Abstract Flavin-dependent halogenases (FHals) catalyse the halogenation of electron-rich substrates, mainly aromatics. Halogenated compounds have many applications, as pharmaceutical, agrochemicals or as starting materials for the synthesis of complex molecules. By exploring the sequenced bacterial diversity, we discovered and characterized XszenFHal, a novel FHal from Xenorhabdus szentirmaii, a symbiotic bacterium of entomopathogenic nematode. The substrate scope of XszenFHal was examined and revealed activities towards tryptophan, indole and indole derivatives, leading to the formation of the corresponding 5-chloro products. XszenFHal makes a valuable addition to the panel of flavin-dependent halogenases already discovered and enriches the potential for biotechnology applications by allowing access to 5-halogenated indole derivatives.
