Biosynthesis of indole-3-acetic acid in Azospirillum brasilense. Insights from quantum chemistry.

Quantum chemical methods AM1 and PM3 and chromatographic methods were used to qualitatively characterize pathways of bacterial production of indole-3-acetic acid (IAA). The standard free energy changes (delta G(o)'sum) for the synthesis of tryptophan (Trp) from chorismic acid via anthranilic acid and indole were calculated, as were those for several possible pathways for the synthesis of IAA from Trp, namely via indole-3-acetamide (IAM), indole-3-pyruvic acid (IPyA), and indole-3-acetonitrile (IAN). The delta G(o)'sum for Trp synthesis from chorismic acid was -402 (-434) kJ.