The Conversion of 3-Indolylmethylglucosinolate to 3-Indolylacetonitrile by Myrosinase, and its Relevance to the Clubroot Disease of the Cruciferae

Abstract

[Methylene-¹⁴C]-3-indolylmethylglucosinolate (¹⁴C-IMG) was converted in vitro to [methylene-¹⁴Cl-3-indolylacetonitrile (¹⁴C-IAN) by myrosinase over a pH range of 4.0-6.0 and this conversion was enhanced by ferrous ions. Other products of the reaction included 3-indolylmethanol, 3, 3'-diindolylmethane and ascorbigen A. Trace amounts of ¹⁴C-IAN were produced non-enzymically from ¹⁴C-IMG in the presence of ferrous ion over a similar _pH range. Furthermore, swede tissues (Brassica napus cv. Danestone) infected with Plasmodiophora brassicae Woron. could convert ¹⁴C-IMG to ¹⁴C-IAN. These results were consistent with the hypothesis that the overgrowth symptoms of the clubroot disease are caused by the conversion of IMG to the auxin precursor IAN.