Molecular cloning and catalytic activity of a membrane-bound prenyl diphosphate phosphatase from Croton stellatopilosus Ohba.

Geranylgeraniol (GGOH), a bioactive acyclic diterpene with apoptotic induction activity, is the immediate precursor of the commercial anti-peptic, plaunotol (18-hydroxy geranylgeraniol), which is found in Croton stellatopilosus (Ohba). From this plant, a cDNA encoding a prenyl diphosphate phosphatase (CsPDP), which catalyses the dephosphorylation of geranylgeranyl diphosphate (GGPP) to GGOH, was isolated using a PCR approach. The full-length cDNA contained 888bp and encoded a 33.6 kDa protein (295 amino acids) that was phylogenetically grouped into the phosphatidic acid phosphatase (PAP) enzyme family. The deduced amino acid sequence showed 6 hydrophobic transmembrane regions with 57-85% homology to the sequences of other plant PAPs. The recombinant CsPDP and its 4 truncated constructs exhibited decreasing dephosphorylation activities relative to the lengths of the N-terminal deletions. While the full-length CsPDP successfully performed the two sequential monodephosphorylation steps on GGPP to form GGOH, the larger N-terminal deletion in the truncated enzymes appeared to specifically decrease the catalytic efficiency of the second monodephosphorylation step. The information presented here on the CsPDP cDNA and factors affecting the dephosphorylation activity of its recombinant protein may eventually lead to the discovery of the specific GGPP phosphatase gene and enzyme that are involved in the formation of GGOH in the biosynthetic pathway of plaunotol in C. stellatopilosus.