Coordinates and prevents auxin (IAA) and ethylene biosynthesis, thus regulating auxin homeostasis in young seedlings (PubMed:23377040, PubMed:26163189). Shows aminotransferase activity with methionine; can use the ethylene biosynthetic intermediate L-methionine (L-Met) as an amino donor and the auxin biosynthetic intermediate, indole-3-pyruvic acid (3-IPA) as an amino acceptor to produce L-tryptophan (L-Trp) and 2-oxo-4-methylthiobutyric acid (KMBA) (PubMed:23377040). Can also use tryptophan (Trp), phenylalanine (Phe), and tyrosine (Tyr) as substrates. Regulates tryptophan (Trp) homeostasis and catabolism in mature plants. Also possibly involved in the metabolism of other aromatic amino acids and phenylpropanoid homeostasis (PubMed:26163189). a 2-oxocarboxylate + L-methionine = 4-methylsulfanyl-2-oxobutanoate + an L-alpha-amino acid 2-oxoglutarate + L-tryptophan = indole-3-pyruvate + L-glutamate 2-oxoglutarate + L-tyrosine = 3-(4-hydroxyphenyl)pyruvate + L-glutamate kcat is 2.5 min(-1) with indole-3-pyruvic acid as substrate. kcat is 1.9 min(-1) with L-Met as substrate. kcat is 3.16 min(-1) with L-Phe as substrate (at pH 8.5 and 37 degrees Celsius). Homodimer. Expressed in roots, cotyledons and flowers. Suppressor of sav3 mutant plants leading to rescued hypocotyl elongation in response to shade and restored auxin biosynthetic pathway. In continuous white light, elongated hypocotyls and petioles, with increased leaf hyponasty, decreased leaf area, and accelerated leaf senescence as well as early flowering. Increases levels of auxin (IAA), indole-3-pyruvic acid (3-IPA) and the ethylene precursor 1-aminocyclopropane-1-carboxylate (ACC) (PubMed:23377040). Indole-dependent auxin (IAA) overproduction phenotypes including leaf epinasty and adventitious rooting. In contrast to normal plants, uses primarily Trp-independent (Trp-I) IAA synthesis when grown on indole-supplemented medium, but uses primarily Trp-dependent (Trp-D) IAA synthesis when grown on unsupplemented medium. Accumulates strongly IAA and Trp when grown on indole, probably due to loss of Trp catabolism. Altered phenylpropanoid profile (PubMed:26163189). Belongs to the class-I pyridoxal-phosphate-dependent aminotransferase family.