C-5 sterol desaturase

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C-5 sterol desaturase (also known as sterol C-5 desaturase and C5SD) is an enzyme that is highly conserved among eukaryotes and catalyzes the dehydrogenation of a C-5(6) bond in a sterol intermediate compound as a step in the biosynthesis of major sterols. The precise structure of the enzyme's substrate varies by species. For example, the human C-5 sterol desaturase (also known as lathosterol oxidase) oxidizes lathosterol, while its ortholog ERG3 in the yeast Saccharomyces cerevisiae oxidizes episterol. [1] [2]

Contents

The precise structural details of C-5 sterol desaturase substrates vary across eukaryotes. Shown below the reaction scheme are three possible distal groups along with biosynthetic pathways and species they are found in. C5DS reactions.tif
The precise structural details of C-5 sterol desaturase substrates vary across eukaryotes. Shown below the reaction scheme are three possible distal groups along with biosynthetic pathways and species they are found in.

Mechanism

C-5 sterol desaturase couples sterol oxidation to the oxidation of NAD(P)H and the reduction of molecular oxygen. [2] Either NADH or NADPH can be used; in the model plant species Arabidopsis thaliana C-5 sterol desaturase catalyzes the reaction twice as fast with NADH while in S. cerevisiae the enzyme has little preference. [1] [4] The precise details of the reaction have been thought to vary between mammals and yeast. [1] However, the enzymes do share a conserved cluster of histidine residues, which when mutated (in A. thaliana) dramatically reduce or eliminate enzyme activity, suggesting the involvement of a coordinated iron cation in the mechanism. [4] Mutagenesis studies suggest that in A. thaliana threonine 114 (which is a serine in humans, mice, and yeast) may help to stabilize the enzyme-substrate complex. [4] Rahier has proposed a reaction mechanism in which an iron-coordinated oxygen abstracts a hydrogen from the substrate leading to a radical intermediate. [5]

Biological role

C-5 sterol desaturase catalyzes an intermediate step in the synthesis of major sterols. The particular biosynthetic pathway varies across eukaryotes. In animals C5SD catalyzes the dehydration of lathosterol to 7-dehydrocholesterol, a step in the synthesis of cholesterol. [6] Cholesterol serves multiple roles in the cell including modulating membrane fluidity serving as a precursor to steroid hormones. [6] In fungi C5SD catalyzes the dehydration of episterol as a step in the synthesis of ergosterol, a sterol that regulates cell membrane fluidity and permeability. [1] [7] In plants such as Arabidopsis thaliana, C-5 sterol desaturase catalyzes the dehydrogenation of episterol and avenasterol in a pathway thought to lead to a variety of membrane components as well as a class of hormones called brassinosteroids. [8]

Subcellular localization

Based on its amino acid profile C-5 sterol desaturase appears to have four to five membrane-spanning regions, suggesting that it is a transmembrane protein. [9] C5SD activity has been demonstrated in microsomes from rat tissue, implying that rat enzyme localizes to the endoplasmic reticulum [10] [11] Fluorescence microscopy experiments have shown that in the ciliate Tetrahymena thermophila C5SD localizes to the endoplasmic reticulum and that in S. cerevisiae C5SD localizes to both the endoplasmic reticulum and vesicles. [12] [13] In Arabidopsis thaliana C5SD is located in both the endoplasmic reticulum and lipid particles. [14]

Clinical Relevance

Antifungal resistance

The common class of antifungal drugs known as azoles disrupts the fungal sterol biosynthesis pathway, upstream of C-5 sterol desaturase leading to the accumulation of nontoxic 14α-methylated sterols. C5SD then converts these intermediates into a toxic product. Consequently, in both the pathogenic fungus Candida albicans and model organism S. cerevisiae mutations in the gene encoding C-5 sterol desaturase (ERG3) allow the cell to avoid synthesizing the toxic sterol products and have been shown to confer azole resistance. [15] [16] In at least the case of fluconazole, antifungal resistance due to C5SD inactivation is dependent on the activity of the chaperone protein Hsp90 and the phosphatase calcineurin. [17] [18] However, the clinical relevance of this azole resistance mechanism is controversial because while the deletion of ERG3 alone confers fluconazole resistance to C. albicans in vitro, it is insufficient to confer fluconazole resistance in a live mouse model. [19]

Lathosterolosis

In at least one patient, a deficiency in C-5 sterol desaturase activity (termed lathosterolosis) was associated with multiple malformations, metal retardation, and liver disease. [9] This patient was also found to have low levels of blood cholesterol and high levels of lathosterol in cell membranes when compared to those of healthy control subjects. These symptoms resemble those of other defects in cholesterol synthesis such as Smith–Lemli–Opitz syndrome. [9] [20]

Potential applications

Scientists have found that tomato plants engineered with the C-5 sterol desaturase from the mushroom Flammulina velutipes show improved drought tolerance and fungal pathogen resistance as well as increased iron and polyunsaturated fat content. [21] The authors of the study suggest that the fungal enzyme may be a useful tool for plant biotechnology as improving multiple aspects of a crop is typically time- and labor-intensive.

Related Research Articles

<span class="mw-page-title-main">Steroid</span> Any organic compound having sterane as a core structure

A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and as signaling molecules. Hundreds of steroids are found in plants, animals and fungi. All steroids are manufactured in cells from the sterols lanosterol (opisthokonts) or cycloartenol (plants). Lanosterol and cycloartenol are derived from the cyclization of the triterpene squalene.

<span class="mw-page-title-main">Antifungal</span> Pharmaceutical fungicide or fungistatic used to treat and prevent mycosis

An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as cryptococcal meningitis, and others. Such drugs are usually obtained by a doctor's prescription, but a few are available over the counter (OTC). The evolution of antifungal resistance is a growing threat to health globally.

<span class="mw-page-title-main">Ergosterol</span> Chemical compound

Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many fungi and protozoa cannot survive without ergosterol, the enzymes that synthesize it have become important targets for drug discovery. In human nutrition, ergosterol is a provitamin form of vitamin D2; exposure to ultraviolet (UV) light causes a chemical reaction that produces vitamin D2.

<span class="mw-page-title-main">Farnesyl-diphosphate farnesyltransferase</span> Class of enzymes

Squalene synthase (SQS) or farnesyl-diphosphate:farnesyl-diphosphate farnesyl transferase is an enzyme localized to the membrane of the endoplasmic reticulum. SQS participates in the isoprenoid biosynthetic pathway, catalyzing a two-step reaction in which two identical molecules of farnesyl pyrophosphate (FPP) are converted into squalene, with the consumption of NADPH. Catalysis by SQS is the first committed step in sterol synthesis, since the squalene produced is converted exclusively into various sterols, such as cholesterol, via a complex, multi-step pathway. SQS belongs to squalene/phytoene synthase family of proteins.

<span class="mw-page-title-main">Lanosterol synthase</span> Mammalian protein found in Homo sapiens

Lanosterol synthase is an oxidosqualene cyclase (OSC) enzyme that converts (S)-2,3-oxidosqualene to a protosterol cation and finally to lanosterol. Lanosterol is a key four-ringed intermediate in cholesterol biosynthesis. In humans, lanosterol synthase is encoded by the LSS gene.

<span class="mw-page-title-main">Isopentenyl-diphosphate delta isomerase</span> Class of enzymes

Isopentenyl pyrophosphate isomerase, also known as Isopentenyl-diphosphate delta isomerase, is an isomerase that catalyzes the conversion of the relatively un-reactive isopentenyl pyrophosphate (IPP) to the more-reactive electrophile dimethylallyl pyrophosphate (DMAPP). This isomerization is a key step in the biosynthesis of isoprenoids through the mevalonate pathway and the MEP pathway.

In enzymology, a sterol 24-C-methyltransferase is an enzyme that catalyzes the chemical reaction

In enzymology, a Delta24(241)-sterol reductase (EC 1.3.1.71) is an enzyme that catalyzes the chemical reaction

In enzymology, a Δ7-sterol 5(6)-desaturase is an enzyme that catalyzes the chemical reaction

<span class="mw-page-title-main">Sterol 14-demethylase</span> Class of enzymes

In enzymology, a sterol 14-demethylase (EC 1.14.13.70) is an enzyme of the Cytochrome P450 (CYP) superfamily. It is any member of the CYP51 family. It catalyzes a chemical reaction such as:

Sterol O-acyltransferase is an intracellular protein located in the endoplasmic reticulum that forms cholesteryl esters from cholesterol.

<span class="mw-page-title-main">Oxysterol-binding protein</span>

The oxysterol-binding protein (OSBP)-related proteins (ORPs) are a family of lipid transfer proteins (LTPs). Concretely, they constitute a family of sterol and phosphoinositide binding and transfer proteins in eukaryotes that are conserved from yeast to humans. They are lipid-binding proteins implicated in many cellular processes related with oxysterol, including signaling, vesicular trafficking, lipid metabolism, and nonvesicular sterol transport.

<span class="mw-page-title-main">Sterol-C5-desaturase-like</span> Protein-coding gene in the species Homo sapiens

Lathosterol oxidase is a Δ7-sterol 5(6)-desaturase enzyme that in humans is encoded by the SC5D gene.

Membrane contact sites (MCS) are close appositions between two organelles. Ultrastructural studies typically reveal an intermembrane distance in the order of the size of a single protein, as small as 10 nm or wider, with no clear upper limit. These zones of apposition are highly conserved in evolution. These sites are thought to be important to facilitate signalling, and they promote the passage of small molecules, including ions, lipids and reactive oxygen species. MCS are important in the function of the endoplasmic reticulum (ER), since this is the major site of lipid synthesis within cells. The ER makes close contact with many organelles, including mitochondria, Golgi, endosomes, lysosomes, peroxisomes, chloroplasts and the plasma membrane. Both mitochondria and sorting endosomes undergo major rearrangements leading to fission where they contact the ER. Sites of close apposition can also form between most of these organelles most pairwise combinations. First mentions of these contact sites can be found in papers published in the late 1950s mainly visualized using electron microscopy (EM) techniques. Copeland and Dalton described them as “highly specialized tubular form of endoplasmic reticulum in association with the mitochondria and apparently in turn, with the vascular border of the cell”.

Ditrans,polycis-polyprenyl diphosphate synthase is an enzyme with systematic name (2E,6E)-farnesyl-diphosphate:isopentenyl-diphosphate cistransferase . This enzyme catalyses the following chemical reaction

Pierre Benveniste, born on 22 December 1937 in Neuilly-sur-Seine, is a French researcher in plant biochemistry and professor at the University of Strasbourg.

ERG11 or Sterol 14-demethylase is a fungal cytochrome P450 enzyme originally from Saccharomyces cerevisiae, belongs to family CYP51, with the CYP Symbol CYP51F1. ERG11 catalyzes the C14-demethylation of lanosterol to 4,4'-dimethyl cholesta-8,14,24-triene-3-beta-ol which is the first step of biosynthesis of the zymosterol, zymosterol will be further converted into Ergosterol.

<span class="mw-page-title-main">ERG3</span>

ERG3 or sterol C-5 desaturase is a fungal enzyme originally from Saccharomyces cerevisiae, the human ortholog of ERG3 is SC5D. ERG3 localizes to both the endoplasmic reticulum and vesicles, catalyzes the C5(6)-dehydrogenation of episterol to 5-dehydroepisterol, 5-Dehydroepisterol will be further converted into ergosterol.

ERG5 or Sterol 22-desaturase is a cytochrome P450 enzyme in the ergosterol biosynthesis pathway of fungi Saccharomyces cerevisiae, with the CYP Symbol CYP61A1. CYP61A1 is one of only three P450 enzyme found in baker's yeast, the other two are CYP51F1 and CYP56A1. The ortholog in Schizosaccharomyces pombe, was named CYP61A3 for historical reasons, and is only one of two P450 enzyme found with CYP51F1. ERG5 catalyzes the C22-C23 double bond formation on the sterol side chain of ergostatrienol to convert it into ergostatetraenol, then the C24 double bond of ergostatetrenol will be hydrogenation reduced into ergosterol by ERG4.

ERG4 or Delta(24 )-sterol reductase or Delta(24 )-sterol reductase is an enzyme that catalyzes the last step of ergosterol biosynthesis pathway in fungi Saccharomyces cerevisiae, which 5,7,22,24(28)-ergostatetraenol converted into ergosterol.

References

  1. 1 2 3 4 5 Osumi Takashi; Nishino Tokuzo; Katsuki Hirohiko (1979). "Studies on the delta 5-desaturation in ergosterol biosynthesis in yeast". The Journal of Biochemistry. 85 (3): 819–826. PMID   34600.
  2. 1 2 3 Kawata S, Trzaskos JM, Gaylor JL (1985). "Microsomal enzymes of cholesterol biosynthesis from lanosterol. Purification and characterization of delta 7-sterol 5-desaturase of rat liver microsomes". Journal of Biological Chemistry. 260 (11): 6609–6617. doi: 10.1016/S0021-9258(18)88825-1 . PMID   3997841.
  3. ↑ Choe Sunghwa; Noguchi Takahiro; Fujioka Shozo; Takatsuto Suguru; Tissier Christophe P; Gregory Brian D; Ross Amanda S; Tanaka Atsushi; Yoshida Shigeo; Tax Frans E; et al. (1999). "The Arabidopsis dwf7/ste1 mutant is defective in the delta 7 sterol C-5 desaturation step leading to brassinosteroid biosynthesis". The Plant Cell. 11 (2): 207–221. doi:10.1105/tpc.11.2.207. PMC   144158 . PMID   9927639.
  4. 1 2 3 Taton Maryse; Husselstein Tania; Benveniste Pierre; Rahier Alain (2000). "Role of highly conserved residues in the reaction catalyzed by recombinant delta 7-sterol-C5 (6)-desaturase studied by site-directed mutagenesis". Biochemistry. 39 (4): 701–711. doi:10.1021/bi991467t. PMID   10651635.
  5. ↑ Rahier Alain (2001). "Deuterated delta 7-cholestenol analogues as mechanistic probes for wild-type and mutated delta 7-sterol-C5 (6)-desaturase". Biochemistry. 40 (1): 256–267. doi:10.1021/bi001696b. PMID   11141078.
  6. 1 2 Risley John M (2002). "Cholesterol biosynthesis: Lanosterol to cholesterol". Journal of Chemical Education. 79 (3): 377. doi:10.1021/ed079p377.
  7. ↑ Abe Fumiyoshi; Hiraki Toshiki (2009). "Mechanistic role of ergosterol in membrane rigidity and cycloheximide resistance in Saccharomyces cerevisiae". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1788 (3): 743–752. doi: 10.1016/j.bbamem.2008.12.002 . PMID   19118519.
  8. ↑ Hartmann Marie-Andrée (1998). "Plant sterols and the membrane environment". Trends in Plant Science. 3 (5): 170–175. doi:10.1016/S1360-1385(98)01233-3.
  9. 1 2 3 Brunetti-Pierri Nicola; Corso Gaetano; Rossi Massimiliano; Ferrari Paola; Balli Fiorella; Rivasi Francesco; Annunziata Ida; Ballabio Andrea; Russo Antonio Dello; Andria Generoso; et al. (2002). "Lathosterolosis, a novel multiple-malformation/mental retardation syndrome due to deficiency of beta-hydroxysteroid-delta 5-desaturase". The American Journal of Human Genetics. 71 (4): 952–958. doi:10.1086/342668. PMC   378549 . PMID   12189593.
  10. ↑ Grinstead GF, Gaylor JL (1982). "Total enzymic synthesis of cholesterol from 4, 4, 14 alpha-trimethyl-5 alpha-cholesta-8, 24-dien-3 beta-ol. Solubilization, resolution, and reconstitution of delta 7-sterol 5-desaturase". The Journal of Biological Chemistry. 257 (23): 13937–44. doi: 10.1016/S0021-9258(19)45323-4 . PMID   6815183.
  11. ↑ Ishibashi Teruo (2002). "Supernatant protein relevant to the activity of membrane-bound enzymes: studies on lathosterol 5-desaturase". Biochemical and Biophysical Research Communications. 292 (5): 1293–1298. doi:10.1006/bbrc.2002.2012. PMID   11969231.
  12. ↑ Natter Klaus; Leitner Peter; Faschinger Alexander; Wolinski Heimo; McCraith Stephen; Fields Stanley; Kohlwein Sepp D (2005). "The spatial organization of lipid synthesis in the yeast Saccharomyces cerevisiae derived from large scale green fluorescent protein tagging and high resolution microscopy". Molecular & Cellular Proteomics. 4 (5): 662–672. doi: 10.1074/mcp.M400123-MCP200 . PMID   15716577.
  13. ↑ Poklepovich Tomas J, Rinaldi Mauro A, Tomazic Mariela L, Favale Nicolas O, Turkewitz Aaron P, Nudel Clara B, Nusblat Alejandro D (2012). "The cytochrome b 5 dependent C-5 (6) sterol desaturase DES5A from the endoplasmic reticulum of Tetrahymena thermophila complements ergosterol biosynthesis mutants in Saccharomyces cerevisiae". Steroids. 77 (13): 1313–1320. doi:10.1016/j.steroids.2012.08.015. PMC   3501532 . PMID   22982564.
  14. ↑ Silvestro Daniele; Andersen Tonni Grube; Schaller Hubert; Jensen Poul Erik (2013). "Plant sterol metabolism. Delta 7-Sterol-C5-desaturase (STE1/DWARF7), Delta 5, 7-sterol-Delta 7-reductase (DWARF5) and Delta 24-sterol-Delta 24-reductase (DIMINUTO/DWARF1) show multiple subcellular localizations in Arabidopsis thaliana (Heynh) L". PLOS ONE. 8 (2): e56429. doi: 10.1371/journal.pone.0056429 . PMC   3568079 . PMID   23409184.
  15. ↑ Jackson Colin J, Lamb David C, Manning Nigel J, Kelly Diane E, Kelly Steven L (2003). "Mutations in Saccharomyces cerevisiae sterol C5-desaturase conferring resistance to the CYP51 inhibitor fluconazole". Biochemical and Biophysical Research Communications. 309 (4): 999–1004. doi:10.1016/j.bbrc.2003.08.098. PMID   13679073.
  16. ↑ Vale-Silva LA, Coste AT, Ischer F, Parker JE, Kelly SL, Pinto E, Sanglard D (2012). "Azole resistance by loss of function of the sterol delta 5, 6-desaturase gene (ERG3) in Candida albicans does not necessarily decrease virulence". Antimicrobial Agents and Chemotherapy. 56 (4): 1960–1968. doi:10.1128/AAC.05720-11. PMC   3318373 . PMID   22252807.
  17. ↑ Cowen, Leah E; Lindquist, Susan (2005). "Hsp90 potentiates the rapid evolution of new traits: drug resistance in diverse fungi". Science. 309 (5744): 2185–2189. doi:10.1126/science.1118370. PMID   16195452. S2CID   52847795.
  18. ↑ Cowen, Leah E; Carpenter, Anne E; Matangkasombut, Oranart; Fink, Gerald R; Lindquist, Susan (2006). "Genetic architecture of Hsp90-dependent drug resistance". Eukaryotic Cell. 5 (12): 2184–2188. doi:10.1128/EC.00274-06. PMC   1694807 . PMID   17056742.
  19. ↑ Miyazaki Taiga; Miyazaki Yoshitsugu; Izumikawa Koichi; Kakeya Hiroshi; Miyakoshi Shunichi; Bennett John E; Kohno Shigeru (2006). "Fluconazole treatment is effective against a Candida albicans erg3/erg3 mutant in vivo despite in vitro resistance". Antimicrobial Agents and Chemotherapy. 50 (2): 580–586. doi:10.1128/AAC.50.2.580-586.2006. PMC   1366932 . PMID   16436713.
  20. ↑ Krakowiak Patrycja A; Wassif Christopher A; Kratz Lisa; Cozma Diana; Kovarova Martina; Harris Ginny; Grinberg Alexander; Yang Yinzi; Hunter Alasdair GW; Tsokos Maria; et al. (2003). "Lathosterolosis: an inborn error of human and murine cholesterol synthesis due to lathosterol 5-desaturase deficiency". Human Molecular Genetics. 12 (13): 1631–1641. doi: 10.1093/hmg/ddg172 . PMID   12812989.
  21. ↑ Kamthan Ayushi; Kamthan Mohan; Azam Mohammad; Chakraborty Niranjan; Chakraborty Subhra; Datta Asis (2012). "Expression of a fungal sterol desaturase improves tomato drought tolerance, pathogen resistance and nutritional quality". Scientific Reports. 2: 951. doi:10.1038/srep00951. PMC   3517979 . PMID   23230516.
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