5-Methyltryptophan resistant cells of Catharanthus roseus

Several cell lines resistant to 5-methyltryptophan were selected from wild type cells of different Catharanthus roseus suspension cultures. The resistant cells had up to 30 times the normal levels of free tryptophan. Despite the increased pool size of tryptophan anthranilate synthetase activity of resistant cells was as sensitive to inhibition by L-tryptophan as wild type cells. The overproduction of tryptophan did not lead to intensified accumulation of tryptamine nor of indole alkaloids. This was supported by a low conversion of tryptophan to tryptamine in vivo and in vitro. The overproduction of one of the primary precursors was evidently not sufficient to stimulate the rate of indole alkaloid synthesis in Catharanthus cells.