TERPENOID BIOSYNTHESIS FROM 1-DEOXY-D-XYLULOSE IN HIGHER-PLANTS BY INTRAMOLECULAR SKELETAL REARRANGEMENT

The incorporation of [1-C-13]- and [2,3,4,5-C-13(4)]1-deoxy-D-xylulose into beta-carotene, lutein, phytol, and sitosterol in a cell culture of Catharanthus roseus was analyzed by NMR spectroscopy, The labeling patterns of the isoprene precursors, isopentenyl pyrophosphate and dim ethylallyl pyrophosphate, were obtained from the terpenes by a retrobi osynthetic approach. C-13 Enrichment and (CC)-C-13-C-13 coupling patte rns showed conclusively that 1-deoxy-D-xylulose and not mevalonate is the predominant isoprenoid precursor of phytol, beta-carotene, and lut ein. Label from 1-deoxyxylulose was also diverted to phytosterols to a minor extent (6% relative to carotene and phytol formation). The data demonstrate that the formation of isopentenyl pyrophosphate from pent ulose occurs strictly by an intramolecular rearrangement process.