title: Further Insight into Polycyclization Cascades of Acyclic Geranylfarnesol and its Acetate by Squalene-hopene Cyclase from Alicyclobacillus acidocaldarius.
abstract: The enzymatic reactions of geranylfarnesol (8) and its acetate 9, classified as sesterterpenes (C25), using squalene-hopene cyclase (SHC) were investigated. The enzymatic reaction of 8 afforded 6/6-fused bicyclic 20, 6/6/6-fused tricyclic 21, and 6/6/6/6-fused tetracyclic compounds 22 and 23 as the main products (35% yield), whereas that of 9 afforded two 6/6/6-fused tricyclic compounds 24 and 25 in a high yield (76.3%) and a small amount (5.0%) of 26 (the acetate of 22). A significantly higher conversion of 9 indicates that the arrangement of the substrate in the reaction cavity changed. The lipophilic nature and/or the bulkiness of the acetyl group may have changed its binding with SHC, thus placing the terminal double bond of 9 in the vicinity of the DXDD motif of SHC, which is responsible for the proton attack on the double bond to initiate the polycyclization reaction. The results obtained for 8 are different to some extent than those reported by Shinozaki et al. The products obtained in this study were deprotonated compounds; however, the products reported by Shinozaki et al. were hydroxylated compounds.
authors.forename: Jun
authors.initials: J
authors.lastname: Cheng
authors.forename: Chiaki
authors.initials: C
authors.lastname: Nakano
authors.forename: Guang Lu
authors.initials: GL
authors.lastname: Shi
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Hoshino
mesh_terms: D056450:Alicyclobacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D005778:Gefarnate / Q000031:analogs & derivatives* / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D019751:Intramolecular Transferases / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure
chemical_list: D001426:Bacterial Proteins; D005778:Gefarnate; C043321:geranylfarnesol; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase