title: Inhibition of monoterpene cyclases by inert analogues of geranyl diphosphate and linalyl diphosphate.
abstract: The tightly coupled nature of the reaction sequence catalyzed by monoterpene synthases has prevented direct observation of the topologically required isomerization step leading from geranyl diphosphate to the enzyme-bound, tertiary allylic intermediate linalyl diphosphate, which then cyclizes to the various monoterpene skeletons. X-ray crystal structures of these enzymes complexed with suitable analogues of the substrate and intermediate could provide a clearer view of this universal, but cryptic, step of monoterpenoid cyclase catalysis. Toward this end, the functionally inert analogues 2-fluorogeranyl diphosphate, (+/-)-2-fluorolinalyl diphosphate, and (3R)- and (3S)-homolinalyl diphosphates (2,6-dimethyl-2-vinyl-5-heptenyl diphosphates) were prepared, and compared to the previously described substrate analogue 3-azageranyl diphosphate (3-aza-2,3-dihydrogeranyl diphosphate) as inhibitors and potential crystallization aids with two representative monoterpenoid cyclases, (-)-limonene synthase and (+)-bornyl diphosphate synthase. Although these enantioselective synthases readily distinguished between (3R)- and (3S)-homolinalyl diphosphates, both of which were more effective inhibitors than was 3-azageranyl diphosphate, the fluorinated analogues proved to be the most potent competitive inhibitors and have recently yielded informative liganded structures with limonene synthase.
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Karp
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Bindu
authors.initials: B
authors.lastname: Santhamma
authors.forename: Bryce
authors.initials: B
authors.lastname: Assink
authors.forename: Robert M
authors.initials: RM
authors.lastname: Coates
authors.forename: Rodney B
authors.initials: RB
authors.lastname: Croteau
mesh_terms: D000080462:Acyclic Monoterpenes; D011756:Diphosphates / Q000737:chemistry*; D004224:Diterpenes / Q000737:chemistry*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000737:chemistry; D004795:Enzyme Stability; D019753:Intramolecular Lyases / Q000037:antagonists & inhibitors*; D039821:Monoterpenes / Q000737:chemistry*; D011106:Polyisoprenyl Phosphates / Q000737:chemistry*
chemical_list: D000080462:Acyclic Monoterpenes; D011756:Diphosphates; D004224:Diterpenes; D004791:Enzyme Inhibitors; D039821:Monoterpenes; D011106:Polyisoprenyl Phosphates; C511282:geranyl diphosphate; C036751:linalyl pyrophosphate; D019753:Intramolecular Lyases; C040265:pinene cyclase I