Mapping of multiple mouse loci related to the farnesyl pyrophosphate synthetase gene

Cloning and characterization of farnesyl pyrophosphate synthase from the highly branched isoprenoid producing diatom Rhizosolenia setigera

The diatom Rhizosolenia setigera Brightwell produces highly branched isoprenoid (HBI) hydrocarbons that are ubiquitously present in marine environments. The hydrocarbon composition of R. setigera varies between C₂₅ and C₃₀ HBIs depending on the life cycle stage with regard to auxosporulation. To better understand how these hydrocarbons are biosynthesized, we characterized the farnesyl pyrophosphate (FPP) synthase (FPPS) enzyme of R. setigera. An isolated 1465-bp cDNA clone contained an open reading frame spanning 1299-bp encoding a protein with 432 amino acid residues. Expression of the RsFPPS cDNA coding region in Escherichia coli produced a protein that exhibited FPPS activity in vitro. A reduction in HBI content from diatoms treated with an FPPS inhibitor, risedronate, suggested that RsFPPS supplies precursors for HBI biosynthesis. Product analysis by gas chromatography-mass spectrometry also revealed that RsFPPS produced small amounts of the cis-isomers of geranyl pyrophosphate and FPP, candidate precursors for the cis-isomers of HBIs previously characterized. Furthermore, RsFPPS gene expression at various life stages of R. setigera in relation to auxosporulation were also analyzed. Herein, we present data on the possible role of RsFPPS in HBI biosynthesis, and it is to our knowledge the first instance that an FPPS was cloned and characterized from a diatom.

A model for farnesoid feedback control in the mevalonate pathway

Mevalonate is the rate-limiting substrate leading to farnesyl pyrophosphate (FPP), the central intermediate for isoprenoids such as cholesterol, dolichols, ubiquinone, and carotenoids. One major challenge has been to identify the isoprenoid effector molecules and transcription factors mediating negative regulation in this metabolic pathway. A nuclear receptor called FXR has recently been characterized that is activated by farnesyl pyrophosphate metabolites such as farnesol, farnesal, farnesoic acid, and methyl farnesoate. FXR expression in isoprenoidogenic tissues suggests a hypothesis that these intracellular "farnesoids" may be signals for transcriptional feedback control of cholesterol biosynthesis.