Lanosterol is a tetracyclic triterpenoid, which is the compound from which all steroids are derived. Lanosterol synthase is an oxidosqualene cyclase[disambiguation needed] (OSC) enzyme that converts (S)-2,3-oxidosqualene ((S)-2,3-epoxysqualene) to a protosterol cation and finally to lanosterol. Lanosterol is a key four-ringed intermediate in cholesterol biosynthesis. In humans, lanosterol synthase is encoded by the LSS gene. In eukaryotes, lanosterol synthase is an integral monotopic protein associated with the cytosolic side of the endoplasmic reticulum. Some evidence suggests that the enzyme is a soluble (non-membrane bound) protein in the few prokaryotes that produce it. Due to the enzyme’s role in cholesterol biosynthesis, there is interest in lanosterol synthase inhibitors as potential cholesterol reducing drugs, to complement existing statins.
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