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Lanosterol synthase (EC 5.4.99.7) is an oxidosqualene cyclase (OSC) enzyme that converts -2,3-oxidosqualene to a protosterol cation and finally to lanosterol. [5] Lanosterol is a key four-ringed intermediate in cholesterol biosynthesis.
Lanosterol is a tetracyclic triterpenoid and is the compound from which all animal and fungal steroids are derived. By contrast, plant steroids are produced via cycloartenol . [ 1 ] In the eyes of vertebrates, lanosterol is a natural constituent, having a role in maintaining health of the lens .
Overview of cholesterol biosynthesis. Lanosterol is a precursor to cholesterol. This final conversion occurs in many steps. Mechanistically, the enzyme oxidosqualene:lanosterol cyclase catalyzes the formation of four rings along the long chain of the substrate (oxidosqualene), producing lanosterol.
2,3-Oxidosqualene is the substrate of various oxidosqualene cyclases, including lanosterol synthase, which produces lanosterol, a precursor to cholesterol. [1] The stereoisomer (R)-2,3-oxidosqualene is an inhibitor of lanosterol synthase.
Ergosterol is a smaller molecule than lanosterol; it is synthesized by combining two molecules of farnesyl pyrophosphate, a 15-carbon-long terpenoid, into lanosterol, which has 30 carbons. Then, two methyl groups are removed, making ergosterol.
7-DHC is used for vitamin D3 synthesis via lanosterol in land animals, via cycloartenol in plants, and in algae together with another provitamin D ergosterol for D2. In fungi solely ergosterol is used for synthesis of D2 via lanosterol. [15]
Lanosterol 14α-demethylase (CYP51A1) is the animal version of a cytochrome P450 enzyme that is involved in the conversion of lanosterol to 4,4-dimethylcholesta-8(9),14,24-trien-3β-ol. [5] The cytochrome P450 isoenzymes are a conserved group of proteins that serve as key players in the metabolism of organic substances and the biosynthesis of ...
De novo synthesis, both in astrocytes and hepatocytes, occurs by a complex 37-step process. This begins with the mevalonate or HMG-CoA reductase pathway, the target of statin drugs, which encompasses the first 18 steps. This is followed by 19 additional steps to convert the resulting lanosterol into cholesterol. [13]