Fig. 4. Characterization of all products in the AetD-catalysed reaction.

a, Schematic showing the product distribution of the AetD-catalysed reaction in native and shunt pathways. The native pathway yields 5,7-dibromo-indole-3-carbonitrile (8) and glycolic acid (11) as products, whereas 5,7-dibromo-indole-3-carbaldehyde (10), glyoxylic acid (12) and ammonia are the products in the shunt pathway. Labelling experiments with ¹³C-labelled isotopologues of the substrate confirmed the fate of the carbon atoms of the 2-aminopropionyl side chain and are colour-coded accordingly. Refer to Extended Data Figs. 5, 7 and 8, and Supplementary Fig. 4 for full set of liquid chromatograms, and MS and NMR spectra. b, Liquid chromatogram showing the formation of shunt product 10 in addition to native product 8 in the AetD full reaction assay. c, ¹³C NMR spectrum of the AetD-catalysed reaction in the presence of [2-¹³C]-5,7-dibromo-l-tryptophan (7). In the full reaction assay, the C2 peak corresponding to substrate 7 disappeared, whereas two new ¹³C peaks appeared, which we characterized as the alcohol and aldehyde carbons of 11 and 12, respectively. Asterisks represent glycerol peaks from the AetD protein stock.