ABSTRACT
The biosynthetic origin of isopentenyl diphosphate in the polyisoprenoid biosynthesis of the rubber-producing plant Eucommia ulmoides Oliver was elucidated for the first time by feeding experiments using 13C-labeled isotopomers of (RS)-mevalonate, 1-deoxy-D-xylulose-3,4,5-triacetate, 2C-methyl-D-erythritol-1,2,3,4-tetraacetate, and pyruvate. After 13C-labeled isotopomers were fed to the young seedlings, the polyisoprenoid fractions were prepared and analyzed by 13C NMR. The NMR data showed that the isoprene units of polyisoprenoid derived from isopentenyl diphosphate, which was biosynthesized using both mevalonate and 1-deoxy-D-xylulose-5-phosphate in E. ulmoides. It is assumed that the cross-talk of isopentenyl diphosphate, derived from both pathways, occurs during the biosynthesis of polyisoprenoid; therefore, it was observed in the formation of low-molecular weight isoprenoids.
Subject(s)
Eucommiaceae/metabolism , Mevalonic Acid/metabolism , Polyisoprenyl Phosphates/metabolism , Rubber/chemical synthesis , Carbon Isotopes , Magnetic Resonance Spectroscopy , Polyisoprenyl Phosphates/biosynthesis , Polyisoprenyl Phosphates/isolation & purification , Seedlings/metabolism , SolventsABSTRACT
Natural rubber is synthesized as rubber particles in the latex, the fluid cytoplasm of laticifers, of Hevea brasiliensis. Although it has been found that natural rubber is biosynthesized through the mevalonate pathway, the involvement of an alternative 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is uncertain. We obtained all series of the MEP pathway candidate genes by analyzing expressed sequence tag (EST) information and degenerate PCR in H. brasiliensis. Complementation experiments with Escherichia coli mutants were performed to confirm the functions of the MEP pathway gene products of H. brasiliensis together with those of Arabidopsis thaliana, and it was found that 1-deoxy-D-xylulose-5-phosphate reductoisomerase, 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase, and 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase of H. brasiliensis were functionally active in the E. coli mutants. Gene expression analysis revealed that the expression level of the HbDXS2 gene in latex was relatively high as compared to those of other MEP pathway genes. However, a feeding experiment with [1-(13)C] 1-deoxy-D-xylulose triacetate, an intermediate derivative of the MEP pathway, indicated that the MEP pathway is not involved in rubber biosynthesis, but is involved in carotenoids biosynthesis in H. brasiliensis.
Subject(s)
Erythritol/analogs & derivatives , Euphorbiaceae/genetics , Euphorbiaceae/metabolism , Genes, Plant/genetics , Hevea/genetics , Rubber/metabolism , Sugar Phosphates/metabolism , Amino Acid Sequence , Carbon Isotopes , Cloning, Molecular , Databases, Genetic , Erythritol/metabolism , Expressed Sequence Tags , Gene Expression Regulation, Plant , Hevea/metabolism , Molecular Sequence Data , Mutation , Phylogeny , Polymerase Chain Reaction , Seedlings/genetics , Seedlings/metabolism , Staining and Labeling , Xylulose/analogs & derivatives , Xylulose/metabolismABSTRACT
The antitumor activity of newly developed taxoids possessing a sugar moiety (glucose, galactose or mannose) to improve water solubility was evaluated. Galactose-bound taxoid (10-alpha-GAG-DT) proved superior to all other taxoids in both water solubility and antitumor activity. Therapeutic efficacy of 10-alpha-GAG-DT in terms of in vivo antitumor activity was found to be approximately equivalent to that of docetaxel, which is known to be superior to that of paclitaxel. The observation that the sugar moiety was gradually hydrolyzed in serum to release docetaxel indicates that 10-alpha-GAG-DT acts as a prodrug.
Subject(s)
Antineoplastic Agents, Phytogenic , Taxoids/pharmacology , Animals , Body Weight/drug effects , Chemical Phenomena , Chemistry, Physical , Docetaxel , Drug Screening Assays, Antitumor , Humans , Indicators and Reagents , Leukemia P388/drug therapy , Male , Mice , Solubility , Taxoids/chemistry , WaterABSTRACT
Feeding experiments were independently performed with [1-13C]deoxy-D-xylulose triacetate and (RS)-[2-13C]mevalonolactone in the tobacco plant. The labeling pattern for solanesol was elucidated to reveal that the isoprene moiety of solanesol would be derived from deoxy-xylulose. The result strongly suggests that tobacco solanesol is biosynthesized via the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway.
