Sterol 14-demethylase

In enzymology, a sterol 14-demethylase (EC 1.14.13.70) is an enzyme that catalyzes the chemical reaction

obtusifoliol + 3 O2 + 3 NADPH + 3 H+ 4alpha-methyl-5alpha-ergosta-8,14,24(28)-trien-3beta-ol + formate + 3 NADP+ + 4 H2O
sterol 14-demethylase
Identifiers
EC number1.14.13.70
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

The 4 substrates of this enzyme are obtusifoliol, O2, NADPH, and H+, whereas its 4 products are 4alpha-methyl-5alpha-ergosta-8,14,24(28)-trien-3beta-ol, formate, NADP+, and H2O.

Ergosterol

Although lanosterol 14α-demethylase is present in a wide variety of organisms, this enzyme is studied primarily in the context of fungi, where it plays an essential role in mediating membrane permeability.[1] In fungi, CYP51 catalyzes the demethylation of lanosterol to create an important precursor that is eventually converted into ergosterol.[2] This steroid then makes its way throughout the cell, where it alters the permeability and rigidity of plasma membranes much as cholesterol does in animals.[3] Because ergosterol constitutes a fundamental component of fungal membranes, many antifungal medications have been developed to inhibit 14α-demethylase activity and prevent the production of this key compound.[3]

Nomenclature

This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of one atom o oxygen into the other donor. The systematic name of this enzyme class is sterol,NADPH:oxygen oxidoreductase (14-methyl cleaving). Other names in common use include obtusufoliol 14-demethylase, lanosterol 14-demethylase, lanosterol 14alpha-demethylase, and sterol 14alpha-demethylase. This enzyme participates in biosynthesis of steroids.[2]

These are not the typical subfamilies, but only one subfamily is created for each major taxonomic group. CYP51A for Animals, CYP51B for Bacteria. CYP51C for Chromista, CYP51D for Dictyostelium, CYP51E for Euglenozoa, CYP51F for Fungi. Those groups with only one CYP51 per species are all called by one name: CYP51A1 is for all animal CYP51s since they are orthologous. The same is true for CYP51B, C, D, E and F. CYP51G (green plants) and CYP51Hs (monocots only so far) have individual sequence numbers.

Function

The biological role of this protein is also well understood. The demethylated products of the CYP51 reaction are vital intermediates in pathways leading to the formation of cholesterol in humans, ergosterol in fungi, and other types of sterols in plants.[4] These sterols localize to the plasma membrane of cells, where they play an important structural role in the regulation of membrane fluidity and permeability and also influence the activity of enzymes, ion channels, and other cell components that are embedded within.[1][5][6] With the proliferation of immuno-suppressive diseases such as HIV/AIDS and cancer, patients have become increasingly vulnerable to opportunistic fungal infections (Richardson et al.). Seeking new means to treat such infections, drug researchers have begun targeting the 14α-demethylase enzyme in fungi; destroying the fungal cell's ability to produce ergosterol causes a disruption of the plasma membrane, thereby resulting in cellular leakage and ultimately the death of the pathogen (DrugBank).

Azoles are currently the most popular class of antifungals used in both agricultural and medical settings.[3] These compounds bind as the sixth ligand to the heme group in CYP51, thereby altering the structure of the active site and acting as noncompetitive inhibitors.[7] The effectiveness of imidazoles and triazoles (common azole subclasses) as inhibitors of 14α-demethylase have been confirmed through several experiments. Some studies test for changes in the production of important downstream ergosterol intermediates in the presence of these compounds.[8] Other studies employ spectrophotometry to quantify azole-CYP51 interactions.[3] Coordination of azoles to the prosthetic heme group in the enzyme's active site causes a characteristic shift in CYP51 absorbance, creating what is commonly referred to as a type II difference spectrum.[9][10]

Prolonged use of azoles as antifungals has resulted in the emergence of drug resistance among certain fungal strains.[3] Mutations in the coding region of CYP51 genes, overexpression of CYP51, and overexpression of membrane efflux transporters can all lead to resistance to these antifungals.[11][12][13][14][15] Consequently, the focus of azole research is beginning to shift towards identifying new ways to circumvent this major obstacle.[3]

Structure

As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes 1H5Z, 1U13, 1X8V, 2BZ9, 2CI0, and 2CIB.

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References
  1. Daum G, Lees ND, Bard M, Dickson R (December 1998). "Biochemistry, cell biology and molecular biology of lipids of Saccharomyces cerevisiae". Yeast. 14 (16): 1471–510. doi:10.1002/(SICI)1097-0061(199812)14:16<1471::AID-YEA353>3.0.CO;2-Y. PMID 9885152.
  2. Lepesheva GI, Waterman MR (March 2007). "Sterol 14alpha-demethylase cytochrome P450 (CYP51), a P450 in all biological kingdoms". Biochimica et Biophysica Acta (BBA) - General Subjects. 1770 (3): 467–77. doi:10.1016/j.bbagen.2006.07.018. PMC 2324071. PMID 16963187.
  3. Becher R, Wirsel SG (August 2012). "Fungal cytochrome P450 sterol 14α-demethylase (CYP51) and azole resistance in plant and human pathogens". Applied Microbiology and Biotechnology. 95 (4): 825–40. doi:10.1007/s00253-012-4195-9. PMID 22684327.
  4. Lepesheva GI, Waterman MR (January 2011). "Structural basis for conservation in the CYP51 family". Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics. 1814 (1): 88–93. doi:10.1016/j.bbapap.2010.06.006. PMC 2962772. PMID 20547249.
  5. Abe F, Usui K, Hiraki T (September 2009). "Fluconazole modulates membrane rigidity, heterogeneity, and water penetration into the plasma membrane in Saccharomyces cerevisiae". Biochemistry. 48 (36): 8494–504. doi:10.1021/bi900578y. PMID 19670905.
  6. "Itraconazole (DB01167)". DrugBank.
  7. Mullins JG, Parker JE, Cools HJ, Togawa RC, Lucas JA, Fraaije BA, Kelly DE, Kelly SL (2011). "Molecular modelling of the emergence of azole resistance in Mycosphaerella graminicola". PLOS ONE. 6 (6): e20973. Bibcode:2011PLoSO...620973M. doi:10.1371/journal.pone.0020973. PMC 3124474. PMID 21738598.
  8. Tuck SF, Patel H, Safi E, Robinson CH (June 1991). "Lanosterol 14 alpha-demethylase (P45014DM): effects of P45014DM inhibitors on sterol biosynthesis downstream of lanosterol". Journal of Lipid Research. 32 (6): 893–902. PMID 1940622.
  9. Vanden Bossche H, Marichal P, Gorrens J, Bellens D, Verhoeven H, Coene MC, Lauwers W, Janssen PA (1987). "Interaction of azole derivatives with cytochrome P-450 isozymes in yeast, fungi, plants and mammalian cells". Pesticide Science. 21 (4): 289–306. doi:10.1002/ps.2780210406.
  10. Yoshida Y, Aoyama Y (January 1987). "Interaction of azole antifungal agents with cytochrome P-45014DM purified from Saccharomyces cerevisiae microsomes". Biochemical Pharmacology. 36 (2): 229–35. doi:10.1016/0006-2952(87)90694-0. PMID 3545213.
  11. Vanden Bossche H, Dromer F, Improvisi I, Lozano-Chiu M, Rex JH, Sanglard D (1998). "Antifungal drug resistance in pathogenic fungi". Medical Mycology. 36 Suppl 1: 119–28. PMID 9988500.
  12. Leroux P, Albertini C, Gautier A, Gredt M, Walker AS (July 2007). "Mutations in the CYP51 gene correlated with changes in sensitivity to sterol 14 alpha-demethylation inhibitors in field isolates of Mycosphaerella graminicola". Pest Management Science. 63 (7): 688–98. doi:10.1002/ps.1390. PMID 17511023.
  13. Sanglard D, Ischer F, Koymans L, Bille J (February 1998). "Amino acid substitutions in the cytochrome P-450 lanosterol 14alpha-demethylase (CYP51A1) from azole-resistant Candida albicans clinical isolates contribute to resistance to azole antifungal agents". Antimicrobial Agents and Chemotherapy. 42 (2): 241–53. doi:10.1128/AAC.42.2.241. PMC 105395. PMID 9527767.
  14. Cannon RD, Lamping E, Holmes AR, Niimi K, Baret PV, Keniya MV, Tanabe K, Niimi M, Goffeau A, Monk BC (April 2009). "Efflux-mediated antifungal drug resistance". Clinical Microbiology Reviews. 22 (2): 291–321, Table of Contents. doi:10.1128/CMR.00051-08. PMC 2668233. PMID 19366916.
  15. Nash A, Rhodes J (2018). "Simulations of CYP51A from Aspergillus fumigatus in a model bilayer provide insights into triazole drug resistance". Medical Mycology. 56 (3): 361–373. doi:10.1093/mmy/myx056. PMID 28992260.

Further reading
  • Bak S, Kahn RA, Olsen CE, Halkier BA (1997). "Cloning and expression in Escherichia coli of the obtusifoliol 14 alpha-demethylase of Sorghum bicolor (L.) Moench, a cytochrome P450 orthologous to the sterol 14 alpha-demethylases (CYP51) from fungi and mammals". Plant J. 11 (2): 191–201. doi:10.1046/j.1365-313X.1997.11020191.x. PMID 9076987.
  • Aoyama Y, Yoshida Y (1991). "Different substrate specificities of lanosterol 14a-demethylase (P-45014DM) of Saccharomyces cerevisiae and rat liver for 24-methylene-24,25-dihydrolanosterol and 24,25-dihydrolanosterol". Biochem. Biophys. Res. Commun. 178 (3): 1064–71. doi:10.1016/0006-291X(91)91000-3. PMID 1872829.
  • Aoyama Y, Yoshida Y (1992). "The 4 beta-methyl group of substrate does not affect the activity of lanosterol 14 alpha-demethylase (P-450(14)DM) of yeast: difference between the substrate recognition by yeast and plant sterol 14 alpha-demethylases". Biochem. Biophys. Res. Commun. 183 (3): 1266–72. doi:10.1016/S0006-291X(05)80327-4. PMID 1567403.
  • Alexander K, Akhtar M, Boar RB, McGhie JF, Barton DH (1972). "The removal of the 32-carbon atom as formic acid in cholesterol biosynthesis". Journal of the Chemical Society, Chemical Communications (7): 383. doi:10.1039/C39720000383.


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