Tryptamine production in S. cerevisiae cultures expressing TDC genes from black cohosh. Panel (A) shows mass chromatograms of supernatants from galactose-induced 24-h cultures of yeast cells transformed with TDC1, TDC2, or TDCK314R in the pYES2 vector; cultures of yeast cells transformed with the vector only were used as a negative control. Panel (B) shows mass spectra extracted from the peaks boxed in grey in panel (A). A peak eluting at ~2.47 min, indicating a compound with a mass within 20 ppm of the expected mass of 161.1079 (in ES+ mode) for tryptamine, is present in the authentic tryptamine standard as well as in TDC1- and TDC2-expressing cultures, but not in TDCK314R (in which the L-lysine residue for PLP binding was replaced with L-arginine) or the vector-only control. Panel (C) shows the normalized concentration of tryptamine estimated from the values for total ion current (TIC) of its mass peak in Gal-induced yeast cultures transformed with TDC1, TDC2, or TDC3 (shown are means from two independent experiments; error bars indicate std dev).