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Abstract
Abstract
Cytochrome P450s belong to a superfamily of enzymes that catalyse a wide variety of oxidative transformations. Hydroxylation is one the most thoroughly investigated of all identified P450-catalysed reactions whilst dehydrogenation has been relatively much less explored to date. P450-catalysed dehydrogenation is often found to occur with hydroxylation and thus, it was initially suspected to be a stepwise process consisting of hydroxylation and subsequent dehydration to yield the final olefin product. This theory has been proven to be invalid and the olefin was shown to be the direct product of a P450-catalysed reaction. This interesting reaction plays a vital role in the metabolism of xenobiotics and the biosynthesis of endogenous compounds, including a number of steroids. A number of well-known examples of P450 mediated dehydrogenation, including those in the metabolism of valproic acid, capsaicin and 3-methylindole and those in the biosynthesis of plant and fungal sterols are discussed in this review.
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2
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Ortiz de Montellano PR, Nelson SD. Rearrangement reactions catalyzed by cytochrome P450s. Arch Biochem Biophys 2011; 507:95-110. [PMID: 20971058 PMCID: PMC3039701 DOI: 10.1016/j.abb.2010.10.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 10/15/2010] [Accepted: 10/18/2010] [Indexed: 12/01/2022]
Abstract
Cytochrome P450s promote a variety of rearrangement reactions both as a consequence of the nature of the radical and other intermediates generated during catalysis, and of the neighboring structures in the substrate that can interact either with the initial radical intermediates or with further downstream products of the reactions. This article will review several kinds of previously published cytochrome P450-catalyzed rearrangement reactions, including changes in stereochemistry, radical clock reactions, allylic rearrangements, "NIH" and related shifts, ring contractions and expansions, and cyclizations that result from neighboring group interactions. Although most of these reactions can be carried out by many members of the cytochrome P450 superfamily, some have only been observed with select P450s, including some reactions that are catalyzed by specific endoperoxidases and cytochrome P450s found in plants.
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Affiliation(s)
- Paul R. Ortiz de Montellano
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA 94158-2517, USA
| | - Sidney D. Nelson
- Department of Medicinal Chemistry, Box 357610, University of Washington, Seattle, WA 98195-7610, USA
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Matuo MCS, Kikuchi IS, Pinto TDJA. Evaluation of cytochrome P-450 concentration in Saccharomyces cerevisiae strains. BRAZ J PHARM SCI 2010. [DOI: 10.1590/s1984-82502010000300011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Saccharomyces cerevisiae has been widely used in mutagenicity tests due to the presence of a cytochrome P-450 system, capable of metabolizing promutagens to active mutagens. There are a large number of S. cerevisiae strains with varying abilities to produce cytochrome P-450. However, strain selection and ideal cultivation conditions are not well defined. We compared cytochrome P-450 levels in four different S. cerevisiae strains and evaluated the cultivation conditions necessary to obtain the highest levels. The amount of cytochrome P-450 produced by each strain varied, as did the incubation time needed to reach the maximum level. The highest cytochrome P-450 concentrations were found in media containing fermentable sugars. The NCYC 240 strain produced the highest level of cytochrome P-450 when grown in the presence of 20 % (w/v) glucose. The addition of ethanol to the media also increased cytochrome P-450 synthesis in this strain. These results indicate cultivation conditions must be specific and well-established for the strain selected in order to assure high cytochrome P-450 levels and reliable mutagenicity results.
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4
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Whitaker BD, Gapper NE. Ripening-Specific Stigmasterol Increase in Tomato Fruit Is Associated with Increased Sterol C-22 Desaturase ( CYP710A11) Gene Expression. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2008; 56:3828-35. [PMID: 0 DOI: 10.1021/jf7037983] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Affiliation(s)
- Bruce D. Whitaker
- Produce Quality and Safety Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705, and Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, New York 14853
| | - Nigel E. Gapper
- Produce Quality and Safety Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705, and Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, New York 14853
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5
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Sisler HD, Ragsdale NN, Waterfield WF. Biochemical aspects of the fungitoxic and growth regulatory action of fenarimol and other pyrimidin-5-ylmethanols. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/ps.2780150208] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Influence of oxygen addition during growth phase on the biosynthesis of lipids in Saccharomyces cerevisiae (M(3)30-9) in enological fermentations. J Biosci Bioeng 2005; 92:33-8. [PMID: 16233054 DOI: 10.1263/jbb.92.33] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2000] [Accepted: 04/09/2001] [Indexed: 11/17/2022]
Abstract
The fatty acid, phospholipid and sterol composition of one strain of Saccharomyces cerevisiae under different oxygen levels during grape must fermentation was studied. Anaerobiosis partially inhibited yeast growth and resulted in a drop in the unsaturation index of the fatty acids throughout the fermentation, as well as an abnormally low ergosterol/phospholipid ratio. Aeration after 48 h of fermentation in anaerobiosis stimulated growth and increased cellular viability, as well as raised the unsaturation index of fatty acids. Although the ergosterol/phospholipid ratio remained low in the days following the aeration, by the end of the fermentation the value was that considered optimum for the maintenance of membrane functions.
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Nusblat AD, Muñoz L, Valcarce GA, Nudel CB. Characterization and properties of cholesterol desaturases from the ciliate Tetrahymena thermophila. J Eukaryot Microbiol 2005; 52:61-7. [PMID: 15702982 DOI: 10.1111/j.1550-7408.2005.3279rr.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Live Tetrahymena thermophila transforms exogenous cholesterol into 7,22-bis, dehydrocholesterol (DHC) by desaturation at positions C7(8) and C22(23) of the cholesterol moiety. In this first report on expression, isolation, characterization, and reconstitution of Tetrahymena's cholesterol desaturases in cell-free extracts, we describe conditions for increasing the expression of both desaturases based on the addition of specific sterols to the culture medium. Reactions performed in vitro, with isolated microsomes, yield only the mono-unsaturated derivatives, 7-DHC and/or 22-DHC. However, selectivity towards one product can be improved with the addition of specific compounds: beta-mercaptoethanol inhibited C22(23) desaturase activity completely, while ethanol selectively increased this activity. Detergent-solubilized microsomes showed no desaturase activity, but partial restoration could be achieved with addition of dilauroyl-phosphatidylcholine liposomes (25%). Both cholesterol desaturases require molecular oxygen and cytochrome b(5). NADH or NADPH can serve as reduced cofactors, albeit with different efficiency, delivered by reductases present in the microsomal fraction. Azide and cyanide, but not azole compounds, inhibited these desaturases, suggesting a key role for cytochrome b(5) in these reactions.
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Affiliation(s)
- Alejandro D Nusblat
- Cátedra de Biotecnología y Microbiología Industrial, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 1113 Buenos Aires, Argentina
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9
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Rogers KM, Pierson CA, Culbertson NT, Mo C, Sturm AM, Eckstein J, Barbuch R, Lees ND, Bard M. Disruption of the Candida albicans CYB5 gene results in increased azole sensitivity. Antimicrob Agents Chemother 2004; 48:3425-35. [PMID: 15328107 PMCID: PMC514794 DOI: 10.1128/aac.48.9.3425-3435.2004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sterol synthesis in fungi is an aerobic process requiring molecular oxygen and, for several cytochrome-mediated reactions, aerobically synthesized heme. Cytochrome b(5) is required for sterol C5-6 desaturation and the encoding gene, CYB5, is nonessential in Saccharomyces cerevisiae. Cyb5p and Ncp1p (cytochrome P-450 reductase) appear to have overlapping functions in this organism, with disruptions of each alone being viable. The cytochrome P-450 reductase phenotype has also been shown to demonstrate increased sensitivity to azole antifungals. Based on this phenotype, the CYB5 gene in the human pathogen Candida albicans was investigated to determine whether the cyb5 genotype was viable and would also demonstrate azole sensitivity. Sequential disruption of the CYB5 alleles by direct transformation resulted in viability, presumably conferred by the presence of a third copy of the CYB5 gene. Subsequent disruption procedures with a pMAL2-CYB5 rescue cassette and a CYB5-URA3 blaster cassette resulted in viable cyb5 strains with no third copy. The C. albicans CYB5 gene is concluded to be nonessential. Thus, the essentiality of this gene and whether we observed two or three alleles was dependent upon the gene disruption protocol. The C. albicans cyb5 strains produced a sterol profile containing low ergosterol levels and sterol intermediates similar to that reported for the S. cerevisiae cyb5. The C. albicans cyb5 shows increased sensitivity to azoles and terbinafine, an inhibitor of squalene epoxidase, and, unexpectedly, increased resistance to morpholines, which inhibit the ERG2 and ERG24 gene products. These results indicate that an inhibitor of Cyb5p would not be lethal but would make the cell significantly more sensitive to azole treatment.
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Affiliation(s)
- K M Rogers
- Department of Biology, Indiana University Purdue University Indianapolis, West Michigan St., Indianapolis, IN 46202-5132, USA
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Kelly SL, Lamb DC, Jackson CJ, Warrilow AG, Kelly DE. The biodiversity of microbial cytochromes P450. Adv Microb Physiol 2003; 47:131-86. [PMID: 14560664 DOI: 10.1016/s0065-2911(03)47003-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The cytochrome P450 (CYP) superfamily of genes and proteins are well known for their involvement in pharmacology and toxicology, but also increasingly for their importance and diversity in microbes. The extent of diversity has only recently become apparent with the emergence of data from whole genome sequencing projects and the coming years will reveal even more information on the diversity in microbial eukaryotes. This review seeks to describe the historical development of these studies and to highlight the importance of the genes and proteins. CYPs are deeply involved in the development of strategies for deterrence and attraction as well as detoxification. As such, there is intense interest in pathways of secondary metabolism that include CYPs in oxidative tailoring of antibiotics, sometimes influencing potency as bioactive compounds. Further to this is interest in CYPs in metabolism of xenobiotics for use as carbon sources for microbial growth and as biotransformation agents or in bioremediation. CYPs are also current and potential drug targets; compounds inhibiting CYP are antifungal and anti-protozoan agents, and potentially similar compounds may be useful against some bacterial diseases such as tuberculosis. Of note is the diversity of CYP requirements within an organism, ranging from Escherichia coli that has no CYPs as in many bacteria, to Mycobacterium smegmatis that has 40 representing 1% of coding genes. The basidiomycete fungus Phanerochaete chrysosporium surprised all when it was found to contain a hundred or more CYPs. The functional genomic investigation of these orphan CYPs is a major challenge for the future.
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Affiliation(s)
- Steven L Kelly
- Wolfson Laboratory of P450 Biodiversity, Institute of Biological Sciences, University of Wales Aberystwyth, Aberystwyth, Wales, UK
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Wessjohann LA, Brandt W, Thiemann T. Biosynthesis and metabolism of cyclopropane rings in natural compounds. Chem Rev 2003; 103:1625-48. [PMID: 12683792 DOI: 10.1021/cr0100188] [Citation(s) in RCA: 477] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ludger A Wessjohann
- Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany.
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12
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Abstract
The essay examines the evidence upon which the presently accepted version of the mechanism of the cytochrome P450(scc)-catalyzed-cleavage of the sidechain of cholesterol is based. This analysis indicates that the generally held view of the process (two consecutive hydroxylations, followed by cleavage of the resulting glycol) most likely does not describe the true mechanism. The available evidence can not be used to support this traditional notion. Two alternative hypotheses are proposed.
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Affiliation(s)
- S Lieberman
- Department of Obstetrics and Gynecology, Institute for Health Sciences, St. Luke's-Roosevelt Hospital Center, 432W 58th Street, New York, NY 10019, USA.
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Valero E, Millán C, Ortega J. Influence of oxygen addition during growth phase on the biosynthesis of lipids in Saccharomyces cerevisiae (M330-9) in enological fermentations. J Biosci Bioeng 2001. [DOI: 10.1016/s1389-1723(01)80195-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Arnoldi A, Carzaniga R, Morini G, Merlini L, Farina G. Synthesis, fungicidal activity, and QSAR of a series of 2-dichlorophenyl-3-triazolylpropyl ethers. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2000; 48:2547-2555. [PMID: 10888582 DOI: 10.1021/jf9906432] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A series of new alkyl and arylalkyl ethers of 2-(2, 4-dichlorophenyl)-3-(1H-1,2,4-triazol-1-yl)propanol, related to the fungicide tetraconazole, were synthesized and tested in vitro or in vivo against seven common pathogens in comparison with tetraconazole. In vitro, most of them exhibited a broad spectrum of activity and an efficacy of the same order of magnitude of the standard, but the activity was influenced by the nature of the substituents. A QSAR study showed that lipophilicity is a major positive parameter in affecting the activity; the second relevant parameter is mu, whereas geometrical descriptors indicate that linear and narrow substituents are more suitable than wide ones. In in vivo assays some compounds had good activity on bean rust, either protective or curative. Sterol analysis showed that the mechanism of action is due to inhibition of 14alpha-demethylase.
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Affiliation(s)
- A Arnoldi
- Dipartimento di Scienze Molecolari Agroalimentari and Istituto di Patologia Vegetale, Università di Milano, Italy.
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Lamb D, Kelly D, Kelly S. Molecular aspects of azole antifungal action and resistance. Drug Resist Updat 1999; 2:390-402. [PMID: 11498355 DOI: 10.1054/drup.1999.0112] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
During the past three decades azole compounds have been developed as medical and agricultural agents to combat fungal diseases. During the 1980s they were introduced as orally active compounds in medicine and the number of such azole drugs is likely to expand in the near future. They represent a successful strategy for antifungal development, but as the incidence of fungal infection has increased coupled to prolonged use of the drugs, the (almost) inevitable emergence of resistance has occurred. This was after resistance had already been encountered as a serious problem in the field, where a larger number of azole fungicides had been employed commercially. In this review the molecular basis of how azoles work is discussed together with how fungi overcome the inhibitory effect of these compounds: through alterations in the primary target molecule (cytochrome P45051; Erg11p; sterol 14alpha-demethylase); through drug efflux mechanisms and through a suppressor mechanism allowing growth on 14-methylated sterols. Copyright 1999 Harcourt Publishers Ltd.
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Affiliation(s)
- David Lamb
- Cytochrome P450 Research Group, AberBiocentre, Edward Llwyd Building, University of Wales Aberystwyth, Aberystwyth, SY23 3DA, Wales, UK
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Lamb DC, Maspahy S, Kelly DE, Manning NJ, Geber A, Bennett JE, Kelly SL. Purification, reconstitution, and inhibition of cytochrome P-450 sterol delta22-desaturase from the pathogenic fungus Candida glabrata. Antimicrob Agents Chemother 1999; 43:1725-8. [PMID: 10390230 PMCID: PMC89351 DOI: 10.1128/aac.43.7.1725] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sterol delta22-desaturase has been purified from a strain of Candida glabrata with a disruption in the gene encoding sterol 14alpha-demethylase (cytochrome P-45051; CYP51). The purified cytochrome P-450 exhibited sterol delta22-desaturase activity in a reconstituted system with NADPH-cytochrome P-450 reductase in dilaurylphosphatidylcholine, with the enzyme kinetic studies revealing a Km for ergosta-5,7-dienol of 12.5 microM and a Vmax of 0. 59 nmol of this substrate metabolized/min/nmol of P-450. This enzyme is encoded by CYP61 (ERG5) in Saccharomyces cerevisiae, and homologues have been shown in the Candida albicans and Schizosaccharomyces pombe genome projects. Ketoconazole, itraconazole, and fluconazole formed low-spin complexes with the ferric cytochrome and exhibited type II spectra, which are indicative of an interaction between the azole moiety and the cytochrome heme. The azole antifungal compounds inhibited reconstituted sterol delta22-desaturase activity by binding to the cytochrome with a one-to-one stoichiometry, with total inhibition of enzyme activity occurring when equimolar amounts of azole and cytochrome P-450 were added. These results reveal the potential for sterol delta22-desaturase to be an antifungal target and to contribute to the binding of drugs within the fungal cell.
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Affiliation(s)
- D C Lamb
- Institute of Biological Sciences, University of Wales Aberystwyth, Aberystwyth, Wales SY23 3DA, England S10 2UH, United Kingdom
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Abstract
The article gives an overview on the history of the discovery of P450 cytochromes and on their occurrence in nature, especially on their interactions with metabolic pathways in fungi. The significance of the P450 cytochromes in the ergosterol synthesis as well as in the inhibitory mechanisms caused by imidazole and triazole antimycotics is described in detail.
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Affiliation(s)
- H Vanden Bossche
- Department of Anti-infectives Research, Janssen Research Foundation, Beerse, Belgium
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Kelly SL, Lamb DC, Baldwin BC, Corran AJ, Kelly DE. Characterization of Saccharomyces cerevisiae CYP61, sterol delta22-desaturase, and inhibition by azole antifungal agents. J Biol Chem 1997; 272:9986-8. [PMID: 9092539 DOI: 10.1074/jbc.272.15.9986] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Cytochrome P-45061 (CYP61) was a cytochrome P-450 revealed during the yeast genome project when chromosome XIII was sequenced. Here we report on the properties of this second microsomal P-450 of vegetatively growing yeast. The enzyme kinetics associated with its endogenous role in sterol Delta22-desaturation revealed a Km of 20.4 microM and a Vmax of 2.9nmol/min/nmol CYP61. The affinity of the enzyme for antifungal drugs was characterized to investigate its potential role in determining tolerance to these sterol 14alpha-demethylase (CYP51) inhibitors. Drug binding induced a type II spectral change, which became saturated at equimolar concentrations of azole drug and P-450. Fluconazole exhibited slightly reduced affinity in comparison to ketoconazole as indicated by carbon monoxide displacement. These and Ki determination for fluconazole (0.14 nM) revealed CYP61 to have a similar affinity to azole drugs when compared with data available for CYP51, and the implications for antifungal treatment were considered.
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Affiliation(s)
- S L Kelly
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, Sheffield University, Sheffield, S10 2UH, United Kingdom.
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Skaggs BA, Alexander JF, Pierson CA, Schweitzer KS, Chun KT, Koegel C, Barbuch R, Bard M. Cloning and characterization of the Saccharomyces cerevisiae C-22 sterol desaturase gene, encoding a second cytochrome P-450 involved in ergosterol biosynthesis. Gene 1996; 169:105-9. [PMID: 8635732 DOI: 10.1016/0378-1119(95)00770-9] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The ERG5 gene from Saccharomyces cerevisiae was cloned by complementation of an erg5-1 mutation using a negative selection protocol involving screening for nystatin-sensitive transformants. ERG5 is the putative gene encoding the C-22 sterol desaturase required in ergosterol biosynthesis. The functional gene was localized to a 2.15-kb SacI-EcoRI DNA fragment containing an open reading frame of 538 amino acids (aa). ERG5 contains a 10-aa motif consistent with its role as a cytochrome P-450 (CyP450) enzyme and is similar to a number of mammalian CyP450 enzymes. Gene disruption demonstrates that ERG5 is not essential for cell viability.
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Affiliation(s)
- B A Skaggs
- Department of Biology, Indiana University-Purdue University at Indianapolis 46202, USA
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Kelly SL, Lamb DC, Corran AJ, Baldwin BC, Parks LW, Kelly DE. Purification and reconstitution of activity of Saccharomyces cerevisiae P450 61, a sterol delta 22-desaturase. FEBS Lett 1995; 377:217-20. [PMID: 8543054 DOI: 10.1016/0014-5793(95)01342-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
P450 was purified from microsomal fractions of a strain of Saccharomyces cerevisiae which contained detectable P450 despite the disruption of CYP51A1. The P450 had a molecular mass of 58 kDa, similar to P450 51A1, and in a reconstituted assay with rabbit NADPH-P450 reductase and dilauryl phosphotidylcholine exhibited activity for conversion of ergosta-5,7-dienol into ergosterol. N-Terminal amino acid sequencing of the purified protein corresponded to the translated sequence of P450 61 which was recently identified during sequencing of chromosome XIII. This allowed the function of this family of P450 to be identified as sterol delta 22-desaturation in the pathway of ergosterol biosynthesis.
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Affiliation(s)
- S L Kelly
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, Sheffield University, UK
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21
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Loubbardi A, Marcireau C, Karst F, Guilloton M. Sterol uptake induced by an impairment of pyridoxal phosphate synthesis in Saccharomyces cerevisiae: cloning and sequencing of the PDX3 gene encoding pyridoxine (pyridoxamine) phosphate oxidase. J Bacteriol 1995; 177:1817-23. [PMID: 7896706 PMCID: PMC176811 DOI: 10.1128/jb.177.7.1817-1823.1995] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Exogenous sterols do not permeate wild-type Saccharomyces cerevisiae in aerobic conditions. However, mutant strain FKerg7, affected in lanosterol synthase, is a sterol auxotroph which is able to grow aerobically in the presence of ergosterol. Viability of this strain depends on the presence of an additional mutation, aux30, that leads to sterol permeability. Cells bearing the aux30 mutation fail to grow in standard yeast nitrogen base medium containing pyridoxine but grow normally if pyridoxine is replaced by either pyridoxal or pyridoxamine. These mutants are characterized by a lack in pyridoxine (pyridoxamine) phosphate oxidase [P(N/M)P oxidase] (EC 1.4.3.5) activity. The pleiotropic phenotype induced by the aux30 mutation includes a strong perturbation in amino acid biosynthesis. Strains bearing the aux30 mutation also display atypic fatty acid, sterol, and cytochrome patterns. Transformation of an aux30 strain with a replicative vector carrying the wild-type PDX3 gene encoding P(N/M)P oxidase restored wild-type fatty acid, sterol, and cytochrome patterns and suppressed exogenous sterol accumulation. It is proposed that sterol permeation of aux30 strains in mainly the consequence of their leaky Hem- character. The amino acid sequence of S. cerevisiae P(N/M)P oxidase inferred from the nucleotide sequence of PDX3 shows a high percentage of homology with the corresponding enzymes from Escherichia coli and Myxococcus xanthus. Several putative Gcn4p binding sequences are present in the PDX3 promoter region, leading to the assumption that transcription of this gene is under the general control of nitrogen metabolism.
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Affiliation(s)
- A Loubbardi
- Laboratoire de Biochimie et Génétique des Microorganismes, Université de Poitiers, France
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Affiliation(s)
- E I Mercer
- Department of Biochemistry, University of Wales, Aberystwyth, Dyfed, U.K
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Lorenz RT, Parks LW. Involvement of heme components in sterol metabolism of Saccharomyces cerevisiae. Lipids 1991; 26:598-603. [PMID: 1779707 DOI: 10.1007/bf02536423] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
There is an intimate association between sterol biosynthesis in yeast and aerobicity. Besides the requirement for molecular oxygen for the epoxidation of squalene, cytochrome hemoproteins are involved in demethylation and desaturation steps. Regulatory effects of hemes on sterol formation have been demonstrated using specifically defective mutants of yeast. Heme competency participates in a mechanism whereby wild-type cells are prevented from taking exogenous sterols from the growth media. The multiple interactions of hemes and sterols appear to be associated with the variously defined functions for sterols in the yeast cells.
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Affiliation(s)
- R T Lorenz
- Department of Microbiology, North Carolina State University, Raleigh 27695-7615
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Abstract
Using yeast microsomes, 23-hydroxysterols were tested as intermediates in the formation of the sterol side delta 22-double bond. No evidence could be found supporting a two-stage mechanism of desaturation via hydroxylation and dehydration. Sterols with various side chains were tested as substrates. Those with alkyl substituents in the 24-alpha position were poor substrates. A series of sterols, including cyclopropyl sterols, were tested as mechanism-based inhibitors without success. Inhibition was observed with an isocyano-sterol.
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Affiliation(s)
- J L Giner
- Department of Chemistry, Stanford University, CA 94305
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Lorenz RT, Parks LW. Effects of lovastatin (mevinolin) on sterol levels and on activity of azoles in Saccharomyces cerevisiae. Antimicrob Agents Chemother 1990; 34:1660-5. [PMID: 2285278 PMCID: PMC171901 DOI: 10.1128/aac.34.9.1660] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The hypocholesterolemic drug lovastatin (mevinolin) was found to be very effective in lowering the sterol levels of the wild-type yeast Saccharomyces cerevisiae. Lovastatin dramatically decreased the steryl ester content from 2.62 to 0.8 micrograms/mg (dry weight), whereas the free sterol content decreased only from 2.79 to 2.24 micrograms/mg (dry weight) when lovastatin was present in the medium at 10 micrograms/ml. At higher concentrations (100 micrograms/ml), lovastatin nearly abolished the accumulation of steryl esters and decreased the free sterol concentration to less than 1.3 micrograms/mg (dry weight). As a result of the lowered sterol levels, proportional amounts of exogenous sterol were taken up from the medium during aerobic, respiratory conditions. Nearly all of the exogenous sterol taken up was partitioned into the free sterol fraction. The inhibition of sterol esterification in the presence of lovastatin was dependent on heme synthesis. The result of these combined effects caused the MICs of three azole antifungal drugs (ketoconazole, clotrimazole, and miconazole) to be lowered from 6- to 32-fold when lovastatin was present in the medium at 10 micrograms/ml.
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Affiliation(s)
- R T Lorenz
- Department of Microbiology, North Carolina State University, Raleigh 27695-7615
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Inhibitors of ergosterol biosynthesis and growth of the trypanosomatid protozoan Crithidia fasciculata. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)34073-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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27
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Positive and negative transcriptional control by heme of genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase in Saccharomyces cerevisiae. Mol Cell Biol 1990. [PMID: 2685574 DOI: 10.1128/mcb.9.12.5702] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Responses of the yeast genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase, HMG1 and HMG2, to in vivo changes in heme concentrations were investigated. Expression of the genes was determined by direct measurement of the mRNA transcribed from each gene, by direct assay of the enzyme activity encoded by each gene, and by measurement of the expression of lacZ fusions to the control regions of each gene. These studies indicated that expression of HMG1 was stimulated by heme, whereas expression of HMG2 was repressed by heme. The effect of heme on HMG1 expression was mediated by the HAP1 transcriptional regulator and was independent of HAP2. Thus, the genes encoding the 3-hydroxy-3-methylglutaryl coenzyme A reductase isozymes join a growing list of gene pairs that are regulated by heme in opposite ways.
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Thorsness M, Schafer W, D'Ari L, Rine J. Positive and negative transcriptional control by heme of genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase in Saccharomyces cerevisiae. Mol Cell Biol 1989; 9:5702-12. [PMID: 2685574 PMCID: PMC363742 DOI: 10.1128/mcb.9.12.5702-5712.1989] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Responses of the yeast genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase, HMG1 and HMG2, to in vivo changes in heme concentrations were investigated. Expression of the genes was determined by direct measurement of the mRNA transcribed from each gene, by direct assay of the enzyme activity encoded by each gene, and by measurement of the expression of lacZ fusions to the control regions of each gene. These studies indicated that expression of HMG1 was stimulated by heme, whereas expression of HMG2 was repressed by heme. The effect of heme on HMG1 expression was mediated by the HAP1 transcriptional regulator and was independent of HAP2. Thus, the genes encoding the 3-hydroxy-3-methylglutaryl coenzyme A reductase isozymes join a growing list of gene pairs that are regulated by heme in opposite ways.
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Affiliation(s)
- M Thorsness
- Department of Biochemistry, University of California, Berkeley 94720
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Abstract
The leaky heme mutants G204, G216, and G214 are shown to accumulate exogenous sterols. Unlike hem mutants which have complete blocks in the heme pathway, these strains do not require ergosterol, methionine, or unsaturated fatty acids for growth. The addition of aminolevulinic acid to the growth medium inhibited sterol uptake in G204 96% but had only a slight effect on sterol uptake by strains G214 and G216. Sterol uptake in all three strains was inhibited 83-94% when cells were grown in the presence of hematin. Sterol analysis of these strains grown in the presence and absence of either aminolevulinic acid or hematin revealed that saturation of the cell membrane with ergosterol was not responsible for the dramatic decrease in sterol uptake. These results suggest that sterol uptake by yeast cells is controlled by heme, and explain the non-viability of yeast strains that are heme competent and auxotrophic for sterols.
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Affiliation(s)
- D L Shinabarger
- Department of Microbiology, North Carolina State University, Raleigh 27695-7615
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Gealt MA, Abdollahi A, Evans JL. Lipids and lipoidal mycotoxins of fungi. CURRENT TOPICS IN MEDICAL MYCOLOGY 1989; 3:218-47. [PMID: 2688917 DOI: 10.1007/978-1-4612-3624-5_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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31
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Nes WR, Dhanuka IC. Inhibition of sterol synthesis by delta 5-sterols in a sterol auxotroph of yeast defective in oxidosqualene cyclase and cytochrome P-450. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)37863-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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32
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Yoshida Y. Cytochrome P450 of fungi: primary target for azole antifungal agents. CURRENT TOPICS IN MEDICAL MYCOLOGY 1988; 2:388-418. [PMID: 3288361 DOI: 10.1007/978-1-4612-3730-3_11] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Cytochromes of fungi are essentially similar to those of animals. Cytochromes of fungi constitute two electron transport systems occurring in mitochondria and the endoplasmic reticulum. The former system, called the respiratory chain, contributes to cellular respiration and ATP generation, whereas the later system, named the microsomal electron transport system, is responsible for biosynthesis of several cellular components. The oxidative metabolism of lanosterol, that is included in the biosynthetic pathway of ergosterol, is one of the important functions of the microsomal electron transport system, which is catalyzed by P450(14DM). Many azole antifungal agents avidly combine with P450(14DM) and inhibit the oxidative removal of C-32 (the 14 alpha-demethylation) of lanosterol. This inhibition causes depletion of ergosterol and accumulation of 14-methylsterols in the membrane of fungal cells. Such change in sterol composition disturbs membrane function and results in growth inhibition and death of the fungal cells. Accordingly, P450(14DM) is considered as the primary target for azole antifungal agents. Cytochrome P450, which mediates the 14 alpha-demethylation of lanosterol, is also present in mammalian cells. Mammalian cells contain various species of cytochrome P450 which are responsible for many important cellular metabolic functions. If azole antifungal agents inhibit mammalian cytochrome P450 too, their systemic use may result in potentially significant adverse reactions. The high selectivity of azole antifungal agents for fungal P450(14DM) will be necessary for their systemic application. Binding ability of an azole antifungal agent to P450(14DM) is predominantly determined by the substituent at N-1 of the azole group, and the substituent must interact with the substrate site of the cytochrome. Extensive modification of the N-1 substituents and the screening of newly developed compounds with respect to the selectivity to fungal P450(14DM) with some conventional methods will be necessary. For this project, a biochemical understanding of cytochrome P450 and other cytochromes is important.
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Lorenz RT, Parks LW. Regulation of ergosterol biosynthesis and sterol uptake in a sterol-auxotrophic yeast. J Bacteriol 1987; 169:3707-11. [PMID: 3301810 PMCID: PMC212455 DOI: 10.1128/jb.169.8.3707-3711.1987] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Inhibition of sterol uptake in Saccharomyces cerevisiae sterol auxotroph FY3 (alpha hem1 erg7 ura) by delta-aminolevulinic acid (ALA) is dependent on the ability of the organism to synthesize heme from ALA. Sterol-depleted cells not exposed to ALA or strain PFY3 cells, with a double heme mutation, exposed to ALA did not exhibit inhibition of sterol uptake. Addition of ALA to sterol-depleted FY3 stimulated production of a high endogenous concentration of 2,3-oxidosqualene (25.55 micrograms mg-1 [dry weight]) at 24 h, whereas FY3 not exposed to ALA or PFY3 exposed to ALA did not accumulate 2,3-oxidosqualene. The high concentration of 2,3-oxidosqualene in FY3 with ALA decreased, and 2,3;22,23-dioxidosqualene increased to a very high level. The elevation of 2,3-oxidosqualene by ALA was correlated with a fivefold increase in the activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (EC 1.1.1.34). The enhanced activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase was prevented by cycloheximide but not chloramphenicol and was dependent on a fermentative energy source. Inhibition of sterol uptake could not be attributed to 2,3-oxidosqualene or 2,3;22,23-dioxidosqualene but was due to a nonsaturating level of ergosterol produced as a consequence of heme competency through a leaky erg7 mutation.
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Lorenz RT, Rodriguez RJ, Lewis TA, Parks LW. Characteristics of sterol uptake in Saccharomyces cerevisiae. J Bacteriol 1986; 167:981-5. [PMID: 3528131 PMCID: PMC215968 DOI: 10.1128/jb.167.3.981-985.1986] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
A Saccharomyces cerevisiae sterol auxotroph, FY3 (alpha hem1 erg7 ura), was used to probe the characteristics of sterol uptake in S. cerevisiae. The steady-state cellular concentration of free sterol at the late exponential phase of growth could be adjusted within a 10-fold range by varying the concentration of exogenously supplied sterol. When cultured on 1 microgram of sterol ml-1, the cells contained a minimal cellular free-cholesterol concentration of 0.85 nmol/mg (dry weight) and were termed sterol depleted. When cultured on 11 micrograms of sterol ml-1 or more, the cells contained a maximal cellular free-cholesterol concentration of 6.8 nmol/mg (dry weight) and were termed free sterol saturated. Cells with free-sterol concentrations below the maximal level were capable of accumulating free sterol from the medium. The capacity of the cells for cholesterol uptake was inversely proportional to the initial intracellular concentration. The uptake of sterol was shown to be a nonactive process that is independent of cellular energy sources or viability. The intracellular transport of sterol for esterification is not sensitive to anti-microtubule agents.
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Sterol Biosynthesis in Fungi, a Target for Broad Spectrum Fungicides. CHEMISTRY OF PLANT PROTECTION 1986. [DOI: 10.1007/978-3-642-69790-6_1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Vanden Bossche H. Biochemical targets for antifungal azole derivatives: hypothesis on the mode of action. CURRENT TOPICS IN MEDICAL MYCOLOGY 1985; 1:313-51. [PMID: 3916772 DOI: 10.1007/978-1-4613-9547-8_12] [Citation(s) in RCA: 223] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The selective interaction of low concentrations of azole derivatives and other nitrogen heterocycles with cytochrome P-450 may be at the origin of the inhibition of ergosterol biosynthesis. From the depletion of ergosterol and the concomitant accumulation of 14 alpha-methylsterols, alterations in membrane functions, the synthesis and activity of membrane-bound enzymes, mitochondrial activities, and an uncoordinated activation of chitin synthase may result. Since chitin synthesis is more important in the hyphal form than in the budding form of C. albicans, the uncoordinated activation of chitin synthesis may be more trouble for the hyphal growth than for yeast budding. The assumption is made that from this difference the greater sensitivity of hyphal growth to azole antifungal agents may originate. It is also assumed that the higher degree of lipid unsaturation may be related to an inhibition of ergosterol biosynthesis. The inhibition of fatty acid desaturation and elongation induced by higher doses of miconazole and ketoconazole and the longer contact times might be related to interference with membrane fluidity, or it might due to chelation of the iron used in the oxidation reduction sequence during desaturation. The decreased availability of ergosterol and the accumulation of 14 alpha-methylsterols also may provide the environment needed to inactivate membrane-bound enzymes; e.g., cytochrome c peroxidase. However, it is still too speculative to correlate effects on membrane components with miconazole-induced changes in properties of all oxidases; e.g., the NADH-dependent, cyanide-insensitive oxidase. The accumulation of toxic concentrations of hydrogen peroxide, resulting from an increased NADH-oxidase activity and disappearance of the peroxidase and catalase activity, may contribute to the degeneration of subcellular structures. The complete disappearance of catalase observed at concentrations of miconazole greater than or equal to 10(-5) M may originate from direct effects on the cell. At these high concentrations reached only by topical application, direct membrane damage resulting from interaction of miconazole with lipids was observed. These direct interactions result in an inhibition of membrane-bound enzyme and mitochondrial activities and in leakage of intracellular components. The direct interactions were much less pronounced in cells treated with ketoconazole. This correlates with the smaller area occupied in the membrane per ketoconazole molecule (30 A2), compared with that occupied in the membrane per miconazole molecule (90 A2).(ABSTRACT TRUNCATED AT 400 WORDS)
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Kamihara T, Nakamura I. Regulation of respiration and its related metabolism by vitamin B1 and vitamin B6 in Saccharomyces yeasts. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 1984; 29:35-82. [PMID: 6437158 DOI: 10.1007/bfb0000690] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Hata S, Nishino T, Katsuki H, Aoyama Y, Yoshida Y. Two species of cytochrome P-450 involved in ergosterol biosynthesis of yeast. Biochem Biophys Res Commun 1983; 116:162-6. [PMID: 6357195 DOI: 10.1016/0006-291x(83)90395-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Discrimination of cytochrome P-450 involved in delta 22-desaturation of ergosta-5,7-dien-3 beta-o1 (P-450(22)-DS) from that involved in lanosterol 14 alpha-demethylation (P-450(14)-DM) in ergosterol biosynthesis was investigated with microsomes of several strains of Saccharomyces cerevisiae. In mutant N22 which is partially defective in the delta 22-desaturation, the 14 alpha-demethylation was not blocked. In contrast, mutant SG1 which is known to lack the 14 alpha-demethylation showed a significant activity of the delta 22-desaturation. The delta 22-desaturation activity was markedly increased upon aerobic adaptation of yeast cells but the 14 alpha-demethylation was not affected. Buthiobate, a specific inhibitor of P-450(14)-DM, and rabbit antibodies against P-450(14)-DM did not inhibit the delta 22-desaturation activity at all. It is evident from the obtained observations that these phenomena are not explainable in terms of NADPH-cytochrome P-450 reductase. These results indicate that P-450(22)-DS is different from P-450(14)-DM in molecular species.
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Aoyama Y, Yoshida Y, Hata S, Nishino T, Katsuki H. Buthiobate: a potent inhibitor for yeast cytochrome P-450 catalyzing 14 alpha-demethylation of lanosterol. Biochem Biophys Res Commun 1983; 115:642-7. [PMID: 6414474 DOI: 10.1016/s0006-291x(83)80192-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Buthiobate (S-n-butyl S'-p-tert-butylbenzyl N-3-pyridyldithiocarbon-imidate), a fungicide, inhibited 14 alpha-demethylation of lanosterol catalyzed by a reconstituted enzyme system consisting of cytochrome P-450 (P-450(14)-DM) and NADPH-cytochrome P-450 reductase both purified from Saccharomyces cerevisiae. Concentration of buthiobate necessary for the 50% inhibition was 0.3 microM and this value was markedly lower than those of metyrapone and SKF-525A. Buthiobate bound stoichiometrically to P-450(14)-DM and induced Type II spectral change of the cytochrome. Buthiobate inhibited lanosterol-dependent enzymatic reduction of the cytochrome. These facts indicate that buthiobate binds to P-450(14)-DM with high affinity and acts as a potent inhibitor on the cytochrome.
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Rodriguez RJ, Parks LW. Structural and physiological features of sterols necessary to satisfy bulk membrane and sparking requirements in yeast sterol auxotrophs. Arch Biochem Biophys 1983; 225:861-71. [PMID: 6354097 DOI: 10.1016/0003-9861(83)90099-1] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A variety of sterols and stanols have been analyzed for their ability to satisfy bulk membrane and high-specificity (sparking) functions in three yeast sterol auxotrophs. While many sterols and stanols satisfied bulk membrane requirements, only those possessing a C-5,6 unsaturation or capable of being desaturated at C-5 fulfilled the high-specificity sparking requirement. Unsaturation of the A-ring or beta-saturation of a C-5,6 double bond rendered both sterol and stanol unsuitable for either function. The C-28 methyl group of ergosterol, while not required for growth, allowed for greater ease of desaturation at C-5 in vivo. As a result some sterols and stanols lacking the C-28 methyl were incapable of satisfying the sparking requirement while identical compounds possessing the C-28 methyl were able to fulfill the sparking function(s). These data are extended to hypothesize a role for the C-28 methyl group of ergosterol in yeast.
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Jahnke L, Klein HP. Oxygen requirements for formation and activity of the squalene epoxidase in Saccharomyces cerevisiae. J Bacteriol 1983; 155:488-92. [PMID: 6348021 PMCID: PMC217714 DOI: 10.1128/jb.155.2.488-492.1983] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The effect of oxygen on squalene epoxidase activity in Saccharomyces cerevisiae was investigated. In cells grown in standing cultures, the epoxidase was localized mainly in the "mitochondrial" fraction. Upon aeration, enzyme activity increased and the newly formed enzyme was associated with the "microsomal" fraction. At 0.03% (vol/vol) oxygen, epoxidase levels doubled, whereas the ergosterol level was only slightly increased. Cycloheximide inhibited the increase in epoxidase under these conditions. An apparent Km for oxygen of 0.38% (vol/vol) was determined from a crude particulate preparation for the epoxidase.
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Aoyama Y, Yoshida Y, Hata S, Nishino T, Katsuki H, Maitra US, Mohan VP, Sprinson DB. Altered cytochrome P-450 in a yeast mutant blocked in demethylating C-32 of lanosterol. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)44627-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Hata S, Nishino T, Oda Y, Katsuki H, Aoyama Y, Yoshida Y. Isolation of ergosta-5,7-diene-3β,23ξ-diol from yeast. Tetrahedron Lett 1983. [DOI: 10.1016/s0040-4039(00)86240-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Hata S, Nishino T, Ariga N, Katsuki H. Effect of detergents on sterol synthesis in a cell-free system of yeast. J Lipid Res 1982. [DOI: 10.1016/s0022-2275(20)38082-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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