Sterol 14alpha-demethylase (CYP51)

Sterol 14alpha-demethylase (CYP51) is a highly conserved cytochrome P450 enzyme found in fungi, animals, and plants, where it acts as a key step in the biosynthesis of membrane sterols such as ergosterol (in fungi), cholesterol (in animals), and phytosterols (in plants). Inhibition of its activity by azole antifungals disrupts membrane integrity, leading to cell death. The enzyme’s mechanism involves oxidative removal of the 14alpha-methyl group from sterol precursors in a three-step reaction. CYP51 is membrane-associated and plays fundamental roles in cellular viability; genetic or pharmacological inhibition is invariably lethal in most organisms that rely on sterol biosynthesis. CYP51 has homologs across kingdoms and can also be targeted for antiparasitic therapy. Resistance to azole antifungals through mutation or upregulation of CYP51 is an emerging clinical challenge, especially in opportunistic fungal pathogens.

Other names

Lanosterol 14-alpha demethylaseCYP51A1 (human isoform)Sterol 14-demethylaseCytochrome P450 51CYP51 family

Azole antifungals (triazoles and imidazoles) inhibit sterol 14alpha-demethylase by binding to the heme iron within the enzyme’s active site, thereby preventing demethylation steps required for ergosterol or cholesterol synthesis in fungi or other organisms. This results in altered membrane composition, loss of membrane integrity, and inhibition of cell growth or death.