Biooxidation of indole and characteristics of the responsible enzymes

Indole, an electron-rich N-aromatic heterocyclic organic compound, functions as a popular component of fragrances, indicator of some diseases and signal molecule in plant, animal and microorganism, respectively. It also serves as the precursor, core building block and functional group of many important biochemical molecules and compounds, such as plant hormones, alkaloids, indigoids, certain proteins and enzymes. Most of these important molecules and compounds if not all, are originated, fully or partly, from biooxidation of indole. This review outlined the progress in the study of biooxidation of indole and responsible enzymes in microorganism and in plant in past two decades, summarized the pathways of indole biooxidation with an emphasis on those leading to formation of indigo and indirubin in plant and discussed the perspectives of the research in indole biooxidation with a focus on the application of indole and its derivatives in agrochemicals, pharmaceuticals and environmental pollution remedy.