Selection of Cell Lines of Catharanthus roseus with Increased Tryptophan Decarboxylase Activity

Catharanthus roseus, Cell Suspension C ultures, T ryp tophan A nalogues, R esistant Cell Lines, Tryptophan Decarboxylase, Indole A lkaloids Cell lines o f Catharanthus roseus were selected for resistance to 4 -m ethyltryptophan (4-M T) in order to get strains with increased activities o f tryp tophan decarboxylase (TD C ). This enzym e may exert a decisive regulatory control in indole alkalo id biosynthesis. 4 -M ethyltryptophan is a substrate for T D C and is detoxified by this enzyme. All 4-M T resistant cell lines show ed increased TDC activity (3-to 10-fold) and h igher accum ulation o f tryp tam ine (3to 5-fold). Two of these cell lines with increased TD C activity accum ulated indole alkaloids in the growth medium, whereas in wild type cultures and o ther resistant cell lines this was not the case. All the cell lines obtained were not only resistant to 4-M T (20to 70-tim es m ore than wild type cells) but were also cross-resistant to o ther tryp tophan analogues w hich are not m etabolized by TDC. Therefore the resistance was not only due to a better de toxification o f the analogue. T he selected cell lines also contained 2 to 6 tim es h igher levels o f L-tryptophan bu t the feedback sensitivity o f the anthranilate synthetase o f the resistant cells was not altered.