Characterization of a novel aphid prenyltransferase displaying dual geranyl/farnesyl diphosphate synthase activity

We report on the cDNA cloning and characterization
of a novel short-chain isoprenyl diphosphate synthase from the
aphid Myzus persicae. Of the three IPPS cDNAs we cloned,
two yielded prenyltransferase activity following expression in
Escherichia coli; 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.