Activities of TDC1, TDC2, TDC3, and TDC variants mutated in the region of the PLP-binding active site. Panel (A) shows the activity of wild-type (wt) TDC1 and TDC2 (black bars) and their respective Cys/Ser PLP-site mutants (grey bars) measured as tryptamine production in yeast extracts [indicated are means and error bars show the standard deviation (std dev); n = 2]. Panel (B) shows the accumulation of tryptamine in yeast cultures transformed with the wild-type (wt) genes TDC1, TDC2, and TDC3, and mutant variants of TDC1 and TDC2. Data are representative of two separate experiments and were normalized to the median of all measurements; shown are the means from two biological replicates (=independent transformants), measured in duplicate. Error bars indicate std. dev.