http://cfs.nrcan.gc.ca/authors/read/21042?lang=en_CA Publications by R. Brasseur en-ca 2009-11-10 00:00:00 MST 2009-11-10 00:00:00 MST webmaster@nofc.cfs.nrcan.gc.ca http://cfs.nrcan.gc.ca/publications?id=30291 In addition to providing lipid chains for protein prenylation, short-chain isoprenyl diphosphate synthases (scIPPSs) play a pivotal role in the biosynthesis of numerous mevalonate pathway end-products, including insect juvenile hormone and terpenoid pheromones. For this reason, they are being considered as targets for pesticide development. Recently, we characterized an aphid scIPPS displaying dual geranyl diphosphate (GPP; C₁₀)/farnesyl diphosphate (FPP; C₁₅) synthase activity <em>in vitro</em>. To identify the mechanism(s) responsible for this dual activity, we assessed the product selectivity of aphid scIPPSs bearing mutations at Gln107 and/or Leu110, the fourth and first residue upstream from the "first aspartate-rich motif" (FARM), respectively. All but one resulted in significant changes in product chain-length selectivity, effectively increasing the production of either GPP (Q107E, L110W) or FPP (Q107F, Q107F–L110A); the other mutation (L110A) abolished activity. Although some of these effects could be attributed to changes in steric hindrance within the catalytic cavity, molecular dynamics simulations identified other contributing factors, including residue-ligand Van der Waals interactions and the formation of hydrogen bonds or salt bridges between Gln107 and other residues across the catalytic cavity, which constitutes a novel product chain-length determination mechanism for scIPPSs. Thus the aphid enzyme apparently evolved to maintain the capacity to produce both GPP and FPP through a balance between these mechanisms. Tue, 10 Nov 2009 http://cfs.nrcan.gc.ca/publications?id=30291 http://cfs.nrcan.gc.ca/publications?id=28598 We report on the cDNA cloning and characterization of a novel short-chain isoprenyl diphosphate synthase from the aphid <em>Myzus persicae</em>. Of the three IPPS cDNAs we cloned, two yielded prenyltransferase activity following expression in <em>Escherichia coli</em>; these cDNAs encode identical proteins except for the presence, in one of them, of an N-terminal mitochondrial targeting peptide. Although the aphid enzyme was predicted to be a farnesyl diphosphate synthase by BLASTP analysis, rMpIPPS, when isopentenyl diphosphate and dimethylallyl diphosphate are supplied as substrates, typically generated geranyl diphosphate (C10) as its main product, along with significant quantities of farnesyl diphosphate (C15). Analysis of an MpIPPS homology model pointed to substitutions that could confer GPP/FPP synthase activity to the aphid enzyme. Tue, 03 Jun 2008 http://cfs.nrcan.gc.ca/publications?id=28598