y. Erg6p is essential for antifungal drug resistance, plasma membrane properties and cell wall integrity in Candida glabrata. FEMS Yeast Res 2022; 21:6680247. [PMID: 36047961 DOI: 10.1093/femsyr/foac045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/18/2022] [Accepted: 08/30/2022] [Indexed: 11/13/2022] Open
Abstract
ERG6 gene encodes C-24 methyltransferase, one of the specific enzymes that differ in mammalian and yeast sterol biosynthesis. To explore the function of CgErg6p in the yeast pathogen Candida glabrata, we have constructed the Cgerg6Δ deletion mutant. We found that C. glabrata cells lacking CgErg6p exhibit reduced susceptibility to both antifungal azoles and polyenes. The reduced content of ergosterol in the Cgerg6 deletion mutant was accompanied by increased expression of genes encoding the last steps of the ergosterol biosynthetic pathway. The absence of CgErg6p leads to plasma membrane hyperpolarization and decrease in its fluidity compared to the parental C. glabrata strain. The absence of sterols containing C-24 alkyls influenced the susceptibility of Cgerg6Δ mutant cells to alkali metal cations and several other metabolic inhibitors. Our results thus show that sterols lacking C-24 alkyls are not sufficient substitutes for maintaining yeast plasma membrane function. The absence of CgErg6p influences also the cell wall integrity and calcineurin signaling in C. glabrata.
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Affiliation(s)
- Daniel Elias
- Faculty of Natural Sciences, Department of Microbiology and Virology, Comenius University in Bratislava, Ilkovicova 6, 842 15 Bratislava, Slovak Republic
| | - Nora Toth Hervay
- Faculty of Natural Sciences, Department of Microbiology and Virology, Comenius University in Bratislava, Ilkovicova 6, 842 15 Bratislava, Slovak Republic
| | - Juraj Jacko
- Faculty of Mathematics, Physics and Informatics, Department of Nuclear Physics and Biophysics, Comenius University in Bratislava, Mlynska dolina, 842 48 Bratislava, Slovak Republic
| | - Marcela Morvova
- Faculty of Mathematics, Physics and Informatics, Department of Nuclear Physics and Biophysics, Comenius University in Bratislava, Mlynska dolina, 842 48 Bratislava, Slovak Republic
| | - Martin Valachovic
- Institute of Animal Biochemistry and Genetics CBS SAS, Dubravska cesta 9, 840 05 BratislavaSlovak Republic
| | - Yvetta Gbelska
- Faculty of Natural Sciences, Department of Microbiology and Virology, Comenius University in Bratislava, Ilkovicova 6, 842 15 Bratislava, Slovak Republic
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5
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Girard J, Lanneau G, Delage L, Leroux C, Belcour A, Got J, Collén J, Boyen C, Siegel A, Dittami SM, Leblanc C, Markov GV. Semi-Quantitative Targeted Gas Chromatography-Mass Spectrometry Profiling Supports a Late Side-Chain Reductase Cycloartenol-to-Cholesterol Biosynthesis Pathway in Brown Algae. FRONTIERS IN PLANT SCIENCE 2021; 12:648426. [PMID: 33986764 PMCID: PMC8112355 DOI: 10.3389/fpls.2021.648426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 04/06/2021] [Indexed: 05/08/2023]
Abstract
Sterols are biologically important molecules that serve as membrane fluidity regulators and precursors of signaling molecules, either endogenous or involved in biotic interactions. There is currently no model of their biosynthesis pathways in brown algae. Here, we benefit from the availability of genome data and gas chromatography-mass spectrometry (GC-MS) sterol profiling using a database of internal standards to build such a model. We expand the set of identified sterols in 11 species of red, brown, and green macroalgae and integrate these new data with genomic data. Our analyses suggest that some metabolic reactions may be conserved despite the loss of canonical eukaryotic enzymes, like the sterol side-chain reductase (SSR). Our findings are consistent with the principle of metabolic pathway drift through enzymatic replacement and show that cholesterol synthesis from cycloartenol may be a widespread but variable pathway among chlorophyllian eukaryotes. Among the factors contributing to this variability, one could be the recruitment of cholesterol biosynthetic intermediates to make signaling molecules, such as the mozukulins. These compounds were found in some brown algae belonging to Ectocarpales, and we here provide a first mozukulin biosynthetic model. Our results demonstrate that integrative approaches can already be used to infer experimentally testable models, which will be useful to further investigate the biological roles of those newly identified algal pathways.
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Affiliation(s)
- Jean Girard
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
| | - Goulven Lanneau
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
- CNRS, Plateforme Corsaire-METABOMER (FR2424), Station Biologique de Roscoff, Sorbonne Université, Roscoff, France
| | - Ludovic Delage
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
| | - Cédric Leroux
- CNRS, Plateforme Corsaire-METABOMER (FR2424), Station Biologique de Roscoff, Sorbonne Université, Roscoff, France
| | - Arnaud Belcour
- Univ Rennes, Inria, CNRS, IRISA, Equipe Dyliss, Rennes, France
| | - Jeanne Got
- Univ Rennes, Inria, CNRS, IRISA, Equipe Dyliss, Rennes, France
| | - Jonas Collén
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
| | - Catherine Boyen
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
| | - Anne Siegel
- Univ Rennes, Inria, CNRS, IRISA, Equipe Dyliss, Rennes, France
| | - Simon M. Dittami
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
| | - Catherine Leblanc
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
| | - Gabriel V. Markov
- CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Sorbonne Université, Roscoff, France
- *Correspondence: Gabriel V. Markov,
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6
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Zhou W, Fisher PM, Vanderloop BH, Shen Y, Shi H, Maldonado AJ, Leaver DJ, Nes WD. A nematode sterol C4α-methyltransferase catalyzes a new methylation reaction responsible for sterol diversity. J Lipid Res 2019; 61:192-204. [PMID: 31548366 PMCID: PMC6997595 DOI: 10.1194/jlr.ra119000317] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 09/22/2019] [Indexed: 11/28/2022] Open
Abstract
Primitive sterol evolution plays an important role in fossil record interpretation and offers potential therapeutic avenues for human disease resulting from nematode infections. Recognizing that C4-methyl stenol products [8(14)-lophenol] can be synthesized in bacteria while C4-methyl stanol products (dinosterol) can be synthesized in dinoflagellates and preserved as sterane biomarkers in ancient sedimentary rock is key to eukaryotic sterol evolution. In this regard, nematodes have been proposed to convert dietary cholesterol to 8(14)-lophenol by a secondary metabolism pathway that could involve sterol C4 methylation analogous to the C2 methylation of hopanoids (radicle-type mechanism) or C24 methylation of sterols (carbocation-type mechanism). Here, we characterized dichotomous cholesterol metabolic pathways in Caenorhabditis elegans that generate 3-oxo sterol intermediates in separate paths to lophanol (4-methyl stanol) and 8(14)-lophenol (4-methyl stenol). We uncovered alternate C3-sterol oxidation and Δ7 desaturation steps that regulate sterol flux from which branching metabolite networks arise, while lophanol/8(14)-lophenol formation is shown to be dependent on a sterol C4α-methyltransferse (4-SMT) that requires 3-oxo sterol substrates and catalyzes a newly discovered 3-keto-enol tautomerism mechanism linked to S-adenosyl-l-methionine-dependent methylation. Alignment-specific substrate-binding domains similarly conserved in 4-SMT and 24-SMT enzymes, despite minimal amino acid sequence identity, suggests divergence from a common, primordial ancestor in the evolution of methyl sterols. The combination of these results provides evolutionary leads to sterol diversity and points to cryptic C4-methyl steroidogenic pathways of targeted convergence that mediate lineage-specific adaptations.
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Affiliation(s)
- Wenxu Zhou
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Paxtyn M Fisher
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Boden H Vanderloop
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Yun Shen
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Huazhong Shi
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
| | - Adrian J Maldonado
- Department of Biology, Geology, and Physical Sciences, Sul Ross State University, Alpine, TX
| | - David J Leaver
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX.,Department of Biology, Geology, and Physical Sciences, Sul Ross State University, Alpine, TX
| | - W David Nes
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX
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Pal S, Rastogi S, Nagegowda DA, Gupta MM, Shasany AK, Chanotiya CS. RNAi of Sterol Methyl Transferase1 Reveals its Direct Role in Diverting Intermediates Towards Withanolide/Phytosterol Biosynthesis in Withania somnifera. PLANT & CELL PHYSIOLOGY 2019; 60:672-686. [PMID: 30541044 DOI: 10.1093/pcp/pcy237] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 12/06/2018] [Indexed: 06/09/2023]
Abstract
The medicinal properties of Ashwagandha (Withania somnifera) are accredited to a group of compounds called withanolides. 24-Methylene cholesterol is the intermediate for sterol biosynthesis and a proposed precursor of withanolide biogenesis. However, conversion of 24-methylene cholesterol to withaferin A and other withanolides has not yet been biochemically dissected. Hence, in an effort to fill this gap, an important gene, encoding S-adenosyl l-methionine-dependent sterol-C24-methyltransferase type 1 (SMT1), involved in the first committed step of sterol biosynthesis, from W. somnifera was targeted in the present study. Though SMT1 has been characterized in model plants such as Nicotiana tabacum and Arabidopsis thaliana, its functional role in phytosterol and withanolide biosynthesis was demonstrated for the first time in W. somnifera. Since SMT1 acts at many steps preceding the withanolide precursor, the impact of this gene in channeling of metabolites for withanolide biosynthesis and its regulatory nature was illustrated by suppressing the gene in W. somnifera via the RNA interference (RNAi) approach. Interestingly, down-regulation of SMT1 in W. somnifera led to reduced levels of campesterol, sitosterol and stigmasterol, with an increase of cholesterol content in the transgenic RNAi lines. In contrast, SMT1 overexpression in transgenic N. tabacum enhanced the level of all phytosterols except cholesterol, which was not affected. The results established that SMT1 plays a crucial role in W. somnifera withanolide biosynthesis predominantly through the campesterol and stigmasterol routes.
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Affiliation(s)
- Shaifali Pal
- Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants, PO CIMAP, Lucknow, Uttar Pradesh, India
- Academy of Scientific and Innovative Research, CSIR-Human Resource Development Centre, Postal Staff College Area, Sector-19, Kamla Nehru Nagar, Ghaziabad, Uttar Pradesh, India
| | - Shubhra Rastogi
- Department of Biochemistry, University of Lucknow, Lucknow, Uttar Pradesh, India
| | - Dinesh A Nagegowda
- Molecular Plant Biology and Biotechnology Lab, CSIR-Central Institute of Medicinal and Aromatic Plants Research Centre, Allalasandra, GKVK Post, Bangalore, Karnataka, India
| | - Madan Mohan Gupta
- Analytical Chemistry Division, CSIR-Central Institute of Medicinal and Aromatic Plants, PO CIMAP, Lucknow, Uttar Pradesh, India
| | - Ajit Kumar Shasany
- Biotechnology Division, CSIR-Central Institute of Medicinal and Aromatic Plants, PO CIMAP, Lucknow, Uttar Pradesh, India
- Academy of Scientific and Innovative Research, CSIR-Human Resource Development Centre, Postal Staff College Area, Sector-19, Kamla Nehru Nagar, Ghaziabad, Uttar Pradesh, India
| | - Chandan Singh Chanotiya
- Laboratory of Aromatic Plants and Chiral Separation, Chemical Sciences Division, CSIR-Central Institute of Medicinal and Aromatic Plants (CIMAP), Lucknow, Uttar Pradesh, India
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8
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Zhou W, Debnath A, Jennings G, Hahn HJ, Vanderloop BH, Chaudhuri M, Nes WD, Podust LM. Enzymatic chokepoints and synergistic drug targets in the sterol biosynthesis pathway of Naegleria fowleri. PLoS Pathog 2018; 14:e1007245. [PMID: 30212566 PMCID: PMC6136796 DOI: 10.1371/journal.ppat.1007245] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 07/27/2018] [Indexed: 11/29/2022] Open
Abstract
Naegleria fowleri is a free-living amoeba that can also act as an opportunistic pathogen causing severe brain infection, primary amebic meningoencephalitis (PAM), in humans. The high mortality rate of PAM (exceeding 97%) is attributed to (i) delayed diagnosis, (ii) lack of safe and effective anti-N. fowleri drugs, and (iii) difficulty of delivering drugs to the brain. Our work addresses identification of new molecular targets that may link anti-Naegleria drug discovery to the existing pharmacopeia of brain-penetrant drugs. Using inhibitors with known mechanism of action as molecular probes, we mapped the sterol biosynthesis pathway of N. fowleri by GC-MS analysis of metabolites. Based on this analysis, we chemically validated two enzymes downstream to CYP51, sterol C24-methyltransferase (SMT, ERG6) and sterol Δ8-Δ7 -isomerase (ERG2), as potential therapeutic drug targets in N. fowleri. The sterol biosynthetic cascade in N. fowleri displayed a mixture of canonical features peculiar to different domains of life: lower eukaryotes, plants and vertebrates. In addition to the cycloartenol→ergosterol biosynthetic route, a route leading to de novo cholesterol biosynthesis emerged. Isotopic labeling of the de novo-synthesized sterols by feeding N. gruberi trophozoites on the U13C-glucose-containing growth medium identified an exogenous origin of cholesterol, while 7-dehydrocholesterol (7DHC) had enriched 13C-content, suggesting a dual origin of this metabolite both from de novo biosynthesis and metabolism of scavenged cholesterol. Sterol homeostasis in Naegleria may be orchestrated over the course of its life-cycle by a "switch" between ergosterol and cholesterol biosynthesis. By demonstrating the growth inhibition and synergistic effects of the sterol biosynthesis inhibitors, we validated new, potentially druggable, molecular targets in N. fowleri. The similarity of the Naegleria sterol Δ8-Δ7 -isomerase to the human non-opioid σ1 receptor, implicated in human CNS conditions such as addiction, amnesia, pain and depression, provides an incentive to assess structurally diverse small-molecule brain-penetrant drugs targeting the human receptor for anti-Naegleria activity.
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Affiliation(s)
- Wenxu Zhou
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, United States of America
| | - Anjan Debnath
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Gareth Jennings
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Hye Jee Hahn
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Boden H. Vanderloop
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, United States of America
| | - Minu Chaudhuri
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee, United States of America
| | - W. David Nes
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, United States of America
| | - Larissa M. Podust
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California, United States of America
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9
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Najle SR, Molina MC, Ruiz-Trillo I, Uttaro AD. Sterol metabolism in the filasterean Capsaspora owczarzaki has features that resemble both fungi and animals. Open Biol 2017; 6:rsob.160029. [PMID: 27383626 PMCID: PMC4967820 DOI: 10.1098/rsob.160029] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 06/15/2016] [Indexed: 11/13/2022] Open
Abstract
Sterols are essential for several physiological processes in most eukaryotes. Sterols regulate membrane homeostasis and participate in different signalling pathways not only as precursors of steroid hormones and vitamins, but also through its role in the formation of lipid rafts. Two major types of sterols, cholesterol and ergosterol, have been described so far in the opisthokonts, the clade that comprise animals, fungi and their unicellular relatives. Cholesterol predominates in derived bilaterians, whereas ergosterol is what generally defines fungi. We here characterize, by a combination of bioinformatic and biochemical analyses, the sterol metabolism in the filasterean Capsaspora owczarzaki, a close unicellular relative of animals that is becoming a model organism. We found that C. owczarzaki sterol metabolism combines enzymatic activities that are usually considered either characteristic of fungi or exclusive to metazoans. Moreover, we observe a differential transcriptional regulation of this metabolism across its life cycle. Thus, C. owczarzaki alternates between synthesizing 7-dehydrocholesterol de novo, which happens at the cystic stage, and the partial conversion—via a novel pathway—of incorporated cholesterol into ergosterol, the characteristic fungal sterol, in the filopodial and aggregative stages.
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Affiliation(s)
- Sebastián R Najle
- Instituto de Biología Molecular y Celular de Rosario (IBR) CONICET and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, Rosario S2000FHQ, Argentina Institut de Biologia Evolutiva, CSIC-Universitat Pompeu Fabra, Passeig Marítim de la Barceloneta 37-49, Barcelona 08003, Catalonia, Spain
| | - María Celeste Molina
- Instituto de Biología Molecular y Celular de Rosario (IBR) CONICET and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, Rosario S2000FHQ, Argentina
| | - Iñaki Ruiz-Trillo
- Institut de Biologia Evolutiva, CSIC-Universitat Pompeu Fabra, Passeig Marítim de la Barceloneta 37-49, Barcelona 08003, Catalonia, Spain Departament de Genètica, Universitat de Barcelona, Av. Diagonal, 645, Barcelona 08028, Catalonia, Spain Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, Barcelona 08010, Catalonia, Spain
| | - Antonio D Uttaro
- Instituto de Biología Molecular y Celular de Rosario (IBR) CONICET and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, Rosario S2000FHQ, Argentina
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10
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Konecna A, Toth Hervay N, Valachovic M, Gbelska Y. ERG6 gene deletion modifies Kluyveromyces lactis susceptibility to various growth inhibitors. Yeast 2016; 33:621-632. [PMID: 27668979 DOI: 10.1002/yea.3212] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 09/13/2016] [Accepted: 09/21/2016] [Indexed: 11/09/2022] Open
Abstract
The ERG6 gene encodes an S-adenosylmethionine dependent sterol C-24 methyltransferase in the ergosterol biosynthetic pathway. In this work we report the results of functional analysis of the Kluyveromyces lactis ERG6 gene. We cloned the KlERG6 gene, which was able to complement the erg6Δ mutation in both K. lactis and Saccharomyces cerevisiae. The lack of ergosterol in the Klerg6 deletion mutant was accompanied by increased expression of genes encoding the last steps of the ergosterol biosynthesis pathway as well as the KlPDR5 gene encoding an ABC transporter. The Klerg6Δ mutation resulted in reduced cell susceptibility to amphotericin B, nystatin and pimaricin and increased susceptibility to azole antifungals, fluphenazine, terbinafine, brefeldin A and caffeine. The susceptibility phenotype was suppressed by the KlPDR16 gene encoding one of the phosphatidylinositol transfer proteins belonging to the Sec14 family. Decreased activity of KlPdr5p in Klerg6Δ mutant (measured as the ability to efflux rhodamine 6G) together with increased amount of KlPDR5 mRNA suggest that the zymosterol which accumulates in the Klerg6Δ mutant may not fully compensate for ergosterol in the membrane targeting of efflux pumps. These results point to the fact that defects in sterol transmethylation appear to cause a multitude of physiological effects in K. lactis cells. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Alexandra Konecna
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology and Virology, Bratislava, Slovak Republic
| | - Nora Toth Hervay
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology and Virology, Bratislava, Slovak Republic
| | - Martin Valachovic
- Slovak Academy of Sciences, Institute of Animal Biochemistry and Genetics, Ivanka pri Dunaji, Slovak Republic
| | - Yvetta Gbelska
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Microbiology and Virology, Bratislava, Slovak Republic
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11
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Tengg M, Stecher H, Remler P, Eiteljörg I, Schwab H, Gruber-Khadjawi M. Molecular characterization of the C-methyltransferase NovO of Streptomyces spheroides, a valuable enzyme for performing Friedel–Crafts alkylation. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.molcatb.2012.03.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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12
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Molnár I, Lopez D, Wisecaver JH, Devarenne TP, Weiss TL, Pellegrini M, Hackett JD. Bio-crude transcriptomics: gene discovery and metabolic network reconstruction for the biosynthesis of the terpenome of the hydrocarbon oil-producing green alga, Botryococcus braunii race B (Showa). BMC Genomics 2012; 13:576. [PMID: 23110428 PMCID: PMC3533583 DOI: 10.1186/1471-2164-13-576] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 10/19/2012] [Indexed: 12/16/2022] Open
Abstract
Background Microalgae hold promise for yielding a biofuel feedstock that is sustainable, carbon-neutral, distributed, and only minimally disruptive for the production of food and feed by traditional agriculture. Amongst oleaginous eukaryotic algae, the B race of Botryococcus braunii is unique in that it produces large amounts of liquid hydrocarbons of terpenoid origin. These are comparable to fossil crude oil, and are sequestered outside the cells in a communal extracellular polymeric matrix material. Biosynthetic engineering of terpenoid bio-crude production requires identification of genes and reconstruction of metabolic pathways responsible for production of both hydrocarbons and other metabolites of the alga that compete for photosynthetic carbon and energy. Results A de novo assembly of 1,334,609 next-generation pyrosequencing reads form the Showa strain of the B race of B. braunii yielded a transcriptomic database of 46,422 contigs with an average length of 756 bp. Contigs were annotated with pathway, ontology, and protein domain identifiers. Manual curation allowed the reconstruction of pathways that produce terpenoid liquid hydrocarbons from primary metabolites, and pathways that divert photosynthetic carbon into tetraterpenoid carotenoids, diterpenoids, and the prenyl chains of meroterpenoid quinones and chlorophyll. Inventories of machine-assembled contigs are also presented for reconstructed pathways for the biosynthesis of competing storage compounds including triacylglycerol and starch. Regeneration of S-adenosylmethionine, and the extracellular localization of the hydrocarbon oils by active transport and possibly autophagy are also investigated. Conclusions The construction of an annotated transcriptomic database, publicly available in a web-based data depository and annotation tool, provides a foundation for metabolic pathway and network reconstruction, and facilitates further omics studies in the absence of a genome sequence for the Showa strain of B. braunii, race B. Further, the transcriptome database empowers future biosynthetic engineering approaches for strain improvement and the transfer of desirable traits to heterologous hosts.
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Affiliation(s)
- István Molnár
- Natural Products Center, School of Natural Resources and the Environment, The University of Arizona, Tucson, 85739, USA.
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13
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Köksal M, Chou WKW, Cane DE, Christianson DW. Structure of geranyl diphosphate C-methyltransferase from Streptomyces coelicolor and implications for the mechanism of isoprenoid modification. Biochemistry 2012; 51:3003-10. [PMID: 22455498 DOI: 10.1021/bi300109c] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Geranyl diphosphate C-methyltransferase (GPPMT) from Streptomyces coelicolor A3(2) is the first methyltransferase discovered that modifies an acyclic isoprenoid diphosphate, geranyl diphosphate (GPP), to yield a noncanonical acyclic allylic diphosphate product, 2-methylgeranyl diphosphate, which serves as the substrate for a subsequent cyclization reaction catalyzed by a terpenoid cyclase, methylisoborneol synthase. Here, we report the crystal structures of GPPMT in complex with GPP or the substrate analogue geranyl S-thiolodiphosphate (GSPP) along with S-adenosyl-L-homocysteine in the cofactor binding site, resulting from in situ demethylation of S-adenosyl-L-methionine, at 2.05 or 1.82 Å resolution, respectively. These structures suggest that both GPP and GSPP can undergo catalytic methylation in crystalline GPPMT, followed by dissociation of the isoprenoid product. S-Adenosyl-L-homocysteine remains bound in the active site, however, and does not exchange with a fresh molecule of cofactor S-adenosyl-L-methionine. These structures provide important clues about the molecular mechanism of the reaction, especially with regard to the face of the 2,3 double bond of GPP that is methylated as well as the stabilization of the resulting carbocation intermediate through cation-π interactions.
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Affiliation(s)
- Mustafa Köksal
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104-6323, USA
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14
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Effect of substrate features and mutagenesis of active site tyrosine residues on the reaction course catalysed by Trypanosoma brucei sterol C-24-methyltransferase. Biochem J 2011; 439:413-22. [DOI: 10.1042/bj20110865] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
TbSMT [Trypanosoma brucei 24-SMT (sterol C-24-methyltransferase)] synthesizes an unconventional 24-alkyl sterol product set consisting of Δ24(25)-, Δ24(28)- and Δ25(27)-olefins. The C-methylation reaction requires Si(β)-face C-24-methyl addition coupled to reversible migration of positive charge from C-24 to C-25. The hydride shifts responsible for charge migration in formation of multiple ergostane olefin isomers catalysed by TbSMT were examined by incubation of a series of sterol acceptors paired with AdoMet (S-adenosyl-L-methionine). Results obtained with zymosterol compared with the corresponding 24-2H and 27-13C derivatives revealed isotopic-sensitive branching in the hydride transfer reaction on the path to form a 24-methyl-Δ24(25)-olefin product (kinetic isotope effect, kH/kD=1.20), and stereospecific CH3→CH2 elimination at the C28 branch and C27 cis-terminal methyl to form Δ24(28) and Δ25(27) products respectively. Cholesta-5,7,22,24-tetraenol converted into ergosta-5,7,22,24(28)-tetraenol and 24β–hydroxy ergosta-5,7,23-trienol (new compound), whereas ergosta-5,24-dienol converted into 24-dimethyl ergosta-5,25(27)-dienol and cholesta-5,7,24-trienol converted into ergosta-5,7,25(27)trienol, ergosta-5,7,24(28)-trienol, ergosta-5,7,24-trienol and 24 dimethyl ergosta-5,7,25(27)-trienol. We made use of our prior research and molecular modelling of 24-SMT to identify contact amino acids that might affect catalysis. Conserved tyrosine residues at positions 66, 177 and 208 in TbSMT were replaced with phenylalanine residues. The substitutions generated variable loss of activity during the course of the first C-1-transfer reaction, which differs from the corresponding Erg6p mutants that afforded a gain in C-2-transfer activity. The results show that differences exist among 24-SMTs in control of C-1- and C-2-transfer activities by interactions of intermediate and aromatic residues in the activated complex and provide an opportunity for rational drug design of a parasite enzyme not synthesized by the human host.
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15
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Naturally occurring fatty acid methyl esters and ethyl esters in the green microalga Chlamydomonas reinhardtii. ANN MICROBIOL 2011. [DOI: 10.1007/s13213-011-0361-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022] Open
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16
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Neelakandan AK, Song Z, Wang J, Richards MH, Wu X, Valliyodan B, Nguyen HT, Nes WD. Cloning, functional expression and phylogenetic analysis of plant sterol 24C-methyltransferases involved in sitosterol biosynthesis. PHYTOCHEMISTRY 2009; 70:1982-98. [PMID: 19818974 DOI: 10.1016/j.phytochem.2009.09.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 07/20/2009] [Accepted: 09/03/2009] [Indexed: 05/28/2023]
Abstract
Sterol 24C-methyltransferases (SMTs) constitute a group of sequence-related proteins that catalyze the distinct patterns of 24-alkyl sterols that occur throughout nature. Two SMT cDNAs (SMT2-1 and SMT2-2) were cloned by homology based PCR methods from young leaves of Glycine max (soybean) and the corresponding enzymes were expressed functionally in Escherichia coli. The full-length cDNA for SMT2-1 and SMT2-2 have open reading frames of 1086 bp and 1092 bp, respectively, and encode proteins of 361 and 363 residues with a calculated molecular mass of 40.3 and 40.4 kDa, respectively. The substrate preference of the two isoforms was similar yet they differed from SMT1; kinetically SMT2-1 and SMT2-2 generated k(cat) values for the optimal substrate 24(28)methylene lophenol of 0.8 min(-1) and 1.34 min(-1), respectively, compared to the activity of SMT1 that generated a k(cat) for the optimal substrate cycloartenol of 0.6 min(-1). SMT2-2 was purified to homogeneity and the subunit organization shown to be tetrameric in similar fashion to other cloned SMTs. Analysis of the accumulated products catalyzed by the recombinant enzymes demonstrated that soybean SMT2-1 and SMT2-2 operate transalkylation activities analogous to the soybean plant SMT1. Metabolite analyses correlated with transcript profiling of the three SMT isoforms during soybean maturation clearly demonstrated that SMT isoform expression determines specific C24-methyl to C24-ethyl ratios to flowering whereas with seed development there is a disconnection such that the SMT transcript levels decrease against an increase in sterol content; generally SMT2-2 is expressed more than SMT2-1 or SMT1. These observations suggest that the genes that encode SMT1 and SMT2 in sitosterol biosynthesis may have undergone divergent evolution. In support of this proposition, the genomic organization for SMT1 of fungi and protozoa align very closely with one another and to those of the plant SMT2; both sets of SMTs lack introns. Unexpectedly, the SMT1 from Glycine max and other embryophytes of diverse origin possess disparate intron-exon characteristics that can be shown relates back to the algae. Our results suggest that the order of SMT1 appearing before SMT2 in phytosterol synthesis arose recently in plant evolution in response to duplication of a more primitive SMT gene likely to have been bifunctional and catalytically promiscuous.
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Affiliation(s)
- Anjanasree K Neelakandan
- Division of Plant Sciences and National Center for Soybean Biotechnology, University of Missouri, Columbia, MO 65211, USA
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17
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Liu J, Nes WD. Steroidal triterpenes: design of substrate-based inhibitors of ergosterol and sitosterol synthesis. Molecules 2009; 14:4690-706. [PMID: 19924096 PMCID: PMC6255433 DOI: 10.3390/molecules14114690] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 11/05/2009] [Accepted: 11/10/2009] [Indexed: 11/27/2022] Open
Abstract
This article reviews the design and study, in our own laboratory and others, of new steroidal triterpenes with a modified lanosterol or cycloartenol frame. These compounds, along with a number of known analogs with the cholestane skeleton, have been evaluated as reversible or irreversible inhibitors of sterol C24-methyltransferase (SMT) from plants, fungi and protozoa. The SMT catalyzes the C24-methylation reaction involved with the introduction of the C24-methyl group of ergosterol and the C24-ethyl group of sitosterol, cholesterol surrogates that function as essential membrane inserts in many photosynthetic and non-photosynthetic eukaryotic organisms. Sterol side chains constructed with a nitrogen, sulfur, bromine or fluorine atom, altered to possess a methylene cyclopropane group, or elongated to include terminal double or triple bonds are shown to exhibit different in vitro activities toward the SMT which are mirrored in the inhibition potencies detected in the growth response of treated cultured human and plant cells or microbes. Several of the substrate-based analogs surveyed here appear to be taxaspecific compounds acting as mechanism-based inactivators of the SMT, a crucial enzyme not synthesized by animals. Possible mechanisms for the inactivation process and generation of novel products catalyzed by the variant SMTs are discussed.
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Affiliation(s)
- Jialin Liu
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.
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18
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Renard D, Perruchon J, Giera M, Müller J, Bracher F. Side chain azasteroids and thiasteroids as sterol methyltransferase inhibitors in ergosterol biosynthesis. Bioorg Med Chem 2009; 17:8123-37. [PMID: 19833521 DOI: 10.1016/j.bmc.2009.09.037] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 09/16/2009] [Accepted: 09/18/2009] [Indexed: 10/20/2022]
Abstract
The synthesis of some novel azasteroids and thiasteroids based on a pregnan nucleus with a Delta7 double bond in two to five steps from the key aldehyde (3S,20S)-20-formylpregn-7-en-3-yl acetate has been disclosed herein. These compounds were evaluated as potential inhibitors of the enzyme Delta24-sterol methyltransferase (24-SMT), which is a key enzyme in the biosynthesis of ergosterol, and for their effects on the growth of the yeast Yarrowia lipolytica. Most of the side chain modified analogues were recognized as 24-SMT inhibitors, and in particular the 23-azasteroids 5f-5i and the 24-azasteroid 11 showed potent antifungal activity. The target enzyme could be identified unambiguously using an improved whole-cell assay combined with GC-MS analysis of the sterol pattern resulting upon incubation with the inhibitors.
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Affiliation(s)
- Delphine Renard
- Department Pharmazie-Zentrum für Pharmaforschung, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377 Munich, Germany
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19
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Ge W, Wang S, Shan L, Li N, Liu HM. Transformation of 3β-hydroxy-5-en-steroids by Mucor racemosus. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/j.molcatb.2008.01.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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20
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A nonsense mutation in the ERG6 gene leads to reduced susceptibility to polyenes in a clinical isolate of Candida glabrata. Antimicrob Agents Chemother 2008; 52:3701-9. [PMID: 18694952 DOI: 10.1128/aac.00423-08] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Unlike the molecular mechanisms that lead to azole drug resistance, the molecular mechanisms that lead to polyene resistance are poorly documented, especially in pathogenic yeasts. We investigated the molecular mechanisms responsible for the reduced susceptibility to polyenes of a clinical isolate of Candida glabrata. Sterol content was analyzed by gas-phase chromatography, and we determined the sequences and levels of expression of several genes involved in ergosterol biosynthesis. We also investigated the effects of the mutation harbored by this isolate on the morphology and ultrastructure of the cell, cell viability, and vitality and susceptibility to cell wall-perturbing agents. The isolate had a lower ergosterol content in its membranes than the wild type, and the lower ergosterol content was found to be associated with a nonsense mutation in the ERG6 gene and induction of the ergosterol biosynthesis pathway. Modifications of the cell wall were also seen, accompanied by increased susceptibility to cell wall-perturbing agents. Finally, this mutation, which resulted in a marked fitness cost, was associated with a higher rate of cell mortality. Wild-type properties were restored by complementation of the isolate with a centromeric plasmid containing a wild-type copy of the ERG6 gene. In conclusion, we have identified the molecular event responsible for decreased susceptibility to polyenes in a clinical isolate of C. glabrata. The nonsense mutation detected in the ERG6 gene of this isolate led to a decrease in ergosterol content. This isolate may constitute a useful tool for analysis of the relevance of protein trafficking in the phenomena of azole resistance and pseudohyphal growth.
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21
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Yeast sterol C24-methyltransferase: role of highly conserved tyrosine-81 in catalytic competence studied by site-directed mutagenesis and thermodynamic analysis. Arch Biochem Biophys 2008; 477:313-23. [PMID: 18555004 DOI: 10.1016/j.abb.2008.05.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 05/23/2008] [Accepted: 05/23/2008] [Indexed: 11/22/2022]
Abstract
The role of Try-81 in the reaction catalyzed by Saccharomyces cerevisiae sterol 24-C-methyltransferase (Erg6p) was investigated kinetically and for product differences against a panel of position-81 mutants in which Tyr was substituted with Trp, Phe, Ile, Leu, Val and Ala. The residue chosen for mutation is one that was reported previously to accept fecosterol and yield a set 24-ethyl (idene) sterol products typical of plants, showing the amino acid residue is located close to the transient C25 carbocation intermediate in the active site. One group of mutants (aromatic) tested with the natural substrate zymosterol accelerated the C-methylation reaction (k(cat)/K(m)) whereas the other group of mutants (aliphatics) decreased catalytic competence as the amino acid side chain was downsized. Mutating to aromatic and assaying with the substrate analog designed as a suicide substrate 26,27-dehydrozymosterol favored C26-monol formation, whereas mutating to the aliphatic of smaller size favored C26-diol formation (a measure of enzyme alkylation). In no case was zymosterol converted to an intermediate that formed a C25-diol. Thermodynamic analysis (determination of E(a), DeltaG(double dagger), DeltaH(double dagger) and TDeltaS(double dagger)) for the C-methylation reaction performed by these enzymes assayed with the substrate and its analog or zymosterol paired with the "charged' high energy intermediate (HEI) analogs 24(R,S)25,epiminolanosterol and 25-azalanosterol or "neutral" membrane insert ergosterol showed that mutation to aromatics can reduce inhibitor potency (measured as K(m)/K(i)), yet catalysis can improve in Trp81 by the introduction of a gain in free energy associated with stabilization of the transition state of a rate-controlling step directed toward turnover. Alternatively, mutation to the smaller aliphatic amino acid side chains led to a destabilization in the active site structure which was accompanied by increases in the partition ratios associated with abortive complex formation. The results are explained by consideration of the functional differences attributed to Tyr81 substitution to aromatics and aliphatics of different size involved with cation-pi or hydrogen bonding interactions and in the activation barriers required of differing side chain conformations to orient the reactants in the direction of turnover versus enzyme inactivation.
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22
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Wang J, Liu J, Song Z, Nes WD. Sterol C24-methyltransferase: mechanistic studies of the C-methylation reaction with 24-fluorocycloartenol. Bioorg Med Chem Lett 2008; 18:232-5. [PMID: 17998159 DOI: 10.1016/j.bmcl.2007.10.089] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Revised: 10/21/2007] [Accepted: 10/25/2007] [Indexed: 11/25/2022]
Abstract
The mechanism of the C-methylation reaction was studied with the allylic substrate analog 24-fluorocycloartenol 10 assayed with soybean sterol C24-methyltransferase (SMT). 10 is an effective competitive inhibitor (Ki = 32 microM) of the SMT, and the electron-withdrawing alpha-fluorine substituent was shown to suppress the rate of the C-methylation reaction by one order of magnitude relative to the natural cycloartenol substrate, kcat = 0.02 min(-1) versus 0.6 min(-1); alternately 10 can prevent the critical hydride shift of H24 to C25 to afford time-dependent inactivation of SMT (k(inact) = 0.32 min(-1)).
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Affiliation(s)
- Junqing Wang
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
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23
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Plant Sterol Methyltransferases: Phytosterolomic Analysis, Enzymology, and Bioengineering Strategies. BIOENGINEERING AND MOLECULAR BIOLOGY OF PLANT PATHWAYS 2008. [DOI: 10.1016/s1755-0408(07)01009-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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24
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Song Z, Nes WD. Sterol Biosynthesis Inhibitors: Potential for Transition State Analogs and Mechanism‐Based Inactivators Targeted at Sterol Methyltransferase. Lipids 2007; 42:15-33. [PMID: 17393207 DOI: 10.1007/s11745-006-3017-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Accepted: 12/15/2006] [Indexed: 11/28/2022]
Abstract
Sterol biosynthesis inhibitors (SBIs), discovered in the late 1960s and subsequently used commercially to treat ergosterol-dependent fungal diseases, represent a unique drug class targeted at an enzyme in a biosynthetic pathway. To date, few drugs have been commercialized as enzyme inhibitors; yet, prescription of SBIs has emerged as the gold standard for some cases of non-life-threatening antifungal chemotherapy and in crop protection. SBIs are not designed for their structural resemblance to the sterol molecule; they nonetheless can engender a curative effect by interfering with sterol production and homeostasis in the pathogenic organism. The increased use of SBIs in recent years, particularly the azole antifungals, has resulted in the development of resistance to those drugs, necessitating additional work to further our understanding of antifungal resistance and to explore opportunities to develop new enzyme inhibitors and uncover new enzyme targets that can regulate carbon flux in the post-lanosterol/cycloartenol pathway. This article reports general considerations for enzyme mechanism and active-site probes using inhibitors of the C-methylation reaction, including a potential new class of antifungal/antiparasitic agents of phytosterol synthesis tailored as mechanism-based inactivators. These steroid-based compounds prepared with different sterol side chain functionalities are designed to reversibly or irreversibly impair the sterol methyltransferase, an enzyme expressed in pathogenic microbes and plants but not in the human host. The salient aspects of these and related topics directed toward the enzyme recognition of sterol structure, and the inhibitory properties and catalytic competence of a series of specifically modified substrate analogs that affect sterol methyltransferase action are discussed.
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Affiliation(s)
- Zhihong Song
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
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25
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Mysyakina IS, Funtikova NS. The role of sterols in morphogenetic processes and dimorphism in fungi. Microbiology (Reading) 2007. [DOI: 10.1134/s0026261707010018] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Abstract
Many biotransformations of mid- to long chain fatty acyl derivatives are intrinsically interesting because of their high selectivity and novel mechanisms. These include one carbon transfer, hydration, isomerization, hydrogenation, ladderane and hydrocarbon formation, thiolation and various oxidative transformations such as epoxidation, hydroxylation and desaturation. In addition, hydroperoxidation of polyunsaturated fatty acids leads to a diverse array of bioactive compounds. The bioorganic aspects of selected reactions will be highlighted in this review; 210 references are cited.
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Affiliation(s)
- Peter H Buist
- Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6
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Nes WD, Sinha A, Jayasimha P, Zhou W, Song Z, Dennis AL. Probing the sterol binding site of soybean sterol methyltransferase by site-directed mutagenesis: functional analysis of conserved aromatic amino acids in Region 1. Arch Biochem Biophys 2006; 448:23-30. [PMID: 16271698 DOI: 10.1016/j.abb.2005.08.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Revised: 08/09/2005] [Accepted: 08/30/2005] [Indexed: 11/22/2022]
Abstract
Soybean sterol methyltransferase (SMT) in the presence of AdoMet catalyzes the transmethylation of the delta24-bond of the sterol side chain to produce phytosterols with a methyl(lene) or ethyl(idene) group at C-24. The function of six aromatic amino acids associated with the putative active center of the SMT, i.e., Region 1 that extends from Phe82 to Phe93 in soybean SMT, was studied by site-directed mutagenesis and heterologous expression in BL21(DE3) bacterial cells. The enzyme-generated products were characterized kinetically and by GC-MS analysis. Substitution of the aromatic amino acids at positions 82, 83, 85, 87, 91, and 93 with a leucine residue produced mutant SMTs with varying activities. The mutants converted cycloartenol to 24(28)-methylene cycloartanol [C1-activity] from a few percent to as much as 95% of the control activity. In contrast, none of the leucine mutants were found to catalyze 24(28)-methylene lophenol [C2-activity], suggesting a loss of function associated with the second C1-transfer activity. In contrast to the loss of the second C1-transfer activity of the Phe82Leu, replacement of the Phe82 residue to isoleucine had minimal effect on the first or second C1-transfer activities, suggesting that the increased bulk (branching) in the leucine side chain contributes to significant perturbations in the active site that generate inaccurate positioning of the substrate side chain disfavoring the second C1-transfer activity. Replacement of Tyr83 to phenylalanine resulted in an increase of the specificity constant (kcat/Km) for the substrate of the second C1-transfer activity by a factor of 5 compared to control and an increase of delta24(28)Z-ethylidene sterol formation in the 24-ethyl sterol product set, suggesting that loss of steric bulk from the phenolic hydroxyl group on tyrosine generates a less precise fit of the delta24(28) sterol side chain into the active site favoring the second C1-transfer activity and prompting reaction channeling during catalysis. Circular dichroism spectra, equilibrium dialysis studies of AdoMet, and chromatographic information of the wild-type and Tyr83 mutants confirmed retention of the overall conformation of the enzyme during the experiments. Together, these findings suggest that the amino acids of Region 1 provide a tight substrate orientation imposed by hydrophobic interactions between the sterol side chain and the SMT active site contacts and control the production and processing of the transmethylation pathways governed by the first and second C1-transfer activities.
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Affiliation(s)
- W David Nes
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
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Zhou W, Lepesheva GI, Waterman MR, Nes WD. Mechanistic analysis of a multiple product sterol methyltransferase implicated in ergosterol biosynthesis in Trypanosoma brucei. J Biol Chem 2006; 281:6290-6. [PMID: 16414960 DOI: 10.1074/jbc.m511749200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sterol methyltransferase (SMT) plays a key role in sterol biosynthesis in different pathogenic organisms by setting the pattern of the side chain structure of the final product. This catalyst, absent in humans, provides critical pathway-specific enzymatic steps in the production of ergosterol in fungi or phytosterols in plants. The new SMT gene was isolated from Trypanosoma brucei genomic DNA and cloned into an Escherichia coli expression system. The recombinant SMT was purified to homogeneity to give a band at 40.0 kDa upon SDS-PAGE and showed a tetrameric subunit organization by gel chromatography. It has a pH optimum of 7.5, an apparent kcat value of 0.01 s(-1), and a Km of 47 +/- 4 microm for zymosterol. The products of the reaction were a mixture of C24-monoalkylated sterols, ergosta-8,24 (25)-dienol, ergosta-8,25 (27)-dienol, and ergosta-8,24 (28)-dienol (fecosterol), and an unusual double C24-alkylated sterol, 24,24-dimethyl ergosta-8,25 (27)-dienol, typically found in plants. Inhibitory profile studies with 25-azalanosterol (Ki value of 39 nm) or 24(R,S), 25-epiminolanosterol (Ki value of 49 nm), ergosterol (Ki value of 27 microm) and 26,27-dehydrozymosterol (Ki and kinact values of 29 microm and 0.26 min(-1), respectively) and data showing zymosterol as the preferred acceptor strongly suggest that the protozoan SMT has an active site topography combining properties of the SMT1 from plants and yeast (37-47% identity). The enzymatic activation of this and other SMTs reveals that the catalytic requirements for the C-methyl reaction are remarkably versatile, whereas the inhibition studies provide a powerful approach to rational design of new anti-sleeping sickness chemotherapeutic drugs.
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Affiliation(s)
- Wenxu Zhou
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1064, USA
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Engineering Pathway Enzymes to Understand the Function and Evolution of Sterol Structure and Activity. RECENT ADVANCES IN PHYTOCHEMISTRY 2006. [DOI: 10.1016/s0079-9920(06)80043-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Enzyme redesign and interactions of substrate analogues with sterol methyltransferase to understand phytosterol diversity, reaction mechanism and the nature of the active site. Biochem Soc Trans 2005. [DOI: 10.1042/bst0331189] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Several STM (sterol methyltransferase) genes have been cloned, sequenced and expressed in bacteria recently, making it possible to address questions of the relationship between sterol structure and function. The active site and mechanism of action of a set of phylogenetically diverse SMTs have been probed by site-directed mutagenesis as well as by using substrate and related analogues of the SMT-catalysed reaction. An active-site model has been developed that is in accord with the results presented, which is consistent with the hypothesis that SMTs are bifunctional enzymes kinetically responsible to bind Δ24-acceptor sterols of specific steric and electronic character and rigid orientation imposed by multiple hydrophobic active site contacts exacted from a common waxy core. Functional divergence influenced by the architectural role of sterols in membranes is considered to govern the evolution of product distribution and specificity of individual SMTs as discussed.
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Abstract
Isoprenoids represent the oldest class of known low molecular-mass natural products synthesized by plants. Their biogenesis in plastids, mitochondria and the endoplasmic reticulum-cytosol proceed invariably from the C5 building blocks, isopentenyl diphosphate and/or dimethylallyl diphosphate according to complex and reiterated mechanisms. Compounds derived from the pathway exhibit a diverse spectrum of biological functions. This review centers on advances obtained in the field based on combined use of biochemical, molecular biology and genetic approaches. The function and evolutionary implications of this metabolism are discussed in relation with seminal informations gathered from distantly but related organisms.
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Affiliation(s)
- Florence Bouvier
- Institut de Biologie Moléculaire des Plantes du CNRS (UPR2357) et Université Louis Pasteur, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France
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Kanagasabai R, Zhou W, Liu J, Nguyen TTM, Veeramachaneni P, Nes WD. Disruption of ergosterol biosynthesis, growth, and the morphological transition inCandida albicansby sterol methyltransferase inhibitors containing sulfur at C-25 in the sterol side chain. Lipids 2004; 39:737-46. [PMID: 15638241 DOI: 10.1007/s11745-004-1290-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The sterol substrate analog 25-thialanosterol and its corresponding sulfonium salt were evaluated for their ability to serve as antifungal agents and to inhibit sterol methyltransferase (SMT) activity in Candida albicans. Both compounds inhibited cell proliferation, were fungistatic, interrupted the yeast-like-form to germ-tube-form transition, and resulted in the accumulation of zymosterol and related delta24-sterols concurrent with a decrease in ergosterol, as was expected for the specific inhibition of SMT activity. Feedback on sterol synthesis was evidenced by elevated levels of cellular sterols in treated vs. control cultures. However, neither farnesol nor squalene accumulated in significant amounts in treated cultures, suggesting that carbon flux is channeled from the isoprenoid pathway to the sterol pathway with minor interruption or redirection until blockage at the C-methylation step. Activity assays using solubilized C. albicans SMT confirmed the inhibitors impair SMT action. Kinetic analysis indicated that 25-thialanosterol inhibited SMT with the properties of a time-dependent mechanism-based inactivator Ki of 5 microM and apparent kinact of 0.013 min(-1), whereas the corresponding sulfonium salt was a reversible-type transition state analog exhibiting a Ki of 20 nM. The results are interpreted to imply changes in ergosterol homeostasis as influenced by SMT activity can control growth and the morphological transition in C. albicans, possibly affecting disease development.
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Affiliation(s)
- Ragu Kanagasabai
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA
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Abstract
Expression of the Arabidopsis sterol methyltransferase2 (SMT2) cDNA in Escherichia coli yields a native protein, when purified to homogeneity, has the predicted molecular mass ca. 40 kDa on SDS-PAGE and recognizes native sterols synthesized by Arabidopsis with a Delta(24(25))-bond (cycloartenol; K(m) 35 microM and k(cat) 0.001s(-1)) and Delta(24(28))-bond (24(28)-methylenelophenol; K(m) 28 microM and k(cat) 0.01 s(-1)). Cycloartenol was converted to a single olefinic product-24(28)-methylenecycloartanol whereas 24(28)-methylenelophenol was converted to a mixture of three stereochemically related products with the Delta(24(28))Z-ethylidene, Delta(24(28))E-ethylidene, and Delta(25(27))-24 beta-ethyl side chains. Structural determinants essential to activity were the nucleophilic features at C-3 and C-24. The double bond position in the sterol substrate influenced catalytic efficiency according to the order: side chain, Delta(24(24))<Delta(24(28)) and nucleus, Delta(7)<Delta(8)<Delta(5)=9,19-cyclopropane. The 14 alpha-methyl group was harmful to catalysis, reducing the suitability of cycloartenol as a substrate. On the basis of substrate activity and product distribution, SMT action was probed further using substrate (26,27-dehydrozymosterol: 26,27-DHZ) and intermediate (25-azacycloartenol: 25-AC) analogs of the SMT-catalyzed reactions. 26,27-DHZ was C-methylated to 26-homocholesta-8(9), 23(24)E, 26(26('))-trienol as well as 26-homocholesta-8(9),26(26')-3 beta,24 beta-dienol by SMT2, K(m) of 15 microM, k(cat) of 0.001 s(-1). In addition, 26,27-DHZ acted as a mechanism-based irreversible inhibitor that results in the specific covalent modification of SMT2, exhibiting K(i) of 49 microM, k(inact) of 0.009 s(-1) and partition ratio of 0.11. Substrate protection with zymosterol, 24(28)-methylenelophenol against 26,27-DHZ and similar inhibition of the first and second C(1)-transfer activities by the reversible inhibitor 25-AC of K(i) 20 nM suggested the analogs interacted at the same active site. [28E-2H]- and [28Z-2H]24(28)-methylenelanosterols were paired with AdoMet and differences of 2H-incorporation in the enzyme-generated 24-ethyl olefins supported an antimechanism. The results suggest plant SMT2 has a position-specific substrate specificity for Delta(24(25))-sterols and contains a single active center to catalyze the consecutive C(1)-transfer activities by substrate reaction channels similar to the fungal SMT1.
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Affiliation(s)
- Wenxu Zhou
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
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24-Thiacycloartanol, a potent mechanism-based inactivator of plant sterol methyltransferase. Tetrahedron Lett 2004. [DOI: 10.1016/j.tetlet.2003.10.203] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Abstract
In recent years, the impressive development of molecular genetics tools, the sequencing of the Arabidopsis thaliana genome, the availability of DNA or transposon tagged mutants, and the multiple possibilities offered by stable transformation with DNA in sense and antisense orientation have enabled the application of a strategy of gain or loss of function to study the sterol biosynthesis pathway. Here we describe the results obtained with these techniques. The results essentially confirm data obtained previously with sterol biosynthesis inhibitors (SBIs) and enable the precise dissection of biosynthetic pathways. We discuss the advantages and disadvantages of molecular genetics techniques as applied to sterol metabolism. The greater selectivity of these techniques constitutes an invaluable advantage and has led to the discovery of a role for sterols in plant development.
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Affiliation(s)
- Pierre Benveniste
- Institut de Biologie Moleculaire des Plantes, Departement Biogenese et Fonctions des Isoprenoides, UPR-CNRS 2357, 28 rue Goethe, 67083 Strasbourg, France.
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Abstract
The mechanisms by which sterol methyl transferases (SMT) transform olefins into structurally different C-methylated products are complex, prompting over 50 years of intense research. Recent enzymological studies, together with the latest discoveries in the fossil record, functional analyses and gene cloning, establish new insights into the enzymatic mechanisms of sterol C-methylation and form a basis for understanding regulation and evolution of the sterol pathway. These studies suggest that SMTs, originated shortly after life appeared on planet earth. SMTs, including those which ultimately give rise to 24 alpha- and 24 beta-alkyl sterols, align the si(beta)-face pi-electrons of the Delta(24)-double bond with the S-methyl group of AdoMet relative to a set of deprotonation bases in the active site. From the orientation of the conformationally flexible side chain in the SMT Michaelis complex, it has been found that either a single product is formed or cationic intermediates are partitioned into multiple olefins. The product structure and stereochemistry of SMT action is phylogenetically distinct and physiologically significant. SMTs control phytosterol homeostasis and their activity is subject to feedback regulation by specific sterol inserts in the membrane. A unified conceptual framework has been formulated in the steric-electric plug model that posits SMT substrate acceptability on the generation of single or double 24-alkylated side chains, which is the basis for binding order, stereospecificity and product diversity in this class of AdoMet-dependent methyl transferase enzymes. The focus of this review is the mechanism of the C-methylation process which, as discussed, can be altered by point mutations in the enzyme to direct the shape of sterol structure to optimize function.
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Affiliation(s)
- W David Nes
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
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