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Updated: Jun 2, 2026

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
Squalene-hopene cyclases.
Gabriele Siedenburg1, Dieter Jendrossek
1Institute for Microbiology, University of Stuttgart, Stuttgart, Germany.
Squalene-hopene cyclases (SHCs) and oxidosqualene cyclases (OSCs) catalyze complex one-step reactions to form essential cyclic triterpenoids like hopanoids and sterols. This study details the mechanism of Alicyclobacillus acidocaldarius SHC.
Area of Science:
- Biochemistry
- Molecular Biology
- Organic Chemistry
Background:
- Hopanoids and sterols are vital cyclic triterpenoids in prokaryotes and eukaryotes.
- Their synthesis involves squalene-hopene cyclase (SHC) or oxidosqualene cyclase (OSC) enzymes.
- SHCs and OSCs share a common ancestor and catalyze complex one-step reactions.
Purpose of the Study:
- To summarize knowledge on triterpene cyclase properties.
- To detail the reaction mechanism of Alicyclobacillus acidocaldarius SHC.
- To include properties of other SHCs.
Main Methods:
- Literature review on triterpene cyclases.
- Analysis of the enzymatic reaction mechanism of Alicyclobacillus acidocaldarius SHC.
- Comparative analysis of SHC properties.
Main Results:
- The SHC reaction is a complex one-step enzymatic process.
- Formation of five rings, 13 covalent bonds, and nine stereocenters.
- Detailed insights into the mechanism of Alicyclobacillus acidocaldarius SHC.
Conclusions:
- Triterpene cyclases are crucial enzymes in synthesizing hopanoids and sterols.
- The reaction mechanism of SHC is highly complex.
- Further understanding of SHC properties is essential.
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