Involved in the biosynthesis of ambiguines, a family of hapalindole-type alkaloids (PubMed:24180436). Responsible for the synthesis of Z-3-(2-isocyanoethen)-indole, a biosynthetic precursor to all ambiguines (PubMed:24180436, PubMed:28212039). (2S)-3-(1H-indol-3-yl)-2-isocyanopropanoate + 2-oxoglutarate + H(+) + O2 = 3-[(Z)-2-isocyanoethenyl]-1H-indole + 2 CO2 + H2O + succinate Binds 1 Fe(2+) per subunit. Belongs to the TfdA dioxygenase family.