Article

Detailed Mechanism of Squalene Epoxidase Inhibition by Terbinafine

BioInfoBank Institute, Poznań, Poland.
Journal of Chemical Information and Modeling (Impact Factor: 4.07). 02/2011; 51(2):455-62. DOI: 10.1021/ci100403b
Source: PubMed

ABSTRACT Squalene epoxidase (SE) is a key flavin adenine dinucleotide (FAD)-dependent enzyme of ergosterol and cholesterol biosynthetic pathways and an attractive potential target for drugs used to inhibit the growth of pathogenic fungi or to lower cholesterol level. Although many studies on allylamine drugs activity have been published during the last 30 years, up until now no detailed mechanism of the squalene epoxidase inhibition has been presented. Our study brings such a model at atomic resolution in the case of yeast Saccharomyces cerevisiae . Presented data resulting from modeling studies are in excellent agreement with experimental findings. A fully atomic three-dimensional (3D) model of squalene epoxidase (EC 1.14.99.7) from S. cerevisiae was built with the help of 3D-Jury approach and further screened based on data known from mutation experiments leading to terbinafine resistance. Docking studies followed by molecular dynamics simulations and quantum interaction energy calculations [MP2/6-31G(d)] resulted in the identification of the terbinafine-squalene epoxidase mode of interaction. In the energetically most likely orientation of terbinafine its interaction energy with the protein is ca. 120 kJ/mol. In the favorable position the terbinafine lipophilic moiety is located vertically inside the squalene epoxidase binding pocket with the tert-butyl group oriented toward its center. Such a position results in the SE conformational changes and prevents the natural substrate from being able to bind to the enzyme's active site. That would explain the noncompetitive manner of SE inhibition. We found that the strongest interaction between terbinafine and SE stems from hydrogen bonding between hydrogen-bond donors, hydroxyl group of Tyr90 and amine nitrogen atom of terbinafine. Moreover, strong attractive interactions were recorded for amino acids whose mutations resulted in terbinafine resistance. Our results, elucidating at a molecular level the mode of terbinafine inhibitory activity, can be utilized in designing more potent or selective antifungal drugs or even medicines lowering cholesterol in humans.

Download full-text

Full-text

Available from: Dariusz Plewczynski, Apr 10, 2015
1 Follower
 · 
156 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Squalene monooxygenase catalyzes the epoxidation of C-C double bond of squalene to yield 2,3-oxidosqualene, the key step of sterol biosynthesis pathways in Eukaryotes. Sterols are essential compounds of these organisms and squalene epoxidation is an important regularory point in their synthesis. Squalene monooxygenase down regulation in vertebras and fungi decreases synthesis of cholesterol and ergosterol, respectively, which makes squalene monooxygenase the potent and attractive target of hypercholesterolemia and antifungal therapies. Currently some fungal squalene monooxygenase inhibitors (terbinafine, naftifine, butenafine) are in clinical use, whereas mammalian enzymes' inhibitors are still under investigation. An enormous scale of hypercholesterolemia and a lack of both sufficient and safe remedies make researches on new squalene monooxygenase inhibitors so urgent and up-to-date. In this paper we (i) review data on activity and the structure of squalene monooxygenase, (ii) present its inhibitors (iii) compare current strategies of lowering cholesterol level in blood with a selection of the most promising, (iv) underline advantages of squalene monooxygenase as a good target for hypercholesterolemia therapy, and (v) discuss safety concerns about hypercholesterolemia therapy based on inhibition of cellular cholesterol biosynthesis and potential usage of squalene monooxygenase inhibitors in clinical practice. After many years of use statin there are some clinical evidences for their adverse effects and only partial effectiveness. Currently they are drugs of choice used with many restrictions especially in case of children, old patients, women of childbearing potential. Certainly, for the next few years, statins will continue to be suitable tool for cost-effective cardiovascular prevention, however researches on new hypolipidemic drugs are highly desirable. We suggest that squalene monooxygenase inhibitors have a big chance to become the hypocholesterolemic agents of the future.
    Biological Chemistry 10/2011; 392(12). DOI:10.1515/BC-2011-195 · 2.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Squalene monooxygenase catalyzes the epoxidation of C-C double bond of squalene to yield 2,3-oxidosqualene, the key step of sterol biosynthesis pathways in eukaryotes. Sterols are essential compounds of these organisms and squalene epoxidation is an important regulatory point in their synthesis. Squalene monooxygenase downregulation in vertebrates and fungi decreases synthesis of cholesterol and ergosterol, respectively, which makes squalene monooxygenase a potent and attractive target of hypercholesterolemia and antifungal therapies. Currently some fungal squalene monooxygenase inhibitors (terbinafine, naftifine, butenafine) are in clinical use, whereas mammalian enzymes' inhibitors are still under investigation. Research on new squalene monooxygenase inhibitors is important due to the prevalence of hypercholesterolemia and the lack of both sufficient and safe remedies. In this paper we (i) review data on activity and the structure of squalene monooxygenase, (ii) present its inhibitors, (iii) compare current strategies of lowering cholesterol level in blood with some of the most promising strategies, (iv) underline advantages of squalene monooxygenase as a target for hypercholesterolemia therapy, and (v) discuss safety concerns about hypercholesterolemia therapy based on inhibition of cellular cholesterol biosynthesis and potential usage of squalene monooxygenase inhibitors in clinical practice. After many years of use of statins there is some clinical evidence for their adverse effects and only partial effectiveness. Currently they are drugs of choice but are used with many restrictions, especially in case of children, elderly patients and women of childbearing potential. Certainly, for the next few years, statins will continue to be a suitable tool for cost-effective cardiovascular prevention; however research on new hypolipidemic drugs is highly desirable. We suggest that squalene monooxygenase inhibitors could become the hypocholesterolemic agents of the future.
    Biological Chemistry 12/2011; 392(12):1053-75. DOI:10.1515/BC.2011.195 · 2.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pneumocystis pneumonia (PCP) remains a leading opportunistic infection in patients with weakened immune system. The fungus causing the infection belongs to the genus, Pneumocystis, and its members are found in a large variety of mammals. Adaptation to the lung environment of a host with an intact immune system has been a key to its successful survival. Unfortunately, the metabolic strategies used by these fungi to grow and survive in this context are largely unknown. There were considerable impediments to standard approaches for investigation of this unique pathogen, the most problematic being the lack of a long term in vitro culture system. The absence of an ex vivo cultivation method remains today, and many fundamental scientific questions about the basic biology, metabolism, and life cycle of Pneumocystis remain unanswered. Recent progress in sequencing of the Pneumocystis carinii genome, a species infecting rats, permitted a more informative search for genes and biological pathways within this pathogen that are known to be targets for existing antifungal agents. In this work, we review the classes of antifungal drugs with respect to their potential applicability to the treatment of PCP. Classes covered in the review are the azoles, polyenes, allylamines, and echinocandins. Factors limiting the use of standard antifungal treatments and the currently available alternatives (trimethoprim-sulfamethoxazole, atovaquone, and pentamidine) are discussed. A summary of genomic sequences within Pneumocystis carinii associated with the corresponding targeted biological pathways is provided. All sequences are available via Pneumocystis Genome Project at http://pgp.cchmc.org/
    Current drug targets 08/2012; DOI:10.2174/138945012803530107 · 3.60 Impact Factor