title: The cyclic keto-enol insecticide spirotetramat inhibits insect and spider mite acetyl-CoA carboxylases by interfering with the carboxyltransferase partial reaction.
abstract: Acetyl-CoA carboxylase (ACC) catalyzes the committed and rate-limiting step in fatty acid biosynthesis. The two partial reactions, carboxylation of biotin followed by carboxyl transfer to the acceptor acetyl-CoA, are performed by two separate domains in animal ACCs. The cyclic keto-enol insecticides and acaricides have been proposed to inhibit insect ACCs. In this communication, we show that the enol derivative of the cylic keto-enol insecticide spirotetramat inhibited ACCs partially purified from the insect species Myzus persicae and Spodoptera frugiperda, as well as the spider mite (Tetranychus urticae) ACC which was expressed in insect cells using a recombinant baculovirus. Steady-state kinetic analysis revealed competitive inhibition with respect to the carboxyl acceptor, acetyl-CoA, indicating that spirotetramat-enol bound to the carboxyltransferase domain of ACC. Interestingly, inhibition with respect to the biotin carboxylase substrate ATP was uncompetitive. Amino acid residues in the carboxyltransferase domains of plant ACCs are important for binding of established herbicidal inhibitors. Mutating the spider mite ACC at the homologous positions, for example L1736 to either isoleucine or alanine, and A1739 to either valine or serine, did not affect the inhibition of the spider mite ACC by spirotetramat-enol. These results indicated different binding modes of the keto-enols and the herbicidal chemical families.
authors.affiliation: BayerCropScience AG, 40789 Monheim, Germany. Electronic address: peter.luemmen@bayer.com.
authors.forename: Peter
authors.initials: P
authors.lastname: Lümmen
authors.affiliation: Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
authors.forename: Jahangir
authors.initials: J
authors.lastname: Khajehali
authors.affiliation: BayerCropScience AG, 40789 Monheim, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Luther
authors.affiliation: Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium; Institute for Biodiversity and Ecosystems Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Leeuwen
mesh_terms: D056810:Acaricides / Q000494:pharmacology; D000103:Acetyl-CoA Carboxylase / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001042:Aphids / Q000187:drug effects* / Q000201:enzymology; D001372:Aza Compounds / Q000494:pharmacology*; D016367:Baculoviridae / Q000235:genetics; D019731:Carbon-Nitrogen Ligases / Q000037:antagonists & inhibitors; D019878:Carboxyl and Carbamoyl Transferases / Q000037:antagonists & inhibitors*; D004274:DNA, Recombinant; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007306:Insecticides / Q000494:pharmacology*; D007700:Kinetics; D013141:Spiro Compounds / Q000494:pharmacology*; D018411:Spodoptera / Q000187:drug effects* / Q000201:enzymology; D040102:Tetranychidae / Q000187:drug effects* / Q000201:enzymology
chemical_list: D056810:Acaricides; D001372:Aza Compounds; D004274:DNA, Recombinant; D004791:Enzyme Inhibitors; D007306:Insecticides; D013141:Spiro Compounds; C570705:spirotetramat; D019878:Carboxyl and Carbamoyl Transferases; D019731:Carbon-Nitrogen Ligases; C019791:biotin carboxylase; D000103:Acetyl-CoA Carboxylase
keywords: Acetyl-CoA carboxylase; Carboxyltransferase; Competitive inhibition; Insecticide; Mode of action; Mutagenesis; Spider mite; Spirotetramat-enol