Multifunctional enzyme involved in the biosynthesis of the indole-derived phytoalexin camalexin. Catalyzes two reactions, the formation of dihydrocamalexate from indole-3-acetonitrile-cysteine conjugate and the oxidative decarboxylation of dihydrocamalexate which is the final step in camalexin biosynthesis. Required for the resistance to the fungal pathogens A.brassicicola, B.cinerea, B.elliptica, B.tulipae, L.maculans and Colletotrichum higginsianum. Seems not to be required for resistance to P.syringae, P.porri, and not involved in age-related resistance. 2-(L-cystein-S-yl)-2-(1H-indol-3-yl)-acetonitrile + 2 O2 + 2 reduced [NADPH--hemoprotein reductase] = camalexin + CO2 + 2 H(+) + 4 H2O + hydrogen cyanide + 2 oxidized [NADPH--hemoprotein reductase] By salicylic acid, flagellin, oligogalacturonides, silver nitrate, UV-C and infection with A.alternata and various strains of P.syringae. Activated by the transcription factor WRKY33 upon infection with P.syringae. No visible phenotype under normal growth conditions, but deficient in the phytoalexin camalexin accumulation upon bacterial infection and markedly increased susceptibility to infection by the necrotrophic fungus Alternaria brassicicola. Belongs to the cytochrome P450 family.