Figure 4.

In vitro assay of IAA-amido synthetase activity. The indicated IAA-amino acid conjugate species in individual reactions catalyzed by TLD1 (A–E) or TLD2 (F) recombinant protein were detected by HPLC-ESI-MS/MS at different MRM spectra (for optimal parameters for the MRM, see Supplemental Table S1; for details of the biochemical reaction, see “Materials and Methods”). Conjugated IAA (black peaks) and free IAA (gray peaks) intensities are shown in arbitrary units. In F, no IAA-Glu peak was observed when TLD1 in E was replaced by TLD2.