14-a-demethylase

The answer is a. (Hardman, p 1180. Katzung, pp 817—819J Fluconazole indirectly inhibits ergosterol synthesis. It inhibits cytochrome P4.50, which is a key enzyme system for cytochrome P4.5O-dependent sterol 14-a-demethylase. This leads to accumulation of 14-a-sterols, resulting in impairment of the cytoplasmic membrane. 

Mode of action Ketoconazole interacts with C-14 a-demethylase (a cytochrome P-450 enzyme) to block demethylation of lanosterol to ergosterol, the principal sterol of fungal membranes Figure 34.4). This inhibition disrupts membrane function and increases permeability. Ketoconazole acts in an additive manner with flucytosine against Candida, but antagonizes amphotericin B s antifungal activity. 

Bak, S., Kahn, R.A., Olsen, C.E. and Halkier, B.A. (1997) Cloning and expression in Escherichia coil of the obtusifoliol 14 a-demethylase of Sorghum bicolor (L.) Moench, a cytochrome P450 orthologous to the sterol 14 a-demethylases (CYP51) from fungi and mammals. Plant., 11,191-201. 

Taton, M. and Rahier, A. (1991) Properties and structural requirements for substrate specificity of cytochrome P450-dependent obtusifoliol 14 a-demethylase from maize Zea mays) seedlings. Biochem.., TUI, 483-92. 

Molecular Analysis of Sterol 14 a Demethylase Gene from Barley... 

Figure 2. Southern analysis of mildew DNA restriction digests probed with plasmid pUC8 containing the sterol 14 a demethylase sequence from yeast, (pDC8-2860H), the whole coding sequence (A), 3 end (B) and 5 end (C).

Lanosterol 14-a demethylase MCSS/Ludi Probe mapping + fragment linking [106]... 

Yes, in high doses or with prolonged therapy. The decrease in cholesterol synthesis can affect the synthesis of steroid hormones. Additionally, the drug inhibits key enzymes in hormone biosynthesis, such as 14-a demethylase and 11-(3 hydroxylase, resulting in lower levels of androgens. 

Azoles are fungicidal and interfere with the synthesis of ergosterol by inhibiting 14-a-demethylase, a fungal P450 enzyme, which converts lanosterol to ergosterol... 

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