oxidizing enzyme in Vitis leaves

Ab~t.ract: An indole oxidase from leaves of Vilis vinifera L. was isolated and purified to homogeneity. The punfled enzyme (Mw 65,000) catalysed the conversion of indole into anthranilic acid, with S-methylindole 5-bromoindole and 5-hydroxyindole, also being llsed as subsfrates. Km value for the indole was 0.125 mM. The opti.mum pH for the react.ion was 5.0: The ufilization of indole by the enzyme did not require L-serine or pyndoxal phosphate, and dld notresnltm net tryptophansynthesis. The activitywas inhibited b;, both snlfhydryl reage~ts and s.ul!hy~r!! compounds, by specific chelafors of copper and non-heme ¡ron (Fez), dithionite and ateb~m. Ate~rm l?hlbItlOn could be preven!ed by FAD. Dialysis resulted in complete loss of enzyme activity, and the dtalyzed mactIve enzyme could be reacÍlvated by the simultaneous addition ofCu2+, Fe2+ and F AD. The data suggest tbat tbis indole oxidase is an ironcuproflavoprotein. 1. Introdnction The most thoroughly studied feature of indole metab-olism is its utilization for tryptophan biosynthesis by the enzyme tryptophan synthase (EC 4.2.1.20) which has been investigated in microorganisms (Y anofsky, 1960; Crawford, 1975), plant tissue cnlture (Delmer and Mills