title: Squalene-hopene cyclases.
abstract: Hopanoids and sterols are members of a large group of cyclic triterpenoic compounds that have important functions in many prokaryotic and eukaryotic organisms. They are biochemically synthesized from linear precursors (squalene, 2,3-oxidosqualene) in only one enzymatic step that is catalyzed by squalene-hopene cyclase (SHC) or oxidosqualene cyclase (OSC). SHCs and OSCs are related in amino acid sequences and probably are derived from a common ancestor. The SHC reaction requires the formation of five ring structures, 13 covalent bonds, and nine stereo centers and therefore is one of the most complex one-step enzymatic reactions. We summarize the knowledge of the properties of triterpene cyclases and details of the reaction mechanism of Alicyclobacillus acidocaldarius SHC. Properties of other SHCs are included.
authors.affiliation: Institute for Microbiology, University of Stuttgart, Stuttgart, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Siedenburg
authors.forename: Dieter
authors.initials: D
authors.lastname: Jendrossek
mesh_terms: D056450:Alicyclobacillus / Q000201:enzymology*; D019143:Evolution, Molecular; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013185:Squalene / Q000378:metabolism*; D014315:Triterpenes / Q000378:metabolism*
chemical_list: D014315:Triterpenes; C028765:diploptene; D013185:Squalene; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase; C021924:lanosterol synthase