Detection of an indole oxidizing system in maize leaves

An enzyme activity which brings about a rapid indole disappearance has been detected in cell free extracts of maize ($\text{Zea}\text{mays}$ L.) leaves. The indole utilization by this enzyme system is not dependent on L-serine and pyridoxal phosphate. It does not result in incorporation of (5-³H) indole or (1-¹⁴C) serine into tryptophan. There was no net tryptophan synthesis concomittant with indole disappearance. The enzyme activity is strongly inhibited by dithionite and diethyl-dithiocarbamate. The inhibition by the latter could be specifically removed by Cu²⁺. The activity of dialyzed enzyme could be restored by addition of Cu²⁺ and FAD. The products of indole oxidation were characterized as anthranilic acid and anthranil (2,1-benzisooxazole). The activity of the indole oxidizing system was 2 to 3 times higher in normal maize varieties (Ganga-2 and Ganga-5) than in Opaque-2.