Tryptophan-dependent indole-3-acetic acid biosynthesis by 'IAA-synthase' proceeds via indole-3-acetamide

To analyze the conversion of l-tryptophan (l-trp) to indole-3-acetic acid (IAA) in vitro, isotope labeling and GC-MS/MS techniques were used. Cell free protein extracts convert l-trp to IAA via the intermediate indole-3-acetamide, which has earlier been shown to be endogenous to Arabidopsis thaliana.