Involved in the biosynthesis of the antifungal antibiotic pyrrolnitrin. Catalyzes the ring rearrangement and decarboxylation to convert 7-chloro-L-tryptophan (7-CLT) to monodechloroaminopyrrolnitrin (MDA). It can also use 7-chloro-D-tryptophan, but 7-chloro-L-tryptophan is the preferred natural enantiomer. 7-chloro-L-tryptophan + AH2 + O2 = A + CO2 + 2 H2O + monodechloroaminopyrrolnitrin Antibiotic biosynthesis. Monomer. Cells lacking this gene lose the ability to produce pyrrolnitrin. Belongs to the PrnB family.