Figure 5. Molecular structures of tested chemicals and decarboxylation activity of drDDC WT and three mutants towards different aromatic amino acid substrates.

A, Molecular structures of tyr (tyrosine), o-tyr, m-tyr, DOPA, trp (tryptophan) and 5-HTP; B, Decarboxylation activity. A typical reaction mixture of 100 µl consists of 5 µg of purified drDDC WT or any mutants, 1 mM of DOPA, 5-HTP, m-tyr, o-tyr, trp, tyr or d-DOPA, and 40 mM PLP in 150 mM potassium phosphate buffer, pH 7.0. Vertical axis shows the specific activity of the enzymes to each substrate (trp, tyr, and d-DOPA are not shown because none of the proteins showed any activity to them), and horizontal axis shows the drDDC WT and mutant protein names.