title: New cyclization mechanism for squalene: a ring-expansion step for the five-membered C-ring intermediate in hopene biosynthesis.
abstract: Three triterpenes having the 6/6/5-fused tri- and 6/6/6/5-fused tetracyclic skeletons were isolated from an incubation mixture of the mutated F601A enzyme, these products being in accordance with a Markovnikov closure. Successful trapping of the tricyclic cationic intermediate by using the squalene analog having a highly nucleophilic hydroxyl group leads us to propose that the ring expansion process of the 5-membered C-ring is involved in the squalene cyclization cascade.
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Japan. hoshitsu@agr.niigata-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Hoshino
authors.forename: M
authors.initials: M
authors.lastname: Kouda
authors.forename: T
authors.initials: T
authors.lastname: Abe
authors.forename: S
authors.initials: S
authors.lastname: Ohashi
mesh_terms: D019943:Amino Acid Substitution; D019751:Intramolecular Transferases / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000378:metabolism; D013185:Squalene / Q000737:chemistry* / Q000378:metabolism; D014315:Triterpenes / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D014315:Triterpenes; C028765:diploptene; D013185:Squalene; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase