ISOPENTENYL DIPHOSPHATE ISOMERASE AND PRENYLTRANSFERASE ACTIVITIES INRUBIACEOUS AND APOCYNACEOUS CULTURES

Isopentenyl diphosphate (IPP) isomerase (EC 5;3.3.2) and farnesyl diph osphate (FPP) synthase (EC 2.5.1.10) activities were studied in plant cell cultures of Cinchona robusta, Morinda citrifolia, Rubia tinctorum , all belonging to the Rubiaceae, and Tabernaemontana divaricata and C atharanthus roseus, both belonging to the Apocynaceae. The presence of isoforms of IPP isomerase was detected after hydroxyapatite chromatog raphy and by Western blotting using anti-IPP isomerase antibodies. The Rubiaceae cultures are able to accumulate anthraquinones, and for the ir biosynthesis isoprene C-5-units are required. In a M. citrifolia ce ll line accumulating anthraquinones (AQ +), an almost two-fold higher IPP isomerase was observed compared with a cell line without accumulat ion of anthraquinones. In the Western blots three polypeptides were de tected in the extracts from the AQ + cells. In C. robusta cells the an thraquinone biosynthesis was induced by medium optimization and by eli citation. After both treatments, a specific isoform of IPP isomerase w as induced. The C. roseus culture (not accumulating anthraquinones) ex pressed relatively low IPP isomerase activity, but two isoforms could be detected. The enzyme activities as observed in the different Rubiac eae cultures may indicate an efficient channelling of C-5-units into a nthraquinone biosynthesis. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.