Squalene synthetase Activators

Squalene synthetase (also known as farnesyl-diphosphate farnesyltransferase) is an enzyme that catalyzes the first step in the biosynthesis of sterols from isoprenoid precursors. It converts two molecules of farnesyl pyrophosphate into squalene. Direct activators in the form of small chemical compounds for squalene synthetase are not commonly reported, as typically the regulation of this enzyme is mediated by feedback mechanisms from downstream sterol products or by protein interactions and post-translational modifications. Squalene synthase is an integral membrane protein located in the endoplasmic reticulum (ER). The enzyme has a unique structure that allows it to bind to two molecules of FPP and facilitate their condensation. The active site contains binding pockets for FPP and NADPH and the catalytic residues that facilitate the reaction.

The compensatory upregulation of squalene synthase can also occur with the use of statins like Simvastatin, which inhibit HMG-CoA reductase, thereby leading to enhanced activity of squalene synthase due to increased transcription and translation of the enzyme. Geranylgeranyl pyrophosphate, an FPP derivative, can feedback inhibit its own synthesis, potentially causing an accumulation of FPP and thus enhancing squalene synthase activity. Additionally, compounds that mimic the substrate or byproducts of the squalene synthase reaction, such as Digeranyl bisphosphonate and Pyrophosphate, can at certain concentrations enhance the enzyme's activity by stabilizing the enzyme-substrate complex or driving the reaction forward through mass action, respectively. This enzyme catalyzes the first step in the pathway that is committed to cholesterol production, merging two FPP molecules in a two-step reaction. Two molecules of FPP are condensed into presqualene pyrophosphate (PSPP). PSPP is then reduced to squalene by NADPH.