Molecular basis for the antimycotic and antibacterial activity ofN-substituted imidazoles and triazoles: The inhibition of isoprenoid biosynthesis

Autor: Hugo Vanden Bossche, Patrick Marichal, Frans Cornelissen, W. Lauwers, W. Cools, G. Willemsens
Rok vydání: 1984
Předmět:
Zdroj: Pesticide Science. 15:188-198
ISSN: 0031-613X
DOI: 10.1002/ps.2780150210
Popis: The antimycotic N-substituted imidazoles and triazoles, such as imazalil, ketoconazole and itraconazole, interfere selectively at low concentrations (≥0.01nm) with the 14α-demethylase system (which is dependent on cytochrome P-450) of fungal cells, for example, Candida albicans and Penicillium italicum. This results in a decreased availability of ergosterol and the accumulation of 14α-methyl-sterols such as lanosterol. Cholesterol synthesis in a subcellular fraction of rat liver, in intact fibroblasts, and in vivo in rat liver, was much less sensitive, for example, to ketoconazole. The imidazole derivatives imazalil, miconazole, ketoconazole and parconazole, and the triazole derivatives propiconazole, terconazole and itraconazole affect the cytochrome P-450 species of microsomal fractions from Saccharomyces cerevisiae and rat liver. Cytochrome P-450 of rat-liver microsomes was much less sensitive to these azole derivatives, in parallel with the lower sensitivity of cholesterol synthesis. Using unilamellar vesicles composed of phosphatidylcholine, phosphatidyl-ethanolamine and diphosphatidylcholine, multilamellar vesicles of dipalmitoylphos-phatidylcholine, and intact S. cerevisiae, it was shown that the substitution of ergosterol by lanosterol leads to functional changes in the membranes. It is speculated that the selective interaction of the azole derivatives with the yeast microsomal cytochrome P-450 leads to the accumulation of 14a-methyl-sterols and results in changes in the permeability of the membranes and leakages. The observed inhibition of growth may have its origin in these changes. Miconazole, ketoconazole and deacylated ketoconazole (R-39519) also affect the growth of Staphylococcus aureus, miconazole being 12.5 and 14 times, respectively, more active than R-39519 and ketoconazole. The greater antibacterial activity of miconazole coincides with its greater inhibition of the biosynthesis of C-55 isoprenoid alcohol and vitamin K. The phosphorylated derivative of C-55 isoprenoid alcohol has functional importance in the biosynthesis of bacterial cell wall and membrane polymers, and the menaquinone vitamin K plays a role in the electron transport of Gram-positive bacteria. The reduced synthesis of these vital compounds may contribute to the antibacterial activity of miconazole.
Databáze: OpenAIRE
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