ergoszterol

Ergosterol is a sterol that constitutes the principal membrane sterol in most fungi and yeasts, functioning analogously to cholesterol in animal cells. It helps regulate membrane fluidity and permeability and supports the activity of membrane-bound proteins. Because fungi rely on ergosterol, it serves as a key biochemical marker of fungal membranes in research and industry.

Biosynthesis of ergosterol occurs via the mevalonate pathway, leading to the formation of squalene and oxidosqualene, then lanosterol, and finally ergosterol through multiple enzymatic steps. A distinctive feature of ergosterol is the presence of additional double bonds and methyl substitutions compared with cholesterol. The C-14-demethylation step is a crucial point in the pathway and is a common target of antifungal drugs such as azoles; inhibition of ergosterol synthesis disrupts fungal membrane integrity.

In addition to its structural role, ergosterol is a precursor to vitamin D2 (ergocalciferol) when exposed to ultraviolet light. Its presence is used in environmental and clinical studies as a biomarker to estimate fungal biomass, due to its relative specificity for fungi compared with plant and animal sterols.

Ergosterol is not produced by animals or higher plants, which instead contain cholesterol and various phytosterols, respectively. It is widely present in fungi, including yeasts and molds, and is a central target in antifungal pharmacology and a useful analytical target in fungal ecology and microbiology.