Cytochrome P450 Sterol 14α-demethylase Research Articles

Promising Antileishmanial Activity of Micromeria nervosa Essential Oil: In Vitro and In Silico Studies.

The present study aimed to evaluate the leishmanicidal potential of the essential oil (EO) of Micromeria (M.) nervosa and to investigate its molecular mechanism of action by qPCR. Furthermore, in silicointeraction study of the major M. nervosa EO compounds with the enzyme cytochrome P450 sterol 14α-demethylase (CYP51) was also performed. M. nervosa EO was analyzed by gas chromatography-mass spectrometry (GC-MS). Results showed that α-pinene (26.44%), t-cadinol (26.27%), caryophyllene Oxide (7.73 ± 1.04%), and α-Cadinene (3.79 ± 0.12%) are the major compounds of M. nervosa EO. However, limited antioxidant activity was observed, as this EO was ineffective in neutralizing DPPH free radicals and in inhibiting β-carotene bleaching. Interestingly, it displayed effective leishmanicidal potential against promastigote (IC50 of 6.79 and 5.25 μg/mL) and amastigote (IC50 of 8.04 and 7.32 μg/mL) forms of leishmania (L.) infantum and L. major, respectively. Molecular mechanism investigation showed that M. nervosa EO displayed potent inhibition on the thiol regulatory pathway. Furthermore, a docking study of the main components of the EO with cytochrome P450 sterol 14α-demethylase (CYP51) enzyme revealed that t-cadinol exhibited the best binding energy values (-7.5 kcal/mol), followed by α-cadinene (-7.3 kcal/mol) and caryophyllene oxide (-7 kcal/mol). These values were notably higher than that of the conventional drug fluconazole showing weaker binding energy (-6.9 kcal/mol). These results suggest that M. nervosa EO could serve as a potent and promising candidate for the development of alternative antileishmanial agent in the treatment of leishmaniasis.

Isolates of Colletotrichum truncatum with Resistance to Multiple Fungicides from Soybean in Northern Thailand.

In Thailand, four systemic fungicides-carbendazim (Car), azoxystrobin (Azo), difenoconazole (Dif), and penthiopyrad (Pen)-are commonly used to control soybean anthracnose caused by Colletotrichum truncatum; however, the pathogen has developed resistance. From 2019 to 2020, fungicide resistance in C. truncatum from fields in Chiang Rai and Chiang Mai was monitored. In tests of 85 C. truncatum isolates for resistance to multiple fungicides, 15.3% were CarRAzoR, 34.1% were triple resistant (CarRAzoRDifR or CarRAzoRPenR), and 50.6% were CarRAzoRDifRPenR. Surprisingly, all isolates tested had lost their sensitivity to one or more of the fungicides tested. The carbendazim-resistant isolates carried a point mutation in the β-tubulin gene at codon 198 (E198A) or 200 (F200Y), and all azoxystrobin-resistant isolates had a mutation in the cytochrome b gene at codon 143 (G143A) or 129 (F129L). Moreover, a novel mutation at codon 208 (S208Y) in the gene encoding succinate dehydrogenase subunit B was detected in all of the isolates highly resistant to penthiopyrad. No mutation linked with difenoconazole resistance was detected in the genes encoding cytochrome P450 sterol 14α-demethylase. To the best of our knowledge, this is the first report of C. truncatum isolates resistant to multiple fungicides and serves as a warning to take measures to prevent the occurrence and distribution of these multiple-fungicide-resistant populations in soybean fields.

Structural modeling of cytochrome P450 51 from a deep-sea fish points to a novel structural feature in other CYP51s

Cytochromes P450 (CYP), enzymes involved in the metabolism of endogenous and xenobiotic substrates, provide an excellent model system to study how membrane proteins with unique functions have catalytically adapted through evolution. Molecular adaptation of deep-sea proteins to high hydrostatic pressure remains poorly understood. Herein, we have characterized recombinant cytochrome P450 sterol 14α-demethylase (CYP51), an essential enzyme of cholesterol biosynthesis, from an abyssal fish species, Coryphaenoides armatus. C. armatus CYP51 was heterologously expressed in Escherichia coli following N-terminal truncation and purified to homogeneity. Recombinant C. armatus CYP51 bound its sterol substrate lanosterol giving a Type I binding spectra (KD 15 μM) and catalyzed lanosterol 14α-demethylation turnover at 5.8 nmol/min/nmol P450. C. armatus CYP51 also bound the azole antifungals ketoconazole (KD 0.12 μM) and propiconazole (KD 0.54 μM) as determined by Type II absorbance spectra. Comparison of C. armatus CYP51 primary sequence and modeled structures with other CYP51s identified amino acid substitutions that may confer an ability to function under pressures of the deep sea and revealed heretofore undescribed internal cavities in human and other non-deep sea CYP51s. The functional significance of these cavities is not known. PrologueThis paper is dedicated in memory of Michael Waterman and Tsuneo Omura, who as good friends and colleagues enriched our lives. They continue to inspire us.

Status of Fungicide Resistance and Physiological Characterization of Tebuconazole Resistance in Rhizocotonia solani in Sichuan Province, China.

The resistance prevalence of chemical fungicides has caused increasingly serious agro-ecological environmental problems. However, there are few previous reports about resistance to succinate dehydrogenase (SDHI) or sterol demethylation inhibitor (DMI) in Rhizoctonia solani, one of the main agro-diseases. In this study, the fungicide resistance of 122 R. solani isolates in Sichuan Province was monitored by the mycelial growth rate method. Results showed that all isolates were susceptible to hexaconazole and most isolates were susceptible to thifluzamide, except for the field isolate MSRS-2-7 due to a moderate resistance to thifluzamide (16.43-fold resistance ratio, RR), compared to the sensitivity baseline of thifluzamide (0.042 μg/mL EC50 values). On the contrary, many isolates showed moderate or high resistance to tebuconazole (10.59- to 60.78-fold RR), reaching EC50 values of 0.54~3.10 μg/mL, especially for a highly resistant isolate LZHJ-1-8 displaying moderate resistance to epoxiconazole (35.40-fold RR due to a 3.54 μg/mL EC50 value). The fitness determination found that the tebuconazole-resistant isolates showed higher fitness cost with these characteristics, including a lower growth rate, higher relative electric conductivity, an increased ability to tolerate tebuconazole, and high osmotic pressure. Four new mutations of cytochrome P450 sterol 14α-demethylase (CYP51), namely, S94A, N406S, H793R, and L750P, which is the target for DMI fungicides, was found in the tebuconazole-resistant isolates. Furthermore, the lowest binding energy with tebuconazole was also found in the LZHJ-1-8 isolate possessing all the mutations through analyses with Discovery Studio software. Therefore, these new mutation sites of CYP51 may be linked to the resistance against tebuconazole, and its application for controlling R. solani should be restricted in some areas.

A Botybirnavirus Isolated from Alternaria tenuissima Confers Hypervirulence and Decreased Sensitivity of Its Host Fungus to Difenoconazole

Alternaria alternata botybirnavirus 1 (AaBRV1) was isolated from a strain of Alternaria alternata, causing watermelon leaf blight in our previous research. The effect of AaBRV1 on the phenotype of its host fungus, however, was not determined. In the present study, a novel strain of AaBRV1 was identified in A. tenuissima strain TJ-NH-51S-4, the causal agent of cotton Alternaria leaf spot, and designated as AaBRV1-AT1. A mycovirus AaBRV1-AT1-free strain TJ-NH-51S-4-VF was obtained by protoplast regeneration, which eliminated AaBRV1-AT1 from the mycovirus AaBRV1-AT1-infected strain TJ-NH-51S-4. Colony growth rate, spore production, and virulence of strain TJ-NH-51S-4 were greater than they were in TJ-NH-51S-4-VF, while the sensitivity of strain TJ-NH-51S-4 to difenoconazole, as measured by the EC50, was lower. AaBRV1-AT1 was capable of vertical transmission via asexual spores and horizontal transmission from strain TJ-NH-51S-4 to strain XJ-BZ-5-1hyg (another strain of A. tenuissima) through hyphal contact in pairing cultures. A total of 613 differentially expressed genes (DEGs) were identified in a comparative transcriptome analysis between TJ-NH-51S-4 and TJ-NH-51S-4-VF. Relative to strain TJ-NH-51S-4-VF, the number of up-regulated and down-regulated DEGs in strain TJ-NH-51S-4 was 286 and 327, respectively. Notably, the expression level of one DEG-encoding cytochrome P450 sterol 14α-demethylase and four DEGs encoding siderophore iron transporters were significantly up-regulated. To our knowledge, this is the first documentation of hypervirulence and reduced sensitivity to difenoconazole induced by AaBRV1-AT1 infection in A. tenuissima.

Transcriptome and lipidomics profiling of F2 generation female Chinese sturgeon (Acipenser sinensis) in response to different arachidonic acid diets

Our previous study indicated that dietary arachidonic acid (ARA) inclusion levels higher than 1% in the diet play key roles in ARA deposition, steroid and vitellogenin (Vtg) synthesis in F2 generation female Chinese sturgeon, but the regulatory mechanism remains to be elucidated. As follow-up to our previous study (Aquaculture Reports, 21, 100818), the study further aimed to investigate the possible mechanisms of the effects of dietary ARA promoted steroid hormone synthesis in the ovary by transcriptomics and in the serum by lipidomics. RNA-Seq and lipidomics technology were employed to profile the ovary transcriptome and serum lipidomics after feeding four ARA supplemented diets (named CT, LT, MT and HT), and the differentially expressed genes (DEGs) and key differential metabolites were identified. A total of 1018 DEGs, 853 DEGs, 2680 DEGs, 303 DEGs, 1185 DEGs and 409 DEGs were identified in the LT versus CT, MT versus CT, HT versus CT, MT versus LT, HT versus LT and HT versus MT comparisions, respectively. Gene ontology showed that the DEGS between the ARA-supplemented diet group and the unsupplemented diet group were enriched in regulation of cellular process, development process and reproduction. Pathways concerning steroid hormone biosynthesis and cholesterol biosynthesis in lipid metabolism and ovarian steroidogenesis as well as the nuclear-initiated estrogen signaling pathway in endocrine system were enriched. Furthermore, weighted correlation network analysis (WGCNA) identified six hub genes that regulate gonad development and cholesterol synthesis, namely, mitogen-activated protein kinase (MAPK14), cyclin-dependent kinase 2 (CDK2), heat shock protein 8 (HSPA8), two forkhead boxes (FOXP3 and FOXJ3) and cytochrome P450 sterol 14α-demethylase (CYP51A1). Collectively, the molecular mechanism by which ARA regulates the synthesis of steroids, may be related to enhanced cholesterol ester metabolism and facilitation of steroidogenesis gene transcription, which ultimately benefits ovary development in F2 generation Chinese sturgeon.

Lack of an Intron in Cytochrome b and Overexpression of Sterol 14α-Demethylase Indicate a Potential Risk for QoI and DMI Resistance Development in Neophysopella spp. on Grapes.

Asian grapevine leaf rust, caused by Neophysopella meliosmae-myrianthae and N. tropicalis, is often controlled by quinone outside inhibitor (QoI) and demethylation inhibitor (DMI) fungicides in Brazil. Here, we evaluated the sensitivity of 55 Neophysopella spp. isolates to pyraclostrobin (QoI) and tebuconazole (DMI). To elucidate the resistance mechanisms, we analyzed the sequences of the cytochrome b (CYTB) and cytochrome P450 sterol 14α-demethylase (CYP51) target proteins of QoI and DMI fungicides, respectively. The CYP51 expression levels were also determined in a selection of isolates. In leaf disc assays, the mean 50% effective concentration (EC50) value for pyraclostrobin was about 0.040 µg/ml for both species. CYTB sequences were identical among all 55 isolates, which did not contain an intron immediately after codon 143. No amino acid substitution was identified at codons 129, 137, and 143. The mean EC50 value for tebuconazole was 0.62 µg/ml for N. tropicalis and 0.46 µg/ml for N. meliosmae-myrianthae, and no CYP51 sequence variation was identified among isolates of the same species. However, five N. meliosmae-myrianthae isolates grew on leaf discs treated at 10 µg/ml tebuconazole, and these were further exposed to tebuconazole selection pressure. Tebuconazole-adapted laboratory isolates of N. meliosmae-myrianthae showed an eight- to 25-fold increase in resistance after four rounds of selection that was not associated with CYP51 targetalterations. In comparison with sensitive isolates, CYP51 expression was induced in the presence of tebuconazole in three out of four tebuconazole-adapted isolates tested. These results suggest a potential risk for QoI and DMI resistance development in Neophysopella spp.

No Evidence of Resistance to Trifloxystrobin, Triflumizole, and Boscalid in Podosphaera leucotricha Isolates From U.S. Commercial Apple Orchards.

Apple powdery mildew, caused by Podosphaera leucotricha, continues to be a challenge in commercial apple orchards in the U.S. Pacific Northwest and worldwide. In this study, P. leucotricha isolates were collected in 2018 and 2019 from two organic (baseline) and eight conventional (exposed) apple orchards in Washington, New York, and Virginia, and assessed for their sensitivity to trifloxystrobin (TRI, n = 232), triflumizole (TFZ, n = 217), and boscalid (BOS, n = 240) using a detached leaf assay. Effective concentrations inhibiting 50% growth (EC50) were not significantly different between baseline and exposed isolates, and ranged from 0.001 to 0.105, 0.09 to 6.31, and 0.05 to 2.18 µg/ml, for TRI, TFZ, and BOS, respectively. Reduction in sensitivity by factors of 105, 63, and 22 to TRI, TFZ, and BOS, respectively, were observed in some isolates, but all isolates were controlled by the commercial label rates of the three fungicides on detached leaves. Sequencing of the cytochrome b (cytb), cytochrome P450 sterol 14α-demethylase (CYP51), and the iron-sulfur protein subunit (SdhB) genes in isolates with high EC50 revealed no mutation previously reported to confer resistance to these fungicides in other fungi, and presence of a group I intron after codon 143 in the cytb gene. Significant (P < 0.001) moderate positive correlations (r = 0.38) observed between sensitivity to TRI and TFZ warrant continuous rotations of fungicides with different modes of action in conventional orchards. The established baseline sensitivities and the molecular markers will help in selecting discriminatory doses and bypassing the challenging invivo testing for future sensitivity monitoring in P. leucotricha.

Copper(II) and Zinc(II) Complexes with the Clinically Used Fluconazole: Comparison of Antifungal Activity and Therapeutic Potential.

Copper(II) and zinc(II) complexes with clinically used antifungal drug fluconazole (fcz), {[CuCl2(fcz)2].5H2O}n, 1, and {[ZnCl2(fcz)2]·2C2H5OH}n, 2, were prepared and characterized by spectroscopic and crystallographic methods. The polymeric structure of the complexes comprises four fluconazole molecules monodentately coordinated via the triazole nitrogen and two chlorido ligands. With respect to fluconazole, complex 2 showed significantly higher antifungal activity against Candida krusei and Candida parapsilosis. All tested compounds reduced the total amount of ergosterol at subinhibitory concentrations, indicating that the mode of activity of fluconazole was retained within the complexes, which was corroborated via molecular docking with cytochrome P450 sterol 14α-demethylase (CYP51) as a target. Electrostatic, steric and internal energy interactions between the complexes and enzyme showed that 2 has higher binding potency to this target. Both complexes showed strong inhibition of C. albicans filamentation and biofilm formation at subinhibitory concentrations, with 2 being able to reduce the adherence of C. albicans to A549 cells in vitro. Complex 2 was able to reduce pyocyanin production in Pseudomonas aeruginosa between 10% and 25% and to inhibit its biofilm formation by 20% in comparison to the untreated control. These results suggest that complex 2 may be further examined in the mixed Candida-P. aeruginosa infections.

Synthesis, characterization, molecular docking and antimicrobial activity of copper(II) complexes of metronidazole and 1,10 phenanthroline

Three new compounds containing mono- and dinuclear Cu(II) complexes, [Cu(Met)2Cl2]2, Cu(H2O)(Met)2Cl]2 and [Cu(H2O)(phen)2]NO3 (Met = metronidazole; Phen = 1,10-phenathroline) have been synthesized and characterized by Infra-Red, UV–Vis, Single Crystal X-ray analyses, Thermogravimetric techniques and Scanning electron micrography. The biological activities of the complexes were evaluated against a series of Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii); Gram-positive (Enterococcus faecium, Bacillus cereus and Staphylococcus aureus) strains as well as the yeasts (Candida albicans and Cryptococcus neoformans). Density-functional theory (DFT) studies revealed that compound [Cu(Met)2Cl2]2 is less stable in comparison to compounds, [Cu(H2O)(phen)2]NO3 and [Cu(H2O)(Met)2Cl]2. Docking studies of Cu(II) complexes with DNA structure (PDB id 1ZEW) found drug activity by groove binding. Binding mode of Cu(II) complexes with (i) fungal cytochrome P450 sterol 14α-demethylase (CYP51), which facilitates the synthesis of ergosterol in fungi; (ii) 4HL2; a New Delhi metallo-β-lactamase-1 (NDM-1) produced by strains of K. pneumoniae and (iii) 4M7U; an enzyme dihydrofolate reductase (DHFR) responsible for E. faecium activity and bacterial growth was established via docking studies. In general, [Cu(Met)2Cl2]2 was the most broad-spectrum antimicrobial compound, indicating an important role of electron-withdrawing substituents such as chlorine and suggest their potential application as antibacterial agents. The findings should be helpful in the development of antimicrobial drugs of Cu(II) complexes of metronidazole and 1,10 phenanthroline.

Design and Synthesis of New Antifungals Based on N-Un-substituted Azoles as 14α Demethylase Inhibitor

Azole antifungal agents, which are widely used as antifungal antibiotics, inhibit cytochrome P450 sterol 14α-demethylase (CYP51). Nearly all azole antifungal agents are Nsubstituted azoles. In addition, an azolylphenalkyl pharmacophore is uniquely shared by all azole antifungals. Due to the importance of nitrogen atom of azoles (N-3 of imidazole and N-4 of triazole) in coordination with heme in the binding site of the enzyme, here a group of N- un-substituted azoles in which both nitrogen are un-substituted was reported. Designed compounds were synthesized by the reaction of imidazole-4- carboxaldehyde with appropriate arylamines and subsequently reduced to desired amine derivatives. Antifungal activity against Candida albicans and Saccharomyces cervisiae was done using a broth micro-dilution assay. Docking studies were done using AutoDock. Antimicrobial evaluation revealed that some of these compounds exhibited moderate antimicrobial activities against tested pathogenic fungi, wherein compounds 3, 7, and 8 were potent. Docking studies propose that all of the prepared azoles interacted with 14α-DM, wherein azoleheme coordination played the main role in drug-receptor interaction. Our results offer some useful references for molecular design performance or modification of this series of compounds as a lead compound to discover new and potent antimicrobial agents.

Characterization of difenoconazole resistance in Lasiodiplodia theobromae from papaya in Brazil.

Stem-end rot caused by Lasiodiplodia theobromae is one of the most important diseases of papaya in northeastern Brazil. It can be controlled effectively by demethylation inhibitor (DMI) fungicides, but the occurrence of DMI resistance may decrease fungicide efficacy. Detached fruit studies revealed that isolates with EC50 values of 6.07 and 6.28 μg mL-1 were not controlled effectively, but reduced virulence and ability to grow at temperatures ranging from 12 to 32 °C suggesting fitness penalties were observed. Cross-resistance was observed only between difenoconazole and propiconazole. The entire cytochrome P450 sterol 14α-demethylase (LtCYP51) gene and its flanking regions were cloned. The gene was 1746 bp in length and contained three introns. The predicted protein contained 525 amino acids. Phylogenetic tree analysis showed that the LtCYP51 belongs to the CYP51B clade. No amino acid variation was found between sensitive and resistant isolates; however, the gene was constitutively more highly expressed in resistant isolates. Resistance to DMI fungicides in L. theobromae is based on LtCYP51 gene overexpression and fitness penalties may be present in difenoconazole-resistant isolates. © 2019 Society of Chemical Industry.

Molecular simulations of fluconazole-mediated inhibition of sterol biosynthesis

Invasive opportunistic fungal infections and antifungal drug resistance prompt the investigation of the underlying molecular mechanisms of the inhibition of the triazole drugs. The target of triazoles is the product of the ERG11 gene, the cytochrome P450 sterol 14α-demethylase (CYP51), which is part of the ergosterol biosynthetic pathway. In this study, molecular dynamics (MD) simulations were performed to reveal the mechanisms of fluconazole inhibitory activities in orthologs of CYP51 present in humans (Hs), and in Mycobacterium tuberculosis (Mt), Candida albicans (Ca) and Candida glabrata (Cg). The conformational diversity of the BC loop in the CYP51-Hs and CYP51-Mt structures alter the catalytic site of these enzymes when compared to the fungal CYPs, resulting in greater conformational variability of the inhibitor. Overall interaction energies are consistent with the observed affinities, but are the result of the competitive interactions of the ligand with the protein residues, the HEME group and water molecules. Specifically, protein–fluconazole interactions are more effective in CYP51-Mt due to polar interactions with the Arg96 residue. These interactions are, however, substituted in fungal enzymes by ligand–HEME interactions, which compensate for the loss of the polar bond and result in a more energetically favored binding. Therefore, the development of ligand with increased specificity to fungal enzymes should focus on the strengthening polar ligand–HEME interactions, while larger hydrophobic ligands are probably best suited to target mycobacterial and human enzymes. These differences and other ligand-binding site-specific interactions are presented and can inspire the design of new inhibitors with greater ortholog specificity.

Clinical Candidate VT-1161's Antiparasitic Effect In Vitro , Activity in a Murine Model of Chagas Disease, and Structural Characterization in Complex with the Target Enzyme CYP51 from Trypanosoma cruzi

A novel antifungal drug candidate, the 1-tetrazole-based agent VT-1161 [(R)-2-(2,4-difluorophenyl)-1,1-difluoro-3-(1H-tetrazol-1-yl)-1-{5-[4-(2,2,2-trifluoroethoxy)phenyl]pyridin-2-yl}propan-2-ol], which is currently in two phase 2b antifungal clinical trials, was found to be a tight-binding ligand (apparent dissociation constant [Kd], 24 nM) and a potent inhibitor of cytochrome P450 sterol 14α-demethylase (CYP51) from the protozoan pathogen Trypanosoma cruzi. Moreover, VT-1161 revealed a high level of antiparasitic activity against amastigotes of the Tulahuen strain of T. cruzi in cellular experiments (50% effective concentration, 2.5 nM) and was active in vivo, causing >99.8% suppression of peak parasitemia in a mouse model of infection with the naturally drug-resistant Y strain of the parasite. The data strongly support the potential utility of VT-1161 in the treatment of Chagas disease. The structural characterization of T. cruzi CYP51 in complex with VT-1161 provides insights into the molecular basis for the compound's inhibitory potency and paves the way for the further rational development of this novel, tetrazole-based inhibitory chemotype both for antiprotozoan chemotherapy and for antifungal chemotherapy.

Homology modeling of Candida Albicans lanosterol 14 ?- demethylase and validation of the homology model.

The cytochrome P450 sterol 14α-demethylase enzyme (CYP51) is the target of azole antifungals. Azoles block ergosterol synthesis, and thereby inhibit fungal growth, by binding in the active-site cavity of the enzyme and ligating the iron atom of the heme cofactor through a nitrogen atom of the azole.In this work, homology models of the CYP51 enzymes from Candida albicans were constructed based on the X-ray crystal structure of CYP51 from Saccharomyces cerevisiae .

Structure-Functional Characterization of Cytochrome P450 Sterol 14α-Demethylase (CYP51B) from Aspergillus fumigatus and Molecular Basis for the Development of Antifungal Drugs

Aspergillus fumigatus is the opportunistic fungal pathogen that predominantly affects the immunocompromised population and causes 600,000 deaths/year. The cytochrome P450 51 (CYP51) inhibitor voriconazole is currently the drug of choice, yet the treatment efficiency remains low, calling for rational development of more efficient agents. A. fumigatus has two CYP51 genes, CYP51A and CYP51B, which share 59% amino acid sequence identity. CYP51B is expressed constitutively, whereas gene CYP51A is reported to be inducible. We expressed, purified, and characterized A. fumigatus CYP51B, including determination of its substrate preferences, catalytic parameters, inhibition, and x-ray structure in complexes with voriconazole and the experimental inhibitor (R)-N-(1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethyl)-4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamide (VNI). The enzyme demethylated its natural substrate eburicol and the plant CYP51 substrate obtusifoliol at steady-state rates of 17 and 16 min(-1), respectively, but did not metabolize lanosterol, and the topical antifungal drug miconazole was the strongest inhibitor that we identified. The x-ray crystal structures displayed high overall similarity of A. fumigatus CYP51B to CYP51 orthologs from other biological kingdoms but revealed phylum-specific differences relevant to enzyme catalysis and inhibition. The complex with voriconazole provides an explanation for the potency of this relatively small molecule, whereas the complex with VNI outlines a direction for further enhancement of the efficiency of this new inhibitory scaffold to treat humans afflicted with filamentous fungal infections.

Design and Antimicrobial Evaluation of 1-Methylimidazole Derivatives as New Antifungal and Antibacterial Agents

Azole antifungal agents, which are widely used as antifungal antibiotics, inhibit cytochrome P450 sterol 14α-demethylase (CYP51). In this research, a group of 1-methylimidazole derivatives were synthesized for evaluation as antibacterial and antifungal agents. Antimicrobial evaluation revealed that some of these compounds exhibited significant antimicrobial activities against tested pathogenic fungi and bacteria, wherein compounds 3 and 8 were most potent. To find the action mechanism, all of these compounds were subjected to docking studies using the AutoDock 4.2 program. The results show that all of the azoles (2 – 5, 7, and 8) interacted with 14α-DM, wherein azole – heme coordination, hydrogen binding, and -cation interactions were involved in the drug – receptor interaction. These studies offer some useful references in order to understand the action mechanism; moreover, performing the molecular design or modification of this series as a lead compound can assist in identifying new and potent antimicrobial agents.

Homology modeling of lanosterol 14α-demethylase of Candida albicans and insights into azole binding

Candida albicans is one of the most common causes of invasive fungal infections. Azole antifungal agents are widely used as fungal antibiotics which inhibit the cytochrome P450 sterol 14α-demethylase (CYP51). This study describes the homology modeling and three-dimensional model of CYP51 from C. albicans SC5314. Dope score, GA341 of Modeller, PROCHECK statistics, Ramachandran, and G-factors were used to analyze and evaluate a final model. Molecular docking identified the binding mode of the azole antifungal agents with modeled CYP51. The obtained results of Autodock program, compounds 1–4, were determined the heterocyclic nitrogen atom of azole bound to the heme iron atom in the binding site of the enzyme. Based on the results of this study, we conclude that the structural model of C. albicans SC5314 can be used in azole optimization, virtual screening and de novo inhibitor design for the discovery of new antifungal agents. This study describes the homology modeling and three-dimensional model of CYP51 from C. albicans SC5314. Dope score and GA341 of Modeller, and PROCHECK statistics, Ramachandran, and G-factors were used to analysis and evaluate of the final model.

Shape and pharmacophore-based virtual screening to identify potential cytochrome P450 sterol 14α-demethylase inhibitors

Sterol 14α-demethylase (CYP51) is a cytochrome P450 heme thiolate containing enzyme involved in biosynthesis of membrane sterols, including sterol in animals, ergosterol in fungi, and a variety of C24-modified sterols in plants and protozoa. Several clinical drugs have been developed to reduce the impact of fungal diseases, but their clinical uses have been limited by the emergence of drug resistance and insufficiencies in their antifungal activity. Therefore, in order to identify potential CYP51 inhibitors, we have implemented a virtual screening (VS) protocol by using both phase shape and pharmacophore model (AHHRR) against Asinex, ChemBridge and Maybridge databases. A filtering protocol, including Lipinski filter, number of rotatable bonds and different precisions of molecular docking was applied in hits selection. The results indicated that both shape-based and pharmacophore-based screening yielded the best result with potential inhibitors. The searched compounds were also evaluated with ADME properties, which show excellent pharmacokinetic properties under the acceptable range. We identified potential CYP51 inhibitors for further investigation, they could also be employed to design ligands with enhanced inhibitory potencies and to predict the potencies of analogs to guide synthesis/or prepare synthetic antifungal analogs against CYP51.

Induced overexpression of cytochrome P450 sterol 14α-demethylase gene (CYP51) correlates with sensitivity to demethylation inhibitors (DMIs) inSclerotinia homoeocarpa

The fungus Sclerotinia homoeocarpa causes dollar spot, the most important turfgrass disease worldwide. Demethylation inhibitor (DMI) fungicides have been relied upon heavily to manage this disease. Presently, populations of S. homoeocarpa with reduced sensitivity or resistance to DMIs are widespread in the United States. Cytochrome P450 sterol 14α-demethylase (ShCYP51) and its flanking regions were identified and sequenced in 29 isolates of S. homoeocarpa with a range of DMI sensitivities. No modifications were found in the gene coding and upstream regions that were consistently related to DMI sensitivity. In the absence of propiconazole, ShCYP51 was expressed at a similar low level among DMI baseline and resistant isolates. In the presence of propiconazole, DMI-resistant isolates were induced to express ShCYP51 at significantly higher levels than baseline isolates by propiconazole at 5 mg L(-1) for 5 h or at 0.5 mg L(-1) for 72 h. The ShCYP51 expression level after 72 h exposure to 0.5 mg L(-1) of propiconazole was linearly related to EC50 values and ΔRG (the change in relative growth rate over time), with R(2) values equal to 83.7 and 90.0% respectively. Induced overexpression of ShCYP51 in resistant isolates following DMI exposure is an important factor determining DMI sensitivity in S. homoeocarpa.