title: Different reaction mechanisms for cis- and trans-prenyltransferases.
abstract: Octaprenyl diphosphate synthase (OPPs) and undecaprenyl diphosphate synthases (UPPs) catalyze consecutive condensation reactions of farnesyl diphosphate (FPP) with 5 and 8 isopentenyl diphosphate (IPP) to generate C(40) and C(55) products with trans- and cis-double bonds, respectively. In this study, we used IPP analogue, 3-bromo-3-butenyl diphosphate (Br-IPP), in conjunction with radiolabeled FPP, to probe the reaction mechanisms of the two prenyltransferases. Using this alternative substrate with electron-withdrawing bromo group at the C3 position to slow down the condensation step, trapping of farnesol in the OPPs reaction from radiolabeled FPP under basic condition was observed, consistent with a sequential mechanism. In contrast, UPPs reaction yielded no farnesyl carbocation intermediate under the same condition with radiolabeled FPP and Br-IPP, indicating a concerted mechanism. Our data demonstrate the different reaction mechanisms for cis- and tran-prenyltransferases although they share the same substrates.
authors.affiliation: Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, ROC.
authors.forename: Yen-Pin
authors.initials: YP
authors.lastname: Lu
authors.forename: Hun-Ge
authors.initials: HG
authors.lastname: Liu
authors.forename: Po-Huang
authors.initials: PH
authors.lastname: Liang
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry*; D002855:Chromatography, Thin Layer; D011756:Diphosphates / Q000737:chemistry; D045782:Hemiterpenes / Q000737:chemistry*; D010755:Organophosphates; D009943:Organophosphorus Compounds / Q000737:chemistry*; D011106:Polyisoprenyl Phosphates / Q000737:chemistry; D012717:Sesquiterpenes / Q000737:chemistry; D013379:Substrate Specificity; D014166:Transferases / Q000737:chemistry*
chemical_list: C535073:3-bromo-3-butenyl diphosphate; D011756:Diphosphates; D045782:Hemiterpenes; D010755:Organophosphates; D009943:Organophosphorus Compounds; D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; C004809:isopentenyl pyrophosphate; C004808:farnesyl pyrophosphate; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C106821:cis-prenyl transferase; C048987:octaprenyl pyrophosphate synthetase; C023266:undecaprenyl pyrophosphate synthetase