Restoration of Serotonin Biosynthesis in Cell Suspension Cultures of Peganum harmala by Selection for 4-methyltryptophan-tolerant Cell Lines

Summary The original capacity of Peganum harmala cell suspension cultures for serotonin biosynthesis which had been lost during 6 years of cultivation, was restored by selection of 4-methyltryptophan-tolerant cell lines. Four cell lines were recovered accumulating 1–2% serotonin of dry mass when maintained on the growth medium, while one tolerant line was not able to form higher levels of serotonin. In contrast to non-producing cell lines the serotonin producing cell lines expressed tryptophan decarboxylase activity, were able to use tryptophan for serotonin biosynthesis, and detoxified 4-methyltryptophan to 4-methyltryptamine. The better ability of the TDC containing cell lines for detoxification of 4-methyltryptophan seems to contribute at least partially to the overall tolerance of the selected cell lines. The original β-carboline alkaloid levels were not restored by this technique. Key words