Figure 1.

Schematic diagram illustrating the construction of the campesterol and 24-methylene-cholesterol biosynthesis pathways, based on the native ergosterol biosynthesis pathway in Saccharomyces cerevisiae. The campesterol biosynthesis pathway was constructed by disrupting ERG5 and expressing the heterologous 7-dehydrocholesterol reductase gene (DHCR7). The 24-methylene-cholesterol biosynthetic pathway was constructed from the campesterol biosynthesis pathway via the disruption of ERG4. Sterol biosynthesis uses a common acetyl-CoA precursor.