Sterol 14-demethylase

An enzyme involved in sterol biosynthesis

Overview

Chemical structure of ergosterol, a product of sterol 14-demethylase activity.

Sterol 14-demethylase is an enzyme that plays a crucial role in the biosynthesis of sterols, which are essential components of cell membranes in eukaryotic organisms. This enzyme is part of the cytochrome P450 family and is responsible for the demethylation of lanosterol, a key step in the production of ergosterol in fungi and cholesterol in animals.

Function

Sterol 14-demethylase catalyzes the removal of a 14_-methyl group from lanosterol, converting it into 4,4-dimethylcholesta-8,14,24-trien-3_-ol. This reaction is a critical step in the mevalonate pathway, which is the metabolic pathway that produces sterols. In fungi, the end product of this pathway is ergosterol, while in animals, it leads to the production of cholesterol.

Mechanism

The enzyme functions by utilizing a heme cofactor to facilitate the oxidation of the 14_-methyl group. This process involves three sequential oxidation steps, ultimately resulting in the release of formic acid and the formation of a double bond at the C14 position. The activity of sterol 14-demethylase is dependent on the presence of molecular oxygen and NADPH, which serve as electron donors in the reaction.

Clinical Significance

Ergosterol is a target for antifungal drugs.

Sterol 14-demethylase is a target for antifungal drugs, such as azoles, which inhibit its activity and disrupt the synthesis of ergosterol. This leads to the accumulation of toxic sterol intermediates and compromises the integrity of the fungal cell membrane, ultimately resulting in cell death. The inhibition of this enzyme is a key mechanism of action for many antifungal therapies used to treat infections caused by pathogenic fungi.

Related pages

• Cytochrome P450
• Ergosterol
• Cholesterol
• Mevalonate pathway
• Azole antifungals